piston choice problem

67rcks · May 16, 2008

Are there any OEM-like replacement pistons available for early windsors? Anywhere I look I see e.g. type of pistons as attached. recommended for 302s
(available from summitracing - speed pro)

This one has about 3/4" shorter walls than OEM piston (also shown on picture). Also it has only 1 oil hole to lubricate piston pin, OEM has one additional, about 3/16 hole opposite to this one. The non-friction parts are not machined, just whatever comes out from the cast form.

It is my understanding that longer the piston, the better it sits in cylinder and less likely it causes cylinder wall wear or get stuck. Is it safe to bet on these shotr-wall pistons e.g. speed pro ZH273CP? Is it a good idea to drill another opening for oil, as it is on the stock piston?

D.Hearne · May 16, 2008

Short pistons usually go with longer rods. The piston application you're looking for is a 69 351W 4 bbl, this is the 10.5 to 1 flat top piston. If you want lower compression, look for replacements for a 69-71 351W 2 bbl. Silvolite # 1144 is the 69-71 flat top replacement.

rbohm · May 16, 2008

i have a set of 351w replacement pistons. they are std bore though, so if you need .030 over i cant help.

Fast63 · May 17, 2008

67rcks said:
Is it safe to bet on these shotr-wall pistons e.g. speed pro ZH273CP? Is it a good idea to drill another opening for oil, as it is on the stock piston?

First of all, if those pistons were so bad, they would not sell, and would not even be listed.

Secondly, why would you destroy the piston by drilling holes in it? If the hole needed to be there, the piston manufacturer would put it there. By drilling a new hole for what YOU think would be better oiling, you could actually compromise the oiling system and then truly destroy your pistons.

67rcks · May 18, 2008

D.Hearne said:
Short pistons usually go with longer rods. The piston application you're looking for is a 69 351W 4 bbl, this is the 10.5 to 1 flat top piston. If you want lower compression, look for replacements for a 69-71 351W 2 bbl. Silvolite # 1144 is the 69-71 flat top replacement.

I have a tall '73 block and 2bbl heads, with big big chambers, so I want to increase compression with a flatter pistons. Summit tech recommends this piston with any 302w and I guess 351w too. And I want to use these pistons but wanted to make sure before their installation they are not junk and will not cause premature wear of cylinder walls due to being shorter than OEM

D.Hearne · May 18, 2008

The only time you can use 302 pistons in a 351W block is with a stroker crank. I don't recall which one it is (but I'm sure someone else will chime in with the info) it could be the 3.85" stroke cranks which I think uses the stock Windsor rods between the 302 pistons and the crank. The 73 block isn't that much taller. The difference is only .020 and that can easily be removed with a deck milling, something that might need be done anyway to true up the decks.

67rcks · May 19, 2008

D.Hearne said:
The only time you can use 302 pistons in a 351W block is with a stroker crank. I don't recall which one it is (but I'm sure someone else will chime in with the info) it could be the 3.85" stroke cranks which I think uses the stock Windsor rods between the 302 pistons and the crank. The 73 block isn't that much taller. The difference is only .020 and that can easily be removed with a deck milling, something that might need be done anyway to true up the decks.

What I was talking about is the piston itself, not its application (anyway 302 pistons do not work in non-stroker 351 at all?) What I was looking for is some logical explanation why aftermarket companies make these pistons with shorter walls than OEM, and if it causes faster cylinder wall wear.

D.Hearne · May 19, 2008

Shorter skirt pistons are uaually aimed at the race only applications. No sense using em in a daily driver application, they will wear faster. Shorter, lighter pistons help in the HP production by lowering the rotational mass.

piston choice problem

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