View Full Version : Panhead Head Problem

11-22-2008, 04:52 PM
I am helping a friend with a Panhaed and we are stumped. Here’s what we have:

The main problem is the front cylinder runs lean, the rear rich. When hot and idling the front cylinder starts puffing smoke (can’t tell for sure black or blue) when it idles. New V-Twin heads were put on that developed scored valve stems and mushroomed valve ends (rocker side) after a few hundred miles. The valves were replaced, valve sets cut and ground, new valve guides installed and new valve seals. The problem still persisted so we ran a air compressor test. With the push rods REMOVED (i.e. both intake and exhaust closed), a compressor fitting for the spark plug and the air compressor set for 50 pounds there are air leaks.

The dilemma is the air is leaking out the heads where the pushrod tubes go. We confirmed this by putting our fingers over the pushrod openings in the head and also with smoke. There is no doubt that air is escaping through those holes with the front worse than the rear. It does not seem to be from the crankcase because it follows the head the compressor/spark plug fitting is in (note: there was always a spark plug installed in the head that was not being pressurized.)

Given the valves, valve guides and seals have all be replaced, what could be the path to allow air to escape from inside the cylinder and come out the push rod openings in the head? Is there another test we can do to narrow this down?

Ronald V. Papasso

11-22-2008, 05:46 PM
possibly air pressure going down past the rings filling cases coming up oil passages to rockerarms? the spark plug situation sounds like intake leak.

11-22-2008, 07:46 PM
Was there any air leaking into the ports? Did both heads do the sme thing? Sounds like another bad valve job or defective castings. Air is leaking into the rocker compartment and its only way out is through the pushrod openings. I know this isn't what you want to here but it sounds like you may need to pull the motor so you can do a leakdown test with the rocker covers removed. Or remove th heads, pull the covers, reinstall the heads, then retest. Dealers choice on wich is easier.

11-22-2008, 07:48 PM
One other question, was any air rushing out the crank case vent?

11-22-2008, 08:25 PM
You have already answered your question. You pressurized the cylinder with the valves closed. Therefore, the rings are eliminated from the picture since the pushrods are out of the motor. You have a leak between the valve and seat or the seat and head.

11-23-2008, 06:19 AM
You have already answered your question. You pressurized the cylinder with the valves closed. Therefore, the rings are eliminated from the picture since the pushrods are out of the motor. You have a leak between the valve and seat or the seat and head.

remove your heads,Did you lap the valves to the seats to see if you are making a good contact, hand lap the valves to the seat make sure you have a ring of contact between valve face and seat,any defect will show up as a low spot not affected by lapping compound,any low spot on seat,seat would have to be recut or depending on depth,hand lapped with different grades of lapping compound,make sure all compound is cleaned off before reassembly,(brake clean works),check your seats are they loose in head,do they spin,or are they tight,are these v-twin heads? also make sure the intake mounts are not loose in head.

T. Cotten
11-23-2008, 10:29 AM
To add to Dan and Ken's scenarios,
It is even possible that there is a breach in the headgasket to allow compression to flow from the chamber up through the drain gallery to come out the pushrod holes.

In other words, the gasket may have "blown" or warped inward without showing on the outside (yet). Removal and inspection of the gasket may be your only means of eliminating the possibility, as well as effecting a repair by re-flatting the gasket/cylinder surfaces. (Eliminating the cause of the warpage, however is a matter of avoiding elevated temperatures in the future.)

With aftermarket heads, anything is possible, so I would suggest testing the removed head on the bench, and corking up the ports to apply strong air pressure to various places while using soapy water to determine if there are any leaks around seats, casting porosities, minute cracks, etc.

I have even found leaks from the chamber and/or intake port penetrating to the headbolt insert in this manner.


11-23-2008, 01:13 PM
if it is a valve not seating it would take the easy route out exhaust pipe or intake manifold.if ring gaps line up it will leak air pressure to bottom end . try removing timing plug. roll motor over using rear wheel to see anything if changes as breather gear rotates. good luck

11-23-2008, 06:56 PM
Thanks to everyone who replied, I was hoping for my friend’s Panhead there was a “solution in a can to fix his Pan”. Sounds like it’s another tear down, which makes the 6th one. To answer some of the questions:

To Brian: Yes, both heads did the same thing, the front more noticeable than the rear with regards to audible sound and smoke. Never checked the crankcase vent to see if any air was moving there. Great suggestion and easy to try before we tear it down.

To Ken S.: The valves were done by a local and reputable Harley mechanic who has lots of experience with Panheads. These are also new V-Twin heads that had to be re-worked after 100 miles due to valve stems scored, valves sloppy in the guides and valve stems mushroomed from the rockers.

To Cotton: Never thought of suspecting the head gasket or the head to barrel surface. These barrels worked with the old (and worn) heads and I assumed V-Twin heads would be quality parts. Give the valve problems experienced after 100 miles, you may be correct “With aftermarket heads, anything is possible”.

