so if i have a 76 350 which has a dish piston and 76 cc heads, i could get more compression by going to a flat top, or even a .125 dome and not have problems seeing that the cc of the head is so big right? id like to get it up close to 10-1. i know i would be better off finding better heads too in the future but this is one step at a time.
Sure domes will do it, you just need all the particulars like actual chamber cc, deck height, gasket thickness and cam timing to figure out the compression ratio and what your valve-to-piston clearance will be. Devon
thanks devon. the motor in my dads chevelle started to knock at the end of summer, and instead of fixing the 2 bolt main block im ordering him a marshalle blue print short block and swapping everything over. thats why i was trying to figure our if i wanted to order the one with flat tops, or .125. i may actually go with the flat tops because he mostly just cruises and i found that the flat tops with those head are approx 8.42 to 1 compard to 9.47 to 1 with the domes. i know he wants to run it on the cheap stuff with gas prices climbing. the car ran 13.52 with the dished pistons that are in it so i know hes not going to go any slower the 2 times a year he goes to norwalk with his buddys.
You can buy flat tops with a higher compression height than stock. Notches are usually there (and should be checked for clearance) and will work unless you have some specialty heads where valve angles/location require particular pistons with the appropriate notches. Before doing so you must know if they will work with the combo as the block may have been decked already. The sbc has many piston options. Ray
Flat tops with a 76cc head will get you 8.8 static ratio. Most of the small block flat tops have 5cc valve reliefs. Mine do, and they're .017" in the hole with no decking on the block so that's about standard for a 350. I've got 64cc heads with these pistons and ended up with a 10.2 static ratio and 9.2 dynamicratio with my cam. Timing is set at 36 total without the vacuum advance and I have no detonation problems whatsoever. If you can, pick up a set of `70 or older heads for it with 64cc chambers. There are tons of good aftermarket heads available for them but for stock replacements #186's are great heads and can still be had fairly cheap. A #462 will be the same head but won't have the accessory bolt holes in the ends. There are other choices but these are the most plentiful. Try to stay away from domed pistons if you can, they distrupt the flame travel across the piston.
My olld 355 used to have the 74?cc heads. There was only 2 casting numbers in 69 very rare that had that cc, and i was lucky enough to have a set lol. I had 11:1 TRW's in there, a 284H cam, 4bolt main, 1.95, 1.5 valves, and stock rockers. The TRW's had notches in them, but i could have gone to a 1.6 rocker and still had no issue. The actual compression was just a hair over 9:1. It was a good combo, depending on how I tuned it, i could set it up for street driving with crappy 87 octane fuel, or advance the timing quite a bit and run 94+booster octane gas for the track. In its hay day the engine was good for about 350hp, but It was down to 250 when i was done with it. So you should be able to go flat tops or even dome with no issues, it'll take alot to get it anywhere near 10:1. If youre rebuilding it anyway, you will know exactly what your putting in, so its easy enough to measure.
