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Rex
01-01-2007, 05:56 PM
1. What's the correct stone grit number for honing wrist pin bushings?

2. Should I use cast iron or Ampco 45 bronze valve guides?

3. Can anyone help me with advice on honing the wrist pin bushings and valve guides?

T. Cotten
01-01-2007, 07:44 PM
Rex!l

If you are useing a positive-stone hone (such as a Sunnen), then please follow the manufacturer's recommendations as outlined in their catalogs, as numbering systems do not always jive.
Normally a plateau 'mill-profile' is desired by utilizing a couple of progressively finer grits until finished with an ALOX-impregnated nylon brush, resulting in varied depths of cross-hatch but with no burring.

Ampco45 guides would suggest that you are considering serious competition with frequent tear-downs,...Are you a racer!?!

Besides Sunnen, there are other fine manufacturers of positive-stone hones: Peterson and Delapena come to mind.
If you are not already outfitted, then a visit to your local automachine shop would be most practical for you.


...Cotten

Jack_Hester
01-01-2007, 07:47 PM
Rex -

I ream wristpin bushings. I'm sure there's a method to hone/lap non-ferrous metals. Reaming with an adjustable parallel-bar reamer gets them mighty true.

I use cast iron valve guides, for long life, and ream them with a stepped reamer. I have many sizes, so I measure the valve stem, add the clearance, and pick the appropriate sized reamer to do the job. Then, I re-cut the valve seats, using a tapered pilot (several sizes of those, too) that fits the newly reamed guide.

Jack

Rex
01-01-2007, 10:04 PM
Cotten and Jack-

Thanks for the quick replies.
I don't have any honing or reaming tools, don't know what to ask for, or where to look. I'm only attempting to do this myself since this motor's already been to two pro shops without positive results.
Is all this honing and reaming done by hand, or are jigs and fixtures required?
I found the valve guide clearances to be between .0067 and .0095, and my manuals indicate they should be .0035 to .0055.
Wrist pin clearances were .0002 and .0003, manuals showing .001.
I don't intend to do any racing, just highway speeds. I only asked about the Ampco guides since I'm not familiar with any of this, but did see it in the catalogs.

charlie frey
01-02-2007, 02:46 PM
I'vebeen getting by with an adjustable reamer for wristpin bushings (go slow...I have one that reminds me of my impatience when it warms up and taps), and a couple expansion reamers for guides.

T. Cotten
01-02-2007, 08:46 PM
Wristpin bushings for vintage machines are nearly always supplied with an I.D. that requires undersize reaming before a hone can be applied anyway. But upon honing, the chatter and "rifle-ing" of even a solid reamer cut soon becomes evident.

Honing allows for a precise fit to wristpin variances, give or take a couple of tenths of a thou...
This assures a longer life for the bushing by virtue of a more complete bearing surface, as well as a proper cross-hatch to distribute oil.

Beware that any wristpin bushing replacement is not likely to be perfectly aligned or concentric with the last.
Thus, all rebuilt rods should be straightened and aligned . Any straightening of a rod while installed will be a compromise, and even a risk if performed upon the female rod.

Good luck is needed if this shortcut is chosen... Very good luck.

.....Cotten

Jack_Hester
01-03-2007, 05:47 PM
Cotten is right about straightening a rod after it's installed. I know that there are untold numbers of manuals out there with photos of the procedure showing this method of straightening. Makes my skin crawl. Can't bear the thought of applying this pressure to fresh rod rollers and races, either. Just me. This method of straightening is the reason why old rods need to be checked, out of the machine. They are almost always 'man-bent' at some time after they leave the factory. Once a new bushing is installed, the misalignment becomes obvious to the builder, if it is checked before assembly.

Jack

Rex
01-03-2007, 07:36 PM
After much research, tool shopping, and reading of your collective advice, I've decided that it's not in my best interest to persue the reaming and boring myself.
I did aquire the following tools in the course of this research

0-1" Mitutoyo micrometer
.125"-.500" Mitutoyo small hole gage set
5/16"-6" Mitutoyo telescoping gage set
2"-3" Mitutoyo micrometer

I did use these tools to determine which parts need to be modified or replaced, and I know they will serve me well in the future for other uses.

I also found an engine builder within driving distance who is equipped for and familiar with what needs to be done. He's got extensive experience with flathead motors and is aware of their unique clearances. I visited him at his shop today, and got all my questions answered.

And another thing - I intend to use fiber head gaskets, which I'm told should be coated with silver paint. Are they to be installed with the paint wet, tacky, or dry? Paint the gaskets only, or the head and cylinder surfaces also?

charlie frey
01-03-2007, 07:53 PM
The only time I've used silver paint is when running no gaskets at all.
Those fiber ones are so thick...I bet they'd fill in gaps up to .006 or .007".
No need for paint.
Why not use copper?

Rex
01-03-2007, 08:33 PM
I was advised to use copper with iron heads and fiber with aluminum. My heads are #6 aluminum. Maybe subconciously I'm drawn to a non electrolytic material sandwich with the fiber between the Fe and Al. Although the heat conduction aspect of the copper is attractive. Copperfiber!

Paps
01-03-2007, 09:37 PM
Rex......did you also obtain standards with those micrometers ? You need a known certified standard size for calibrating them for accuracy. Paps

Rex
01-03-2007, 09:54 PM
2"-3" yes. 0-1" is on the way.