while reading in a book from D. Vizard: for nitrous use he strongly advices to make the exhaust ports as big as possible. if you have a 1.94/1.5 head, u better leave the 1.94 for what it is and let a machineshop enlarge the 1.5 exhaust to 1.7. He says that 1.7 valves were used by some pontiac vblocks, so they are available. If you enlarge the intake (1.94) to 2.02 or bigger, there wont be enough room for bigger exhaust ports. due to much more exhaust fumes created by nitrous, its better to concentrate on the exhaust flow. He dyno tested a 350ci with 1.94/1.7 heads and he used a 100hp shot nitro injection and it produced a gain of 192hp! hope it helps... cya!

Thank you.

your welcome

I have that book... I always wondered what that would do N/A horsepower wise? I considered doing it to my vortecs once upon a time.

I suggest anyone who hasn't already to borrow or buy some of his books. The guy really knows his stuff.

I’ve played with porting some vortec heads and it’s not really necessary to do anything all that weird with the valve sizes to get big exhaust flow numbers. I saw 233/215cfm @.500” (about 92% e/i flow), and 238/221cfm @ .550” (almost 93%)

I’ve played with porting some vortec heads and it’s not really necessary to do anything all that weird with the valve sizes to get big exhaust flow numbers. I saw 233/215cfm @.500” (about 92% e/i flow), and 238/221cfm @ .550” (almost 93%)

WRT to NA, it shouldn’t do much, but should allow you to run a slightly smaller exhaust lobe and make the same power, so in theory you could have a milder engine with the same power output.