Originally Posted by shortdog
bought old 70 chevy, heads shot, believe its a 255hp 9:1 350. plan is to make a daily driver out of it.... have a fresh set of tbi 193s with a aluminum gm intake and 600 carb to boot on stand by.... truck has 3.08s and I have a 700r4 as well. switching to the 65.3 cc will add CR but will it still run on pump gas? budget on this one is much less than shoestring... have enough for head gasket kit... and if it will work what head gasket ( thickness ) should i use.
Having the casting numbers of the old head would help in figuring out if you're headed for compression trouble or not.
For a carbed daily driver where top end horsepower to race Beemers isn't desired, the 193 Swirl Port makes for a decent head. They pull very well into the 4000 RPM range before they just can't feed the 350 any more mixture. They get pretty decent mileage at cruise due to the spin the ramps put on the incoming mixture through the intake valves. These heads have some of the desireable features of double squish/quench and the spark plug moved inboard toward the valves. These features and the high intake swirl make them tolerant of more compression without detonation. Still one neededs to be careful and not let the SCR get much beyond about 9 to 1. You don't want to compomise on detonation by brining timing advance down as the power and mileage loss quickly becomes significant.