pistons for 302w
- Thread starter pazur
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SoCalCruising
Founding Member
Almost. No Boss 302 pistons, please. So long as you have 5.090" rods and an 8.2" deck block, they should all work. BUT, the best fit among the slight variations will be the one that gives YOUR shortblock the best piston-to-deck height. If your block has not previously been decked, then you have more choices. You may choose to buy a set of pistons, then mock up the shortblock, measure piston-to-deck, and then have the block decked to give you your desired p-t-d height (I like .005", nominal)
you could use the boss 302 pistons with cleveland heads and the appropriate sized rods (289 length IIRC)
all 289/302/5.0 pistons except the boss 302 pistons interchange. they all have the same pin height. they also have four valve reliefs, but not for four valve engines. they have four valve reliefs so they can be used in either bank. some flattop pistons have have a slight dish in them to lower the compression ratio about 1/2 a point. there are a few factory pistons that have no valve reliefs, so be aware of that fact when buying replacement pistons.
Edster
Founding Member
There was an article in a magazine about putting the pistons in backwards due to the off set pin. It seemed to give a little more power. I think it was a Joe Sherman build. The claimed dyno results were 400hp with a Victor Jr intake. w/ the RPM intake it was around 385. This was all on pump gas. Just food for thought.
that's an old, old, old trick. mopar racers used to do that back in the 70's. my first motor i ever built i accidentally installed the pistons backwards on the rods and i'dhave to say that i agree that it probably did make more power, i don't have any dyno numbers to back it up though
All 302 flat tops are not the same pin height. This measurement varies from 1.585 to 1.619. Combine a mid 70's tall deck 302 block (8.226 vs the others with 8.206) and flat tops with a 1.585 pin and you still end up with a extra 9.5 ccs added to the volume. That will lower the com ratio by 8 or 9 tenths of a point. In an 8.226 deck block with a 64 cc chamber, that's going from 8.5 to 1 down to 8.12 to 1 . Mill the deck .020, choose 1.615 pistons and you're up to 9 to 1 with 64 cc heads. Go with 58 cc heads and it'll go up to 9.65 to 1. With 54 cc heads, that puts it at an even 10 to 1.
SoCalCruising
Founding Member
Would milled, shorter block (-0.020") require shorter pushrods or milling of valves too?
PUNISHER RACING
Active Member
302/5.090, 289/5.155 rod length they both use 1.600 comp height pistons but one has a 3.00 stroke the other a 2.87
PUNISHER RACING
Active Member
Correct! The boss 302 used a different piston. It had a 3.00 stroke crank along with a longer 5.155 rod. If used with normal 302 1.600 p/h pistons you would of had your slugs coming .130 out the top of the block, with a 8.2 block.
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