lol i just realized it would be that far haha... how far out of the hole would be safe?

 

I would bore it .015 over and run high compression pistons if you are keeping it N/A.

 

bore it .015 over eh?

wtf LOL

 

I would shoot for 5 in the hole (0.005") piston to deck clearance. Depending on your motor, you can usually get a combustion chamber that puts you in in the 9-10 compression ratio range...assuming you dish/dome is nothing radical. You will of course want to check valve to piston clearance, but 5-10 in the hole is pretty normal I think. Some guys shoot for a flat deck 0 in the hole, but that is not really necessary in a street car.

 

I agree. What are you talking about?

 

boring the cylinder .015 over.

 

Uh, why? 1st off, why use a hard to find 255 crank? 3" stroke is the same as a 302 so that doesnt really help. 289 and boss 302 rods are the same length, so why not use a boss piston?

 

Why? Most of the time it takes at least 20 over to clean the cylinder up and most aftermarket pistons are only available in std, .030, .040, .060 and .125 over. Help me if I am missing something.

Racin66, what are you trying to build so we can help. This whole thread is getting confusing, so help us narrow down what your intent is (i.e. 289 stroker???cleaned up 289???500hp small block???).

 

the 255 crank IS a 302 crank, iIRC they even have the same 2M casting number. they aren't scarce and are nothing special.

urban is right, you cant get pistons any smaller than .020 over

and yeah, if your wanting to use cleveland heads you need to use a 302 crank with 289 or boss 302 rods and boss 302 pistons. now, maybe there are other pistons in the catalogs from chevy or dodge that would have the right compression height but you's probably be boring the small end of the rods and bushing them to make the wrist pin work - and by the time you did that you might as well have just bought the right pistons to begin with.

*edit* whats all this talk of not needing a zero decked block for street applications?!?!?!





actually its .002 in the hole, but with a 289 i needed to do everything i could to keep compression up and with the 60cc 351w heads it still like 9.0 - 9.5:1

 

who sells boss pistons? is there a part number?

i wanted to use the 255 crank because it only weighs 32 pounds compared to 38 of a different 302. i have the 289 rods. and im trying to get the heads. how much are the pistons? hyper would be ok but if forged isnt that much more its ok.

i think i could get a crank at a parts store or ebay, id be willing to wait a little while