I found a 2.8, 3.1 and 3.4 cylinder head flow chart.
The intakes flow about 117 cfm @ 28'' of H2O between .350'' and .400'' inches of lift in stock form and the way the #'s look I don't think they flow much more than that even out to .525''.
Heavly porting them yeads about 130cfm at .450'' with the same water.
There ported version gives 130 intake and 131 exhaust flow with the same water and .450'' lift.
It has to be that 1.73'' intake valve.
I will try and cut the intake runner taller and making the ports even bigger than I all ready have (I went about .010'' bigger than stock).
There just to small being only 85cc's. They need to be hoged out severaly.
On those heads I don't know if they unshrouded the valves by porting the combustion chambe for a 3.62'' bore (3.4L) like I did.
It didn't say any theing about the combustion chamber when I read it.
I don't think these heads I have over here are going to make the cut off for the time I need to get the capibilty to install bigger valves.

 

Okay quite a bit newbish but I don't see any otherway I'ma learn.

Just for learning purposes, can you describe everything you meant by that post? like whats a cfm and how do the variables you listed affect your car? From the decimals to the cfms and where or what part they come from and what these variables are determined by. Why was water used?

Thanks in advanced...

 

A CFM is 1 cubic foot of air. I could use fractions but I have the numbes in desicamls.
28 inchs of water is a mamometer reading of how much the pressure can verticaly move the water in a tube aginst the force of gravity.
The numbers I have came from mesurement taken on a mechanical test flow bench trying to such air through the intake and exhaust ports, it is a standard way to gauge cylinder head preformance.
The lift is how much the intake or exhaust valve is held open during the flow test.
The rough stock casting doesn't flow air that well and when you smooth and open the ports you can make a lot more air flow through the port.
I also removed cast iron inside the combustion chamber so when the valves open more air can flow around them and enter or exit the cylinder easier.
I need bigger valves because the stock valves size is holding back the air flow.
With my cam and valve train my max valve lift will be .525'' (.125'' over stock).
When GM made these heads there test flow bench must have been broken.

 

Its not the valves. Its just the casting of the heads is the problem. The shape of the ports is the biggest problem. If you look at flow numbers for a gen 2 aluminum head you will see that the intake port flows just as much if not more then a ported iron head. The alum have canted valves which help to unshroud the valves which really aids flow.

Installing larger valves will just cause more shrouding and prob less flow or not enough to make a significant increase in flow.

You need to ditch the iron heads and go aluminum if you can.

Or just hog out your iron ones as much as you can, install a higher lift cam and if its a 2.8 then you can expect about 170 hp or so tops with the stock intake runner setup. a 3.4 would prob get you around 180 tops with full head work.

What will really help is a 5 angle valve job, undercut valve stems and lots of bowl work. Thats where big gains come from. Making the ports larger only slows down velocity at lower rpm so you will actually flow less air at lower rpm.

 

hit it right on the head