Removing the heads and making a fixture to seal them on the combustion chamber side and bench test them may be the best way to isolate the head from the other suspect areas (head gasket, blow by, etc.). One thing that does bother me is that regardless of how bad the valve seats may be, wouldn’t the valve seals themselves hold back 50 pounds of air?

T. Cotten
11-23-2008, 09:18 PM

I do not think that a plate to block off the combustion chamber will be necessary, as air pressure can be applied from the ports with big (#9) corks or stoppers to inspect the seat's integrity and the valves' seal (although the valves will start to open with 20 psi or more.). A plate covering the headgasket surface would prevent observation anyway, unless you have some thick clear plastic handy.

As long as your regulator keeps the pressure constant, any incidental leaks around your fixtureing or valves themselves can be ignored. Bubbles only need a 'differential' of pressure between the inside and the outside to show a breach.

With the pan cover still attached, two (#2) corks can be shoved into the pushrod holes to pressurize the drain gallery for inspecting for other unknown possibilities. Some leakage past modern valve seals should be expected, but not volumes.

I've been there.
It is also a great way to make certain that pan covers won't leak before they are installed; Even pan cover screw holes that have been drilled or crushed through to the intake port show up occasionally.


11-23-2008, 09:38 PM
Cotten...What if the leak only appears after warm up ? Paps

T. Cotten
11-24-2008, 08:03 AM
Cotten...What if the leak only appears after warm up ? Paps

Good point.
Maybe a hot air gun on the head is in order, if no 'smoking gun' is found upon room-temp testing.

A couple of other questions for Ronald occurred to me in my sleep:

If the air is escaping to the drain gallery as I proposed, why doesn't it also show itself at the timing hole? (Early models should have an open path; later models may have the piston over the cylinder hole, especially if the air pressure has pushed it downward.)

Are these aftermarket heads equipped with properly cast-in bronze seats, or short-fused with steel inserts?
(If inserts, do they have Pan-design intake ports, or Shovel, with the Shovel headbolt pattern?)


11-24-2008, 10:55 AM
Thanks again, lots of good information and questions. We went back and checked for air escaping out the breather hose. Each cylinder was brought to top dead center, push rods removed, transmission in 1st gear to keep the piston in place and the air compressor attached to the spark plug adapter, 50 pounds of air. There is a slight amount of air coming out the breather, enough to barely move a flame from a lighter, not enough to move smoke as the smoke tended to dissipate faster than we could tell it was moving with an airstream from the breather tube or ambient air currents. The same setup for the front and rear cylinders was used with similar results. There was still air coming out the push rod tube openings in the heads that would visibly move a column of smoke and bend a flame, much stronger than was coming out the breather. Does this mean what we are seeing is normal?

Here’s some more information, both cylinders compression check at 135 pounds. With the test above, when the 50 pounds of air was applied the cylinder, up on a lift (front wheel clamped), the bike lurched forward since it was in 1st gear. I don’t know if the above information indicates that the rings are good and should not be leaking 50 pounds of air.

Answers for Cotton:

1) Never thought of pulling the timing plug to check for air there. Good idea, will try that next.

2) Don’t know what kind of valve sets there are. They look like silver metal if that differentiates them from having a bronze color.

3) Not having worked on a Pan or a Shovel, I will have to defer the question about the Pan-design intake ports, or Shovel, with the Shovel headbolt pattern to the person I am helping since he has worked on both. They are V-Twin heads for a Panhead if that will answer the question if you know what V-Twin sells.

With regards to the bench test we were proposing with blocking off the combustion side of the head and pressuring the head, we thought we could use soapy water to check for air bubbles around the valve stems and the top of the head. For the amount of air coming out the pushrod tube holes the assumption would be one leak, not many small leaks that would each not significantly show bubbles.

As for heating the heads up, they are cold when we are doing these tests. If there is a leak due to valves, seals or a crack, it is already showing up cold.

More to do, more to think about before the tear down. Keep those cards and letters coming!

11-24-2008, 08:45 PM
when you pull the heads take note if any of the head bolts ( especially those on the left) are oily, this will give some indication if the gaskets are sealing good or not. Check the valve seating with a little prussian blue after you take the heads apart. If the seats are in good sealing order I don't see much use in pressure testing the ports as the pressure from the original test would not have gotten past the valves and into the ports. I would be looking real close for cracks or porosity in the heads ( especially since you stated thier origins). A good rough check for this would be to re-assemble the valves in the head, set it on the bench chamber up and fill the chamber with denatured alchohol. then start looking for wet spots were the alchohol seeps through. Don't be afraid to let it sit a while to be sure.Remember during combustion, presures of thousands of PSI are at work to force gases through the smallest porosity or crack. Good luck.

