View Full Version : Cylinder head fin repair/Recommend

10-03-2006, 08:46 AM
Please recommend the person that can do a quality job for me. I have '30 Chief heads with thin fins broken off.
Thanks for your time.
Tom Pribyl

T. Cotten
10-04-2006, 09:08 PM

I have associates that weld up fins from scratch and then carve back to conformity such as shown in the attachment.

T'aint cheap, of course.

Post me direct at liberty@npoint.net


Tom Lovejoy
11-22-2006, 10:57 PM
Hi Tom , Tom here - check with your local welding shops. If your lucky you'll have a guy in town who does it all the time. Theres a guy here in L. A. - a large welding shop, he has a bucket full of busted Harley fins. He welds on the new fins and then you take your part back home and shape it to fit the way you like. Its a slow process and alot of work with a dremel tool, but they come out quite well and you will hopefully save some bucks too.
Just ask around and try to find a welder who likes or has an interest in antiques - it worked well for me good luck.

11-29-2006, 03:00 PM
Hi,I've heard of fins being rebuilt by braising them up and then grinding them to shape.Has anyone done this-any feedback,thanks.

11-29-2006, 05:01 PM
I had some fins repaired with chips taken from old lawn mower engines with cast iron cylinders. You could probably use air compressor chips also. Just find cast iron cylinders with close to the same thickness as your cylinder fins. Hammer a chunk off close to the size you need. Grind the cylinder fin are to shape. Shape your replacement chip to fit that area. Bevel both sides of the chip for welding. They were arc welded on using a nickle rod electrode. I think the rod is called Ni-Cad. Blending the seams in was easy. Painting them hid the discoloration. Paps

T. Cotten
11-29-2006, 08:11 PM

The term "braising" usually refers to flamewelding ferrous (iron) and cupric (brass and bronze) metals. So with castiron heads and cylinders, your term is correct.

As I posted, the very best results are when the fins are built up entirely from scratch. But it is time con$umeing, and demands arti$tic $kill$.

Tacking on broken shards from other castings invariably results in porosities and blemishes deep between fins.

So the very best results cost much more, of course.


11-29-2006, 10:53 PM
I agree with you Cotton but if the fit from one piece to the other is good and the weld bevel and fusion path are small, the porosity looks more like natural casting pores. Building up small chips works for me on fins but building up large missing chunks in fins will create to much heat distortion on the whole cylinder IMO. I assume he wants the fins repaired for cosmetic reasons rather than funtional ones. I presented him with a economical alterative to this repair. Of course it will depend on his needs what route he will go. Paps

12-02-2006, 04:03 PM
Paps--that would be NI-ROD. Two versions exist for welding of cast iron. Ni-ROD 55 and NI-ROD 99. The numeral designates the nickel content of the rod or wire.

12-02-2006, 05:30 PM
Thanks for the correction swall. I wasn't sure if my memory served me well, and on that sense I was correct. ;) Would you recommend the higher nickel content rod or the lower one for cast iron ? Paps

T. Cotten
12-02-2006, 07:09 PM
Just for perspective and the sake of friendly discussion:

Custom-fitting shards requires a lot of tedious time and effort, which means a lot of money if you have a pro do it. And they better be perfectly vertical and spaced, or every grindmark will show like a 'cats-step". Touch-up welding means even more expense, doubled by the finishing after that.
Porosities exist in original castings, but it doesn't take an expert to spot lines of big'uns.
And porosities don't conduct heat very well.

As a veteran dumpster-diver, I found it is gol-durn hard (I hope that gets by the censor) to scrounge up shards that match in color to different matrix castings.
Eyebrows raise when they do not.

So dollar for dollar, building up the fins from scratch gives the best result for your money, as it most often is less labor charge in the long run.

If you can do it yourself at home, you might be ahead of the game.


12-02-2006, 11:07 PM
Always friendly in discussion...:) Why match the iron colors if the cylinder is to be painted Cotton ? Matching shards isn't compilcated. Holding them in place for welding isn't either. Clamping takes care of that. 100% contact isn't neccessary either. Protecting adjacent surroundings is pertinent but that can be done with non stick welding coatings. A good welder is needed though. He will leave behind very little porosity. Most of his porosity will look like foundry mold sand surface. One pass on top and one pass on the bottom will bond the piece in. Grinding off the excess is tricky. A steady hand is needed whether you weld in a piece and grind it off. or whether you build it up and grind it off to blend it in. Neither repair suggested will do any good for heat dissipation. That is because, neither repair material used in welding in a chunk or building it up are parent metals. Botton line is...if a person doesn't feel he can do the job himself, he should seek out one who can. Now this is where the cost goes up. My point mainly on the suggestion of adding a chunk is to keep from subjecting all of the machined surfaces, including the bore, from warpage due to excessive heat. Paps

T. Cotten
12-03-2006, 09:57 AM

I forgot that '30 Chief heads were castiron, and not aluminum,....shamefull since I have a set of those on the bench that had six or eight fins replaced.
The were not originally painted, but nickel'd. Electroplating magnifies blemishes and texture differences.

(I guess I was addressing fin repair in general. Since I rarely get my own hands dirty at it any more, its all general to me.)

When I offered sawn castiron blanks from which to cut replacements, my welder quickly pointed out that the fins were often too close together to allow it where the breakage was "deep".
Porosities seem to be a function of access for the TIG tip, and if you can't get to the seam directly, your gonna have some.

