Finally flowed a 91-95 head

[SappySE107]

My numbers a different than the others I have seen on here. Exhaust side especially. I think its because I used a tube off the head instead of letting it create turbulence right out of the port and kill itself. Its the same method I use for the pushrod heads so you can compare all of my numbers on the site (not all the forum posts cause I posted some when I was learning how to setup the heads). Anyway, here you go. Ill post the 96 exhaust port once I flow it.

Stock Intake
.050 51.6
.100 101.2
.150 150.1
.200 190.1
.250 220.1
.300 245.9
.350 265.7
.400 277.6

Stock Exhaust
.050 52.2
.100 99.5
.150 137.7
.200 163.7
.250 183.7
.300 195.9
.350 203.2
.400 210.0

[Sourmug]

Bear with me as I have no experience reading flow bench data.

It would seem to me that the exhaust ports present a substantial restriction when compared to the intakes, correct? If this is the case, is the restriction at the valves or withing the ports themselves? What would you recommend to improve the flow?

Thanks
Nolan

[SappySE107]

Exhaust valves are smaller in just about every engine out there. There are ratios (about 85% flow for the exhaust) that are ideal for certain setups but then again, no one can give me a formula or reason for x% being better under y condition.

Stock is 86% exhaust flow compared to intake, which is pretty good.

[lkurek]

I have ported and built many a set of heads for street cars to sub 7 second cars

Those flow numbers are quite impressive, and yet typical, for a 4valve head. A stock LT1 aluminum head intake part flows about 200cfm stock, so you can see how the duals really kick it up a notch.

As for intake/exhaust ratio....80-85% for a NA motor is about perfect, while a supercharged motor can go 85-90%. Remember, when you are clearing the chamber, you have a high pressure situation that helps flow the exhaust out...while the intake uses atmospheric pressure (14.7psi) alone. You want a good balance, as too much flow out the exhaust can affect scavenging and tuning....you don't want to pull fresh charge out the exhaust during overlap!

I'd be curious to see the 96-97 heads...as I have a few sets I'm getting ready to work with.