T. Cotten
11-24-2008, 09:29 PM

One step at a time, slowly lest disassembly gets ahead of us....

When a head comes off, inspect both sides of the gasket immediately between the drain hole and the combustion chamber. If it is intact, with no discoloration, without even oil passing, then my first theory will seem unfounded. Grinding the headgasket surfaces to flat will display any gross distortions that may also have occurred.

On to pressure testing BEFORE any other disassembly,
Blocking off the combustion chamber will not only be a lot of effort, you cannot see the entire ports or valve seats clearly anyway.
But no doubt IF you see cracks in the intake from the pressing of a hardened seat, then bubbles would be, uh,... anticlimactic, for want of a better word.

On to seat materials, there are very damn good reasons why the Factory didn't put steel seats in Panheads.
The port alignment with a headbolt pattern change allowed them to be used in Shovels, although marginally, as many of have witnessed.
The geometry of evil evo's overcame the problems to an even better degree (every pun of 'degree' intended.)

I have no idea what V-TWIN heads have in them, but STD wasn't stupid when they produced their premiere replacements as Shovel hybrids, even though it didn't do the vintage scene any justice.

Looking forward to your observations,


11-26-2008, 09:07 AM
I am for moving slowly but my buddy’s patience is getting slim as he has already pulled the tanks in preparation for a tear down (again, #7). I have not gone back over to repeat the pressure test with the timing plug removed. I also want to verify the air coming out the front head follows the compressor fitting in the front head. If the crankcase were being pressurized I would expect to hear air rushing out both heads regardless of which cylinder is being pressurized.

I also got another piece of information, when the bottom end was rebuilt it was rebuilt with 80” flywheels. Don’t know how that affects anything but it is not a stock panhead bottom end (53 or 55, I forget) anymore.

Given the faulty valve guides and valves have already been replaced, checking for cracks in the head from valve guides would be easy to do once the heads are pulled. With regards to the gasket surface I think we can get an idea of the flatness using a flat surface such as a window pane or granite block (thinking out loud here). With the head on the flat surface and a flexible high intensity light through the spark plug hole and rotating it 360 degrees we may be able to see light escaping from the gasket surface if it is warped or uneven.
Thanks again for you help, should have some answers over the holiday.

Ronald V. Papasso

11-26-2008, 12:02 PM
just a thought is there a slight crack anywhere that may open up during heating or a porous spot somewhere.

just thinking out loud


11-29-2008, 05:46 PM
Went back to do some diagnostics on the Panhead. The test results were different between the front and rear cylinders. First off, we pulled the timing plug and can confirm the crankcase is being pressurized when the cylinder is pressurized. Enough air comes out the timing hole to blow out the typical BIC lighter. This was the same with both cylinders.

What differs is when the front cylinder is pressurized (50 PSI) air is clearly coming out the push rod tube openings in the front head, nothing out the rear head’s pushrod’s openings. When the rear cylinder is pressurized, minimal air is coming out the front or rear head pushrod tube openings, too slight to really tell. The problem seems more severe with the front cylinder and head.

Thinking the rings are leaking, we put oil in the front cylinder and pumped it a few times to get the oil on the cylinder walls. The result was the same, pressurize the front cylinder and air clearly comes out the front head push rod tubes, not the rear. If the leak were from pressurizing the crankcase and that air working up an oil passage, I would expect the same results on the front head when the rear cylinder was pressurized. The problem seems to follow pressurizing the front cylinder.

I am assuming we can rule out bad valve guides and cracks around the valve guides because the push rods are removed hence the valves are shut. Given this is a fresh (less than 200 mile) run in since the valve seats were cut and ground there should be no air leaking past any of the valves to then leak out a guide or crack near a guide.

I don’t know what to conclude from here, possibly damaged rings in the front cylinder letting crankcase pressure through or a crack in the front head. Before tearing it down, anything else we can check to confirm it is not rings? Compression test showed 135 pounds when last run before doing these air compressor diagnostics. Remember that these air compressor tests are with the engine cold and if they are showing up cold, it gets worse when hot.

11-29-2008, 07:48 PM
Before determining a completely faulty head, check the location of the ring gaps. If they are all aligned with each other ??? Problem solved. Paps

11-30-2008, 06:00 PM
Starting to sound alot like a bad headgasket. Air to the oil passages would pressurize both the crankcase and the rocker box. At 200 miles the rings may not be completely seated yet. That may also explain some of the leakage to the crank case.

