Dean Eechaute

I am rebuilding a 66 425 motor and am having problems finding pistons. Anybody know a source for these and what compression ratios are available? I have also heard about using 455 pistons with big block chevy rods and machining the connecting rod journals to get the 4.25 stroke on the forged crank. Has anyone done this? How did it work and how much did it cost? Thanks, Dean

Oldsmaniac

If you need stock type cast pistons EGGE has them new and in stock. Other than a race engine cast pistons are fine for a street car.

Dean Eechaute

I agree the cast pistons would work. I looked at the site and could not find anything below a 10.25 compression piston. Too much for cast iron heads on pump gas and questionable on aluminum heads. Thanks, Dean

Dean Eechaute

What would be the difference between the pistons in a 425 as to the 455? My guess would be the location of the piston pin. Would it be a better solution to use low compression 455 pistons with custom connecting rods? Dean

Oldsmaniac

I found these on EGGE
L2213
OLDS 425 C.I. 1965-1967 9:1 Compression Bore 4.125-4.185

Dean Eechaute

Their on line catalog only shows L2214 which is the high compression stuff. I sent them an email to clarify this. Thanks, Dean

bigD

kanter offer a low & high compression cast piston... you can find them on ebay thru falcon global or buy them from kanter. my local machinst has used them and speaks highly of them...

coppercutlass

with a thicker gasket like .040 i think the compression would be lower than 10.25 to 1 . The o.e. gaskets where between shim gaskets .018 and .022 also find out the deck hight and how far in the cylinder the pistons sit. i think you would be fine running the 10.25 to 1 pistons with an .040 felpro head gasket. I think realisticly you will be under 10 to 1 again depending how far the pistons are in the cylinders head cc's and piston dish cc.

69 Ragtop

Here are some Sealed Power (SpeedPro) pistons at Summit:

http://www.summitracing.com/search/D...?Ns=Rank%7cAsc

Interestingly, the forged ones ($53.99) are cheaper than the cast ones, but all are much more expensive than the 350 Olds cast pistons (about $27)

coppercutlass

Those are for a 455 the pin height is diffrent from the 425 same bore diffrent pin height.

69 Ragtop

Oops. Sorry. I should read more carefully.

Rickman48

Dean - shorter rods give a undesirable load on the cylinder walls - longer rods are always better in long stroke motors!