spinish

hay I have a stock 350 with stock dished pistons.i was wondering how to get 10 to 1 compression wih out changing pistons. o ya i have 64 cc heads. any comments would healp. thanks

anthony714

cant be done w/o knowing 1,amount of "dish"your stock pistons have,2,you need to know your head gasket thickness,3, youll need to know the deck height or the distance from the top of the block the pistons stops at,youd think it was at top top but no stock engine would be at a "zero deck"..and finally 4,you need to know your head cc..,yes i know you said 64s,but those are "rough" ccs by head maker.those can vary a few ccs either way and if the head had a valve job,is the valve sunk more and now you have a larger cc head????to get a true compression ratio youll need to know all that,and then you can get a true 10-1,other wise the rest is a rough estimate and can vary ,you might think your 10-1 but actuall 9.2-1.........besides why do you want 10-1 verses stock?find other ways to make power.going from a stock ratio of about lows 9s to 10-1 aitn going to make a whole heck of a difference.i also think the small cc head i seen for a sbc is 58cc,you can mill it but never mill unless you have to....

spinish

he reason for 10 to 1 is the cam i have is a comp xe268h. and i was told by a couple of people that i need 10 to 1. right now my cranking presure is 170. i thought that was enough for my cam. what do you think? My deck height is stock 9.025''.gasket is .020" dish is i think -10cc

anthony714

maybe i explained deck height wrong,yes your deck height might be what you list but you need to know how far or how close to the top of the cylinder does the piston come.a piston in most engines will not come to the actuall top of the block,therefore theres extra space so to speak inside and it lowers your actuall compresion

anthony714

i did some quick math knowing what i do and your figures,also leaving out deeck height.but i think your stock ratio around 9.2(theretically),using a 64cc like you have and going to a 58 cc head will raise cc roughly 3/4 of a point or .72..thereby giving you a "theretical" ration of around 9.92....close enough to 10?

spinish

thanks. I was just wondering what you can do with a stock bottom end. not what i have. I was looking for someone who have taken a stock 350 with 10 cc dish and got around 10 to 1. like decking to zero .020" gasket mill the heads.030" like that for an example. leaving the pistons alone. because i can get free machine work but not parts.

anthony714

you cant zero deck w/o tear motor apart and machinng block

spinish

Ya i know

84firebird

first things first, compression will help pick up a lot of horsepower from like 8.0 -9.5 but from 9.2-10 aint gonna pick up nearly as much, and it will heat up faster too...

main issue i hear is going to 58cc on the heads.... bad idea in a 350, (sidenote the 305 heads were 58cc), and issues arise with small chambers.... as in your valves (possibly shrouded also) hit your pistons, especially with only .020 gaskets, however if you wanna squeeze more compression, you can also go to .015 gaskets, and get your block decked accordingly, cheapest way, probably most efficient and you have the least worries, i think .016" is 'stock' (top of piston to top of block), but my machinist decked mine to .017" from around .024"

now static compression is one thing, but you also might want to look for a dynamic compression ratio calculator (they call em dynamic, it's really geometric, but who cares) but that'll tell you how much compression you have from the intake valve closing point, which if I'm not mistaken, you dont want more than like 8.5-1 dynamic for running on 93.... just something to look at.

otherwise get some new pistons, ebay has em cheap, otherwise summit, and you dont have to sacrifice your heads. If i remember correctly the standard price for pressing pistons onto your rods (containing stock pistons) is $7-8 a pop so $56-$64 + whatever your pistons cost.

just some thoughts, good luck

spinish

thanks alot you gave me some things to to think about.