11-30-2008, 07:32 PM
I have been following this thread with great interest . A friend had very similar issues with an evo. ( fresh heads but smoking and running poorly). Long story------- finally found the ring gaps were lined up. If I was betting,this is where i'd put my money. Also, If your guides and stems failed after 200 miles, who's to say that your cylinders didn't also suffer some damage. Do yourself a favor. Go ahead and pull those jugs off.
Now I'm going to make a big mistake and tell how I stagger the rings. The gap on the oil expander is lined up with the wrist pin.or at 9:00 o'clock The bottom "scraper" rail is at 7:30, Top rail at 10:30 Top ring at 1:30 second ring at 4:30.
Now,what causes the rings to line themselves up is a complete mystery to me and after 40 years of tinkering with engines of all types ,this Evo was the first time I have actullay seen it. I do however understand that it is common, especially with supercharged racing engines which commonly run 30 plus pounds of boost.

11-30-2008, 07:42 PM
I try to keep the gaps off the thrust faces myself.

T. Cotten
11-30-2008, 08:02 PM
Installing the rings spaced is certainly prudent for start up, but if the rings do not rotate in service, then other problems will quickly develop.

(Flatties have the problem of one side of the cylinder distorting more from heat than the other, but still the rings move where they can.)

A line of gaps would allow easier entry for pressure to the crankcase, but it would not explain air out the pushrod holes of only one head.


Please remind us what year we are dealing with: Early Pans have the head through cylinder drains connected between cylinders in the case gallery, dumping upon the flywheel at the rear. So air to one can easily come out the timing hole as the other.

Please don't assume you can rule out anything until you have dissected it!

"Never does only one thing go wrong at a time." .... Ridnick Wysdom


11-30-2008, 09:29 PM
I just read thru this entire thread. I have a few observations I like to offer up here. I'm not trying to argue with anyone here. There could be typos in messages that completely change the intended meaning. I just thought it might be useful to have a review at this point and write down a few points that have been made.

Assuming there is a compression leak somewhere...

-The port escape route was mentioned early in the thread by t-bone and everyone seems to have ignored it. Leaks into the ports would vent out to atmosphere. Forget valves, seats or any leaks into the ports. They are the same as venting to atmosphere. Those two big holes called intake and exhaust manifolds would relieve any pressure from a leak.

- Somebody mentioned valve seals. Assume we are talking about a leak from the cylinder into the ports and up the guide and out the seals. Forget it. Even if such a leak existed, even if the valve seals were missing, the air would go out the ports. Forget valve seals. They are not at play here.

-Motorhead said that the rings were eliminated because the pushrods are out and the valves closed. Actually, that tells me that the rings are a primary suspect, NOT ELIMINATED. The pressure should be held within the cylinder, which is between the top of the rings and the closed head. Escape routes which were mentioned were
head gasket leak into oil gallery
ring gap alignment causing leak into crankcase
head cracks into the oil galleries
There is another possibility. First, I have no experience with panheads. If there are oil return lines in the cylinders, and the head gasket suggestion tells me there are, a cracked cylinder wall into one of those returns would pressurize the rocker area as well as the crankcase, and would definitely get worse with temperature increase. It could also allow oil to enter the cylinder and subsequent smoking, more so when hot and the crack is more open.

Whether a cracked jug, or leaking headgasket, when it pressurizes the rocker arm area the path of least resistance is the pushrod tube holes in the head. The reason it does not come out of both sets of pushrod tube holes in both heads is because the pressure is relieved out the cylinder with the problem via the pushrod tube holes. There is not enough flow (volume of air) thru the leak, which acts like an orifice, to pressurize the other cylinder via the oil gallery or the crankcase. Too much volume required to fill the crankcase and then flow up into the oil galleries of the other cylinder.

So, now, after saying motorhead was wrong about the rings, I'm going to backtrack and say I don't think it is the rings. If it were the rings, then the air leak would go down, into the crankcase until it filled and then the air flow would run up the oil galleries of both cylinders and I would expect equal flow out of both heads at the pushrod tube area. But we have flow only out the PR tube holes on one head. That tells me the leak is very near the rocker area for that head and the path in the other direction is long and/or restricted. For that reason, I am leaning toward a head gasket leak since it will spill right into the rocker area and vent out the PR tube holes before preventing it from pressurizing the rest of the engine and hence the rear head. If the head gasket is not leaking, then a cylinder crack or head crack into the oil area and NOT INTO THE PORT AREA.

-There was no mention if pressurized the rear cylinder created a flow of air out the front PR tube holes. I would not expect it on a good rear cylinder since the only leak would be minimal thru the rings and it would only result is a slight breath of air escaping anywhere there was a large opening like PR tube holes. If you do that test and no air comes out either the front or rear PR tube holes, the rear cylinder is not the problem.

- Original post identified two problems. Lean and rich cylinders and smoke. Okay, 3 problems. Before we start telling people to tear apart engines, shouldn't we try to identify if the smoke is black or blue? Are the plugs oil fouled in either cylinder? Is there a white hot plug and a sooty black plug? How do we know one cylinder is running lean and the other is rich? It's a single carb engine. So if one is truly lean and the other is truly rich, isn't it safe to assume that one cylinder is running badly due to carb issues and the other due to another problem? If there are dual exhausts on the bike the rich pipe should be black and the lean pipe should be clean. But assuming it is a two into one, let the plugs tell you what is going on combustion-wise.

