piston size 502

[tommyb]

I could use some help in choosing the right size of piston for my engine 502 MAG MPI year 2000, my cylinder bore is 4,533 my question is which size of piston will fit in order to give me the right piston clearance ???
The engine is standard except from the bore size.

[offthefront]

depends on the Piston .... a 4.530 will only give you .003 ....contact JE ...

[C35]

That tight of bore makes me wonder if you're getting an accurate measurement. I'd take it to the best automotive machine shop I could find nearby and have them measure it. You're going to have to get it honed anyway to get final clearances right and to get the proper crosshatch for ring seating. Also, if it's been used much at all, the point miday is going to be a little larger than top or bottom because of rod ratio and side loading.

Also, the stock piston is made for GM by JE. It's not available from them directly. It has a raised dome where the JE and SRP replacements they offer are flat top. You give away I think about 3 tenths of a compression point which needs to be made up by milling the heads. You can get a little of it back plus a bit of performance by decking the block and using the proper gasket thickness to get the tightest quench clearance you can get away with. Lets you up the compressoin a little without risking detonation.

[imco offshore]

I thought a 502 bore was 4.470

[Ratickle]

I thought a 502 bore was 4.470

Actually 4.4660 in the perfect stock release from the factory

[Ratickle]

My guess is he has a .060 over 502 that is either tapered some from running, or is measured slightly wrong and is .060 over at 4.526. I guess the average from the factory was actually 4.568. And George is correct. On almost everyone's discussions the .060 over is commonly refered to as 4.530 and stock 4.470.

I guess there could be a possibility it was done purposely that way for marine clearances and is designed to use a standard .060 over 502 piston.

I've been told that .005 clearance on performance street and add .001 or .0015 to that for performance marine. But, there are a lot more guys on here who know what is correct. I'm just repeating.....


Anyway, his final should be a 515 cu in engine?

[MILD THUNDER]

My

Anyway, his final should be a 515 cu in engine?

Yup, as long as he's using a 4.00 stroke crank.

[Donskihp]

If you haven't done it I would recomend having all the cylinders maped so you know what you have. Cylinders have a tendency to wear out of round and not straight up and down, and if you just hone, that may not correct any distortions

[Bilgerat]

I have a couple sets of standard bore JE blower pistons if anyone has a use for them. Brand new.