Stumbled across a set of stock ZZ-4 heads, part # 12556463, 1.94" intake, 1.50" exhaust, 58cc chamber aluminum heads, screw in studs and stock springs from the zz4.

Did a couple searches on them and they appear to be a bolt-on for my 89 IROC 250/700R4 TPI.

Can anyone confirm that they are/are not a direct bolt on for my engine?

Would the stock springs hold up for the cam I have if I also switched to the self aligning Crane 1.6 RR's?

TPIS ZZ9 cam (lift .520 ex/.484 in-- dur. 282 ex/270 in)

THANKS for any advice and info.
Craig

 

They aren't a direct bolt-on since the center two intake manifold bolt holes are are 90 degrees, and they don't have the exhaust cross-over passage.

I'd get better springs.

 

You need an "old style" TPI intake to make it a TRUE bolt on...

85-86 TPI intake or find a Vette ( alum head L98 ) TPI intake, although there are some differences, it will work.

Easiest thing is to modify the bolt holes in your exisiting intake.....if you're hesitant about doing it, any DECENT machine shop will do it.


Look up the specs of the ZZ4 cam, the springs will of course handle at least that much...


HTH

 

Crap--the heads got sold!

Anyway--THANKS FOR THE REPLIES AND THE INFO--I REALLY APPREACIATE IT!!!

Some one educate me.

I assume from the responses that the ZZ-4 heads were from an earlier time period than the L98? (Sorry--guess I'm not up on my thirdgen history like I should be)

Would the L98 58CC alum heads be a direct bolt? What is the part # for those?

If, by the time U bought a set of the L98 heads --had all the work done (valve job--port/polish/CC--springs--Etc) it sounds like U would spend 1000.00/1200.00--wouldn't U be better off just getting a set of AFR's for a few hundred more, with all the same work?

The AFR's would be a better performance #'s/flow ETC--right?

 

Sorry, somehow this one dropped off my radar screen.

The ZZ4 used the Vette L98 aluminum heads, actually. See http://www.sdpc2000.com/catalog/3129...inder-Head.htm (ignore the photo) and http://www.gmgoodwrench.com/perfpart...f/24502609.pdf , page 2 - same p/n you quoted.

You can get a brand new pair for around $1000. Whether they would be money better spent than AFRs or Fastburns is a personal decision. They probably don't have as much power potential as those AFRs, true.

If you followed the post about the Goodwrench 350 engine and the linked magazine article, you'll note that they put those heads on one of those engines and gained power over the ported stock heads. However, applying the same porting work on the aluminum heads didn't produce as much gain. More extensive porting is required to produce improvement.

 

What 5.7 said. I have Aluminum L98 heads (actually ZZ3). YES, they will make power but they require more porting than just "pocket porting". Opening up the intakes to a Felpro 1204 (180+cc) over the stock 165cc makes great gains.

Where the Aluminum L98 heads are weakest is on the intake side. The exhaust side is VERY GOOD and only a little pocket porting and clean up is needed.

But, to pay $1,000 for a new set is not a good deal. I'd spring the little extra cash more for AFRs or TF 23*. Look around on e-Bay and you can find them there for a more reasonable price. Aluminum is a snap to port. But I would practice a bit on your stock iron heads before doing the Aluminum L98s.

 

The info is greatly appreciated--THANKS GUYS!!!

I'll try and bone up on my thirdgen history! (HEH-HEH HEH-HEH--He said "bone"--U kow even as ridicously stupid as Beavis and Butthead were--I miss those guys!)LOL

It sounds like what I thought, I'd be better to go ahead and spend the extra money on a set of AFR's. That is still the "hot ticket" for an L98? Or is there something new that is better? (Boy--that's a loaded question!)