And please, before you tear the engine down, make sure you don't have an intake leak on that lean cylinder. Somebody already mentioned this. Tell your buddy to cool his jets and think thru this, instead of diving into the motor. If your car quits on the highway, do you yank the engine or do you check the gas gauge first?

Last comment on smoking. If it is blue smoke and only at idle, does that not point to valve guides and seals being bad. Completely unrelated to the pressure leak issue. But worth looking at. Again, look for oily deposits. If there are none, I would not think you are burning any oil. You are running rich on one or both cylinders. Dry soot on the plug is the telltale for rich.

Good luck. I hope you have a bad head gasket and an intake leak.

12-01-2008, 01:22 AM
I re read the original post to be sure. He says both heads are leaking from the push rod holes. The front is worse than the rear.

12-01-2008, 03:52 AM
Panhead In Question Is A 1955

12-01-2008, 09:02 AM
I think Brian has the right idea. Just something I ran into once. The counterbore on the head was not deep enough for the cylinder spigot clearance, wouldn't alow for full copression of the gasket. Easily solved by removing material from cylinder.

12-01-2008, 11:04 AM
A lot of questions and places to revisit. I will address these and see if it helps clear up some of the work we have already done and fill in some gaps in what I may have left out.

We did pressure test the intake manifold by removing the carb and plugging the carb hole with a rubber plug and adding 25psi. With our rudimentary equipment the intake manifold and intake valves seem to hold pressure. Note to anyone trying this: Make sure you bleed the pressure from the intake manifold before prying out the rubber plug. With 25 PSI it comes out with so much force if you don’t duck quickly it will knock you unconscious!

The exhaust was a little harder to diagnose and with the cylinder pressurized and using the flame/smoke test, there does not seem to be any air moving out the exhaust on either cylinder.

With the pushrods removed, both intake and exhaust valves closed and good valve to seat seals, the ports, valve guides and valve seals should be blocked from any air. We agree, valve guides and seals are ruled out.

Rings are high on the suspect list and right now we have no way to know if the gaps moved from where they were set until the cylinder is removed carefully to not disturb them. The cylinders do have an oil return passage from the head to the base of the cylinder with a small hole in the cylinder. This is also a suspect area if the front rings are leaking pressurizing the crankcase and allowing air to come up the return passage in the cylinder back into the head.

Relative to the air coming out the timing plug, the air coming out the pushrod tube holes in the front head is much weaker than that at the timing plug. The air coming out the timing plug blows out a flame, the air coming out the front push rod tube holes merely bends it.

A head gasket leak was dismissed until someone posted that the counterbore in the head may not be cut deep enough. Given the front cylinder has been re-sleeved, this is highly suspect now. Had never considered this and this has moved high on the list! This engine has had the heads pulled at least 6 times and even though the gasket has impressions on it, they may not be deep enough to seal. Great idea and a place that was never looked at or considered!

It appears that only the front head has this problem when the front cylinder is pressurized. The rear head when pressurized does not seem to move air out the rear or front pushrod tube holes in either head. It flows only out the front head pushrod tube holes when the front cylinder is pressurized.

The cylinders do not run the same when the plugs are looked at. There are dual exhausts on the bike and the front exhaust builds up smoke at idle and then blows it out when the RPM is increased and then clears. The rear cylinder does not do this but the best idle is obtained when the front cylinder hits evenly and the rear gets a miss every 3rd stroke. The hotter it gets the worse the smoke problem is at idle from the front cylinder even though it is hitting evenly. Can’t tell for sure if the smoke is blue or black, it has been observed by many people and it’s not clearly black or blue. I’m close to color blind with poor color perception so I can only tell you its some dark color and have to rely on the other observers for the color, which no one agrees on.

When the heads were pulled there is carbon on the rear piston and the front piston was clean enough to eat off of, looked cleaner than when it was first installed. This made us suspect the front cylinder was running rich and washing out the carbon. The intake manifold was suspect and was not real tight so it was lengthened, new O-rings and clamps installed. Now the front piston is starting to build carbon but the smoke problem still persists. Given the intake manifold to the intake valves is holding pressure we think it is sealed.

It was the smoke trail and uneven plug burning that lead to the following work:

1) This was a fresh rebuild including cylinder boring, new pistons and rings, valves reground with the original heads.
2) The original heads starting getting noisy and it was found the valve guides were starting to split. This was attributed to many things such as the valve seats being cut too deep causing the valves to go up father than they should, valve guides not pressed in as far as they should or valve guides too long. Since the heads were old and starting to get loose rockers, new heads were installed.
3) With the new heads everything was good until a few hundred miles, the spark plugs went from burning even to the front one being oil fouled. Another tear down found the front piston was 0.020” loose in the bore when measured with a flat feeler gauge on the front face, it was that bad. The front cylinder was re-sleeved and bored to match the rear. New piston, rings, etc. were installed in the front cylinder.
4) This is when smoke from the front cylinder started to appear so the heads were pulled again. This is when the new heads with 200 miles on them had scored valve stems, valves wobbling in the guides and mushroomed valve stems. New valves, valve guides, and seals were installed and regrinding was performed on both heads. This did not change the symptom and the front cylinder still would smoke at idle and clear when the RPM went up.