So he built them up with silicon bronze with less effort. Which means: cheaper.
(As if anything is cheap any more. No matter how you repair fins, it is never "cheap").
Your are right, Paps, matching shards isn't complicated, but it is tediou$.
And you will have to dress them a lot anyway.

Sculpting from scratch is easier than most folks might imagine with simple 'whizzer wheels' and flexible abrasive discs on a diegrinder (such as normally used upon a 4"grinder). The width of the wheels helps keep things "linear" while allowing access into the deeper valleys between fins. Occasionally we mount the discs on a fixed arbor and hold the castings to them.

Our textureing starts out (and sometimes finishes) with the "Outlaw's Friend", which is a coarse, pitted, and broken grinding stone with a stick through the center for a handle. Random strokes give a very convincing character. Burnishing with coarse wire wheels can also smear grindmarks and add cast appearance, if applied with abusive malice!
(We have the luxury of a spare blast cabinet filled with steel shot for a final finish.)

Distortions are a fact of life. All heads (and cylinders ) should be flattened (or bored) after welding, naturally.
And since nearly all castings need these operations as a matter of course, it really is not an additional cost.
The amount of heat a casting incurs during welding is always a function of the welder's patience: Ya gotta do something else between beads.
Many castings should be pre-heated anyway.

I have a large stash of re-claimed finnage that will never be used: too much trouble only to get an imperfect result. Will trade for gearshift knobs or valvestem caps!


12-03-2006, 10:44 AM
I am glad you brought the shot peening up Cotton. It is a wonderful tool. I agree totally on your plating explaination as well. Heat is at the welders discretion. He has to apply it correctly, distribute it evenly, spread it consistantly, and cool it properly. His goals are penetration, maintaining tempers, relocating molecules, and last but not least...appearance. Welding is a very noble and highly skilled trade meant for a select few. Almost anyone can fuse metals but can they do it right ? You mentioned the die grinder etc., don't forget the trusty ole file ! ;) Paps

T. Cotten
12-03-2006, 11:58 AM
Ole File?

That must be why its called the "Swedish Mill"!

As I mentioned on other forums, I flatten heads and cylinders on my "Polish Mill" (See attachment). It stays still while the 'operator' runs around it.

The lower stone (under the tabletop) is 42" and actually cuts too fine a finish. The white blanchard stone is used to dress the others.
Not only is set-up time eliminated, but metal removal and geometric error is reduced to an absolute minimum, with zero chatter or toolmark.
Heads and cylinders almost "wring" together, as even clamping distortions are eliminated.
Low-tech rules!

But frankly, I haven't encountered any unusual warpage of heads from even extreme weld repairs. Motorcases, however, are a nightmare.


12-03-2006, 01:23 PM
Paps--the use of Ni-Rod 55 or 99 is a trial and error thing. Also depends on whether doing stick welding or TIG welding.

12-03-2006, 01:42 PM
Another thought on cast iron fin repair--if you are going to braze or use Ni-Rod, the replacement piece need not be cast iron. Just use a piece of steel sheet. Of course, some of Cotton's tricks will be necessary to try to get a good texture match of the surface finish. I am thinking (more like musing) that some sort of flame spray coating on the finished product might be used to produce a casting like finish.

12-03-2006, 10:59 PM
Some interesting information on fin repair. I just did several fin replacenents on my 36 indian 4 heads and cylinders. I found some good fins on a air compressor head. My repair turned out good. There is a stick welding rod where only a slight preheat is necessary. I don't have the name in front of me, but it worked for me. It is rather expensive. After the weld I put the part in a bucket of sand to cool slowly. The problem is where I have used the grinder is real smooth and not like the original casting. When it is electroless nickel plated the repaired area will look different. I didn't understand the broken grinding stone on a stick approach to make it look like original. How is that actually done. thanks, Stan

T. Cotten
12-04-2006, 08:56 AM

The "Outlaw's Friend" is used like a hammer to scar the surface. After using one, you will soon learn to spot repetitive impressions upon number bosses that have been felonized. It will not embed abrasive nearly as much as the old beat-on-sandpaper trick, and gives a wider variety of irregularities.

You will not be able to add much 'character' between fins, of course, but it blends the edges and open areas nicely.

Still, the steel shot blast is the last word for texturizing, especially for aluminum.
(Attached is an example of where 'character' has been sanded off and the surface re-textured.) Blasting is the only effective way to get between fins, that I have found so far. Of course, there are much more coarse and aggressive media available.


12-04-2006, 01:18 PM
Thanks again for the rod recommendations swall.

Cotten...that tool looks to nice to use. My wife would think it was colonial furniture. ;) Nice work on the carb bowl !! Paps

08-02-2009, 06:04 PM

I'll give you a call to see if you still have fin material.

A wise person told me at Davenport a few years ago that, "All old motorcycles should be destroyed -- one mile at a time." Sound familiar? Well, I took your advice and have ridden and hauled my Indian 841 to veteran's events, a Moto Guzzi rally, and antique bike shows. Every time the bike is moved, there is potential for new dings. Even so, this has to be a better use of the bike than letting it languish in museums like it did before I got it.


David R.
08-30-2009, 07:12 AM
I have a Triumph head with two broken fins. One is missing entirely and the other is fractured, but still clinging. What is the procedure for dealing with these repairs?