I'm doing a performance build on my 72 350 in the near future. It will not see much street use, but I will be swapping in a th400 with a switch pitch convertor. My question is ( with heads and block untouched, at least that's what previous owner said) I would like to run at leats 10.5 or 11 compression ratio with custom pistons from TA and 1.92 intake and 1.55 exhaust . Will these pistons need to be notched for valve clearance, and will I be able to achieve 11:1 with 72 heads? I like to know cc's for 72 heads as well. Any Advice is appreciated. The engine will get thorough rebilud, oil pump, cam bearings, crank bearings, etc.
Theres not a whole lot of difference in the 350 heads as far as combustion chamber volume goes. My block was decked .050 for a deck clearance of.005 and my heads were milled .030 I have the the big stainless valves from TA also. The cam, pistons, heads being milled or the block decked is going to be a factor, I have TA's 310 in mine and Sterling pistons w/ valve notches. I checked the clearance and all was good, BUT each combo is different, double check yours Also use the TH 350 trans, it eats less horsepower than the TH400, the 400 is not needed for the small block, its kinda over kill:TU: Hopes this helps, Mark
I was planning on using TA 310 cam as well, what compression are you running? Thanks for the advice on the transmission, what stall speed do you run, I'm guessing not too far off from stock as the long stroke on these engines tends to put the torqe lower in the rpm band.
Hey bubarge! The Sterling pistons Im running say the comp ratio is "suppose" to be 9.2 to 1 at .020 deck height. But Im at .005 deck height and my heads have been milled .030, sooo Im guessing Im at a conservative 9.8 to 1 maybe higher. The piston part number if I remember correctly is H522NP, the have a very small dish in the center about the size of a quarter, and 4 valve reliefs. I smoothed all notches in the pistons and lightly polished the combustion chambers in the heads before I reinstalled the big TA stainless valves (heads were ported, bowls and ports opened up a few years ago) I have no problems with detonation using 92 or higher octane gas. My convertor is a TCI which is suppose to stall 1000 higher than stock, its probably around 2500/2700 stall. My idle vacuum is 10" Rear gearing is 3.42, I actually wanted a 3.23 set, but Richmond doesnt offer that gear with the 12 bolt. True these engines make killer low end torque, but low idle vacuum from the TA 310 cam WILL stall the engine with the tight factory convertor, even with the the higher compression, ALSO TA says at least 9.5 to 1 comp with the 310 cam. The 310 cam is great with the rite build up, its pulls like snot to 6000 rpm and I can smoke 'em from a 10 mph roll thru first and second gear, but it does tend to drift sideways doin it tho:beer Hope this helps yah, Mark
I don't know about the sterling pistons but I have the forged 30over JE pistons and they are .035 down the hole. My compression is 10.1 to 1 and don't have notched pistons. If the plugs where at closer to deck my comp. would be closer to 11 to 1. Your stall will depend on your rear gears. I would go with a min. 2800 stall and probably 3000 would be first choice. TA should be able to recomend the right stall for your set up though. The heads you have should be right around 55cc. chambers. Thats what mine turned out to be with .005 taken off of them.
Stall speed has nothing to do with rear gear ratio. The rear wheels are not even suppose to be moving yet when your approaching stall speed.ou: Mark
Mark that just isn't true. I have a 2500 stall converter in my car. the rear wheels will break loose at 1500 to 1700 easily and I have 273's. The stall speed is where the converter is fully locked up. Not where the tranny starts to get power from the engine.:Smarty: The stock stall converter is totally stalled by 13 to 1500 rpm. That's why you can step on the gas and move the car from a 500 rpm idle. If the stall converter kept you from moving until it was almost at its stall rating you wouldn't be able to start moving your vehicle until then. Engine torque has more to do with converter stall sellection than rear end gearing, but rear end gears has a role as well. If you have 410's the reaction of the transmission is much faster than if you have 273's. It's all a matter of torque.
