Here is a link to a Popular Hot Rodding dyno test from their March 2000 mag. It covers various gm performance heads. Worth a look for the dyno numbers for sure.

http://www.findarticles.com/cf_0/m0B...41/print.jhtml

 

Well, that just pretty much verifies what we already knew. The L98 heads are decent. The Vortec heads are better for flow and power, and when machined/ported into Fastburns, they are even better. Odd how the Fastburns had to use 1.6:1 rockers to make any substantial power over the Vortecs, isn't it?

My summary on this would be that the Vortec heads (based on the LT1 heads) with improved valves and some porting treatment, the requisite stud replacement, and guide clearance, will make very respectable power. If you are as concerned over using aluminum heads on the street as I am, the iron Vortecs (or iron LT1 take-offs - if you can find them) may be the most cost effective way to go for power.

The Pro Action Iron Lightning heads are getting close, however, and will way outflow the Vortec - if you need that much flow and can handle the lower port velocities.

 

What I get out of the article is if you are going to use a somewhat high lift cam like 525-575 then the larger runners of the Fastburns would be the way to go. Also if going with a 383 or 406 they would be the better heads. Anyway 432 hp out of 350 is not too bad. I am sure if tested on a larger displacement engine the Fastburns would have shined.