Given the above and all the great responses from everyone, the best suspect area is the counterbore in the head or the re-sleeved front barrel is not correct causing a poor head to cylinder fit. This is an area we had not pursued at length other than a casual observation.

Having gone though many top end tear downs and finding something it appears we have overlooked the head counterbore to cylinder fit, especially since the re-sleeving. What is the best way to check the fit of the cylinder to head counterbore? If somone can attach some numbers to it or observations then we can check that more accurately.

There have been many problems we have sorted through and many red herrings along the way and this may be the “smoking gun”, how apropos.

Ronald V. Papasso

12-01-2008, 11:39 AM
Couple of comments on your feedback.

I would not expect a rich cylinder to look clean unless it was not firing at all. Rich means incomplete combustion and that means carbon. The only way a piston would get "washed down" is if the plug was not firing at all. You are not going to have some gas burn and the rest just splash around in there. If you had so much gas that it washed down the cylinder, the cylinder would miss a lot and probably not fire at all and just flood.

If the air flow is more pronounced out the timing hole, then I lean towards ring gap or maybe a broken ring.

You might have more than one thing going on here. The counterbore/spigot issue should be checked as well.

Regarding the smoke, I have to go back to plugs and deposits. If you are burning oil, it will show up as an oily sooty deposit on the plugs, head and piston dome. If you are running rich it will be dry soot. I also find it hard to believe you cannot tell the difference between blue and black smoke, unless this engine is running rich and burning oil. Blue smoke is very obvious to see. And if you stick your finger into the tailpipe, it should have some oily residue if you are burning oil. Even if you are totally color blind (I'm red/green) the smoke would appear to be gray if oil and black if gas.

I mean no offense here, but from some of the "theories" you and your buddy have had, I get the feeling you are not experienced engine mechanics. There could be something very obvious here that you are not seeing and hence reporting. You might have several things wrong with this engine and the combined symptoms are taking you all over the place.

I'm inclined to recommend you take this to someone who does this for a living. It will cost you a little and that might be a problem. But it could also save you a bundle if there is something else wrong with this engine that will do even more damage.

12-01-2008, 12:40 PM
Not offended by your comments, we are amateur mechanics (especially me) and I am often referred to as having “office hands”. I am new to this and if the parts fit and everything works properly, I am a great mechanic. If they don’t, then I am lost and have to seek help from those more experienced. The amount of help I have received from this forum alone during those times has been exceptional. Debugging from long distance is an art form and part physic of which I have greatly benefitted from both.

The owner of the Panhead has been in this hobby for over 30 years and has lots of experience but not enough to debug this. As for the local mechanics, they have made mistakes on this engine and they have corrected their mistakes and provided lots of guidance. We may have stepped outside their comfort zone since the stock ’55 engine was rebuilt with 80” flywheels, high lift cam and non-stock heads. This may be something that they do not want to get intimately involved with other than the piece work they have done.

As you can tell we have had many things going on here and have tackled them one at a time. To say we are lost and traveling around in circles would be an understatement. These posts came about because we needed to put the wrenches down, sort things out systematically and seek help outside of our pool of knowledge.

The question of black and blue smoke is still a debate. I have put a clean white cloth over the front exhaust and the residue appears black and dry. Inside the pipe, about 1” in, you can pull out on your finger tip an oily black substance, even after the pipe was cleaned with lacquer thinner and run for a few miles. To me this is oil, to others this is unburnt gas mixing with the carbon. I do not have the experience to enter that debate but have always questioned how you can have carbon build up in the pipe but not on the piston.

What is not debatable is on the last tear down after running the engine for 200 miles. Prior to removing the heads there was no doubt the engine was idling without a miss on the front cylinder and a miss, every 3rd stroke on the rear. Great top end, just an uneven idle. No matter how we tweaked the low speed needle we could not get the miss out of the rear cylinder. At both extremes, lean and rich needles settings, the mixture was off so much the engine would not idle at all. This was repeatable all the time. The best idle was with the front cylinder hitting every time, the rear missing every 3rd.

When the heads were pulled, the rear piston had carbon on it and the front piston was 100% shiny, no signs of carbon on the piston at all. This may be a sign that has nothing to do with the problem at all but another red herring.

