I pulled off my L98 aluminum heads a few months ago, to refresh them and sell them to another SoCal member for an engine with a ZZ9 cam. My dad Dyno Don had ported them as far as we could when we put the current engine in the car a few years ago. Anyway, they were cleaned up and new Manley 1.94 intake and 1.50 exhaust valves with undercut stems were installed. (part number 10721-8 and 10722-8)

They flowed 235 cfm at .500 lift on the intake, and 193 cfm at .500 lift on the exhaust, with a pipe. Only the numbers at .500 were checked as this was just a quickie flow job to see what they were, not something serious.

According to Chevy High Performance (http://www.chevyhiperformance.com/te...photo_08.html), these heads when stock flow 196 cfm at .500 on the intake, and 155 cfm at .500 on the exhaust, with a pipe. So we did see a decent gain with our porting.

The dyno and ET numbers in my sig were done using these heads with the stock straight stem valves. Its estimated the undercut stem valves are worth 5 or 6 cfm. I'm upgrading to a set of Trick Flow 195's with an SLP 224/232 camshaft.

 

Kevin.....just a heads up on the Trick Flows....I installed a new set of the 175's with the small springs last spring. Used the stock L98 cam w/ 1.6 rr's for about .460 lift. Heads good to .480. Anyhow here we are 1200 miles later installing all new springs, locks, retainers etc because the damper springs on a couple of cylinders broke. Looks like the quality of the hardware might not be up to snuff. Happy with the castings...just not happy with the valvetrain coming apart.

 

good stuff, that great improvements.
which heads are you going with? the regular head or the signiture series. i heard that they came out with a fully cnc'd head too that's suposed to be great.

hey rob, what kind of ganes did you see with your heads?

 

Happy with the performance....I've made to many changes to tell where the gains came from though. I'm sure a tune will step it up a notch over and above where its at now. Again I'm happy with the castings...but the cost savings obviously comes form the sub standard valve springs.

 

 

I purchased Allen's old heads (1989TransAmGTA). They're the regular Trick Flow 195 heads from a couple years ago. The springs have already been checked, and they have lost 5 psi from new, nothing to worry about. He put less than 10k on the engine since my dad Dyno Don installed it two years ago, so I'm not worried. They will be ported the same as these L98 heads were by Don, so I should see higher numbers than the 330/385 Allen made with them.

 

They had about 3000 miles on them. Virtually brand new.