You'd have better luck posting your question here:I have a question to the general membership--I am about to install a set of gt40p heads into my 1948 ford panel truck that has a 70,s 302 in it. NO Smog setup in canada due to the age. All I am looking for is a little more pep because the truck weigh's in at 4700 lbs. The engine is a stock 4 bbl, I will be adding a new exhaust system with the proper Mac headers just wondering if I should rest the timing back a bit and if so what type of hp increase might I gain..Thanks Butch in Ontario Canada.
5.0/5.8 Engine Tech