The front and rear spark plugs are not showing signs of oil which is why we are suspecting it is not oil. The plugs are not burning the same and I forget which is rich and which is lean. This is how we got to this point, visible smoke from the front cylinder, no signs of oil on the spark plugs but one cylinder rich and one lean plus an uneven idle.

Your advice on seeking help from a professional is well advised and is up to the owner of the Panhead how far outside of our local area he wants to go. Thanks again for your input and no offense taken, appreciate the help, opinions and anything else you can muster.

Ronald V. Papasso

12-01-2008, 01:45 PM
Now I'm going to make a big mistake and tell how I stagger the rings. The gap on the oil expander is lined up with the wrist pin.or at 9:00 o'clock The bottom "scraper" rail is at 7:30, Top rail at 10:30 Top ring at 1:30 second ring at 4:30.

is that all am or pm and that an awful long time spacing out each ring

just thought I'de lighten it up a little

12-01-2008, 03:00 PM
If the piston ring seal is not equal in both cylinders, then they both will have different fuel mixture requirements. You could say that you have a low compression single cylinder engine up front and a high compression engine out back. As the engine RPM increases, I would expect the leakage around the rings to have less impact because the speed of the piston would make up for the leakage to some extent. The velocity of the gasses coming thru the intake is much higher and hence the leak has less effect. You are also using a different fuel circuit at a higher engine speed. You might be adjusting the carb to provide the perfect mixture for the air flow into the front cylinder and since the mixture is coming from one carb to both cylinders, the back one will be off a little. This could account for the occasional miss on that cylinder. You would not be able to tune it out without having an effect on the front cylinder.

So, there is a chance here that your lumpy idle and your measured front cylinder air leak are related.

I've done a lot of troubleshooting for big power plant equipment, mostly gas turbines. All I can tell you is when you have mutiple problems/symtoms, you have to address them one at a time. You can fix mutiple known problems at once, which makes sense when you are tearing things apart. But you will never truly know what caused your observed problem. If you suspect a leak in the front cylinder, make sure you fix that problem. While you are in there, look for anything that could be wrong. Compare the old heads to the new heads. Look for other telltales of something acting up. It's really hard to sit far away and be able to tell somebody what to look for. Often seeing something will point you in a direction that you would not have considered. Nothing beats being there with the equipment.
As for the smoke, could be the rings have not properly seated in that front cylinder yet. Are you running synthetic oil? I would not recommend it for break in. Put regular oil in for the break in.

Good luck.

12-01-2008, 03:59 PM
This would all be PM as I am not a "morning person".

somthing else-- did you check the ring end gaps when you installed the new pistons?

12-02-2008, 10:31 AM
This will be the last installment since we did find something overlooked and will need some time to either fix or replace. When the head gasket was removed the piston had absolutely no carbon on it, still don’t understand how the piston can have no carbon and be absolutely clean but it is. The surprise was the bottom of the head gasket has wet oil from the oil return hole to the cylinder. There was even a small wet trace of oil from this location on the head near the spark plug. If the head is tight and the gasket sealing we would not expect traces of oil under the gasket with a trail inside the head.

The head counterbore and cylinder spigot were measured. The head counterbore is not consistent and varies by 0.010 around the head but is still 0.004 deeper than the tallest wall of the cylinder spigot. Given the head gasket is around 0.028” thick this should not be a problem.

What is a problem is the head rocks left/right on the cylinder with no head gasket. The rocking is so bad we can get an 0.020” feeler gauge between the head and cylinder on the outer mating surface if rocked to the extreme. Given the head gasket is 0.028” thick, it is doubtful the gasket is being sufficiently compressed in that area. If you are familiar with this year panhead there is only about 1/8” of gasket between the oil return hole and the cylinder. This is the area that does not appear to be compressed.

We put a straight edge on the head and the straight edge does not fit flat across the head near the intake bolt hole, it rocks left/right. The high point seems to be the bolt hole itself. Even more curious is the bolt hole near the intake is not as deep as the other bolt holes and the head bolt is around ¼” higher in that one hole relative to bolts in the other holes.

Everywhere else on the head appears flat. It was harder to measure the flatness of the top of the cylinder across the bore due to the raised spigot but walking around the bore there were no signs of rocking with the straight edge.

This is not so obvious when the head gasket is on. Since these heads have had so many defects when purchased new I do not know what the owner will decide, replace the heads with another brand or continue to sink money into these heads assuming this is the last problem with them.

One more thing, the ring gap was checked and correct prior to installing them.

12-02-2008, 01:58 PM
OK, I lied, one more installment, I just got a call with an update…..

The rear head rocks also when it is placed on the rear barrel without the gasket the same amount as the front. A set of old stock heads were borrowed and placed on the barrels and they do not rock at all, they sit flat with no movement. Unless we are way off base, heads that rock side to side do not sound like they will seal properly to the gasket.

12-02-2008, 03:26 PM
Warped heads = not good.

