If pistons could talk....with pix

[tbirdtbird]

Model A Pistons.jpg Pictured on the left is an old school Model A piston with an archaic design from the '20s, '30s, '40s.
On the right is a Model A piston of modern design, a design adapted by all car manufacturers many decades ago. The skirt is short and the rings narrow. Inspect the features of the two yourself; you need not be an engineer. You only need common sense to answer the following 3 questions:

1. Which piston would have the least friction, and thus the least parasitic drag, and heat?
2. Why would the car companies have made the switch?
3. Which piston would you prefer in YOUR car?

There is only one choice I use for the engines I build. I use the same clearances I and others have been advising right along, because of the very uneven and inconsistent cooling of the Model A block bores.

Whenever you see a clearance spec from a manufacturer which states .002-.0025, know that is a clearance for a modern car. Engine builders everywhere should recognize this immediately. Modern cars have vastly improved water jackets, cooling systems, and alloys that are quite different from those of yesteryear.

One of the two designs is gonna let you down on a long tour. In 1930, people did not tour mile after mile; they had to work! There were very few roads you could tour on anyway.

Information that is printed on a piece of paper needs to be reconciled by comparing to hands-on people's real world experience. The two do not always jive.

[Mitch]

Dave is that the Egge custom piston you get made?

[tbirdtbird]

Yes and no.
I get them from John Cosper in NM. He has retired from engine building, but still has Egge custom make these pistons. Custom made, because although the bore of a 283 Chevy is identical to the bore of an A, the pin is in the wrong place. Egge custom makes the 283 style piston with the pin in the correct place so you can use your stock rods. Very nice pistons, a dream to hold them in your hand.
I know George Miller and others have used them.
There may be other sources other than John.

I'll ask the question a different way.....would you put old school long skirt wide ring pistons in your modern Ford, Chevy, or Toyota?

[George Miller]

No I would not use wide ring pistons. pistons that have skirts that are not oval. The modern pistons are the way to go. The big problem is the A engine has the piston pin off set in the block. Modern cars have the off set for the wrist pin in the piston. So you will end up with to much offset.

[BILL WILLIAMSON]

Who's Cosper?
Bill W.

[George Miller]

the 283 pistons are not perfect for the model A, but they are better than the new ones made to replace the original pistons. The rings seat better also because of the narrow design. Could the 283 piston be improved for the A yes.

As A side note I won a few hill climbs using 283 pistons. I will keep using them in my engine until some thing better comes along.

[DaWizard]

Since I can't remember the last time I purchased a set of pistons, nor rebuilt an engine, please humor me and tell me why, IF the 283 pistons are the same diameter, obviously not the same skirting, and the wrist pin is the same, exactly what needs to be changed to make them fit?

[tbirdtbird]

The stock Chevy 283 pistons have the pin in the wrong place, and the wrong diameter. The custom Egge pistons have all this corrected, so that stock A rods can be used. So the two cars, as stock, share the same bore, but not the same anything else

[DaWizard]

So, you are saying that if the wrist pin remains the same, it will change the stroke and not work? What, how much is the difference, if you know? Also, if it is lower and would pop up the piston too high out of the block, why not just fly-cut the head a few thous?

[tbirdtbird]

The stroke won't change but the piston will be in the wrong place. I once knew how far off the 2 pin bores are, but have long since forgotten. It is significant, tho. Recall also the 283 pins are smaller diam.
Getting the right piston is just so easy......slap on your existing rods, assemble after checking clearances and gaps, and off you go. I am sure Geo Miller knows the pin bore differences

[George Miller]

Not sure of the wrist pin size. It was something like .891. It has been a while and I'm getting older. They are smaller and in the wrong place. What I did before I found out about Egge pistons was make new rods to fit the pistons.

[Greynomad]

I've often wondered why the vendors do't sell the modern style pistons. Anyone know? Maybe they think too many people wouldn't buy them because they are different.