Although you've already proven it's the heads and not the jug decks, for future reference if you wanted to check the jugs for flatness, put them on flat plate and then put a dial indicator on the deck surface and with the magnet off, run it around. It will also show you if the base flange is parallel to the top flange.

I'd also be curious if the heads had the same volumetric capacity given all the other "issues" they've had.

If you saved all the parts that you had to replace, I'd bring them back and show the dealer. He might take them back. Or, he might give you some of your money back and let you keep the heads. Then you can take them to a shop and have them machined flat.

If it were me, I'd try to get my money back. Then I'd search for a set of original heads and rebuild them. Try reputable shops that won't sell you their junk heads. I can give you a name in upstate NY that all my friends with panheads swear by (not at). He so busy his wife answers the phone and unless she knows you, won't let you talk to him. He calls you back later when he gets a moment. He's also built some heavily modified panheads so your flywheels and such won't bother him. He might even give you a few tips. He might even be willing to save your tired old original heads.

12-03-2008, 03:57 PM
Well I admit, we made a rookie mistake but a lesson well learned. In the future when I am fitting any gasketed surface, fit them without the gasket first to see how well they mate. Never assume that if it’s shiny and right out the box it is a good part.

Thanks for the tip on how to measure the flatness of the barrels. I do have access to a granite slab and dial indicator here at work. It sits in the dusty corner of the electronics assembly room and I should make use of it more than the company does.

Returning the heads has not been successful the first time it was found the valves were scored, valve guides loose and valve stems mushroomed. The middle man that they were purchased from said he called the distributor/manufacturer and they could not be returned or pro-rated since they had been used although briefly. When the distributor/manufacturer was called directly they would only speak with their point of sales, not the person that purchased them 3rd party. This is why they were not returned at the first sign of trouble.

The owner of the Panhead is a member of the AMCA and reads the forum. I have been doing the writing because he is a man of few words and felt I could describe better the events and paths we have taken. We both appreciate the offer you (Rob) have made to put him in touch with someone that you highly recommend in the NY area. The next move is his deciding where his time and money is best spent with resolving this head problem.

Thanks again to everyone who took the time to provide very useful suggestions. Had we not gone down the paths put forth I don’t think we would have discovered the heads were not flat. Thanks again.

Ronald V. Papasso

12-03-2008, 05:05 PM

I'm going to repeat myself from an earlier post. "Do yourself a favor and pull the jugs off."

Its only 8 more fastners and a couple of gaskets. Take a good look at those rings. (enter your cliche' here) Better to be safe than sorry.

Dennis Rousseau

12-03-2008, 05:49 PM
Scored guides and mushroomed stems sound like faulty parts to me. Just the stems would have told me I was sold junk parts.

You can always try the small claims court route. Might make the dealer rethink his first rejection of your claim.

I think in an early post you said these were from V-Twin. They have an email address for info on their website. info@TeddCycle.com A well worded email explaining your problems and the pain you have suffered just might find it's way to Tedd. Can't hurt, that's for sure. Squeaky wheel and all that stuff.

Are you sure they are really V-Twin parts? Any chance the dealer sold you parts made on Melmac by aliens? Threat of small claims court might get his attention. And if Tedd's parts say V-twin on them in the casting and yours don't, hmmmmm. Go after the SOB.

We had a shop that opened up locally. Bunch of jerks that must've watched too much American Chopper on Discovery. Did a lot of bad work, took money and never completed work. Lasted less than a year. Not sure what happened to them, but would not be surprised if they were buried somewhere next to Jimmy Hoffa.

Good luck,

12-10-2008, 02:33 PM
For some reason while I was in the shower this morning I was thinking about your problem. I realized that I told you to check the flatness of your jugs on a surface plate with an indicator. It occurred to me that there is a spigot at the bottom of the jug. The spigot would require you to rest the lower jug flange on a set of ground parallels to be able to check the relationtionship between the bottom flange and top flange. If you don't have a set of parallels to use, you might try finding a piece of cold rolled square or rectangular bar stock of suitable thickness to allow clearance for the spigot. Lightly flat file any dings away. Then check it with a micrometer to see if it is parallel. I would think that a new piece of cold rolled would be parallel within 0.001 inch and should be fine for what you are doing.

And, after you check the top flange, flip it over and check the bottom the same way. If the bottom is warped so that it creates a gap between the bolt holes, the parallels will rest on the high points and you won't pick it up when you check the top.

Sorry for the oversight. Have a jug sitting right in front of me so no excuses other than misfiring synapses.

12-10-2008, 02:54 PM
We have not pulled the jugs yet and I did not remember the bottom of the jug is not flat either! Thanks for the suggestion.

Ron Papasso

12-14-2008, 06:22 AM
old rust better head to the library ....http://i69.photobucket.com/albums/i71/flthead/book.jpg

12-18-2008, 06:50 PM
Nice work!!