Chevy Car Questions & Answers - Performance Q&A

Kevin McClelland Sep 1, 2009 0 Comment(s)

A: The ZZ383 is a great choice for your Monte buildup. The cylinder heads used on the ZZ383 originally came from the LT4 Corvette engine. GM Performance took a set of LT4 production heads and had them ported, tested, then digitized. These digitized ports were then turned into tooling and cast up as the Fast Burn cylinder heads. So, truly, you have CNC-ported LT4 cylinder heads with an as-cast finish. Isn't technology wonderful?

When GM tested this engine, it used 13/4-inch headers because the header tube lined up with the roof of the exhaust port. Several manufacturers produce a D-shaped exhaust port header-the trick is to find a set for your G-body. Hedman Hedders has two very nice full-length headers in its Hustler racing line. We've used the 15/8-inch set (PN 65218) in our stocker, and they clear the angle plugs and fit the raised roof exhaust port. The only issue with these headers is they don't fit with A/C. The header tube routing on the passenger side will hit the A/C box on the firewall. The 13/4-inch header is PN 65217; both have very good clearance around frame and suspension components. As for an X-pipe, check out the X-Treme Exhaust Equalizer (PN 18813 for a 21/2-inch system). This is a very nice X with a fully hand-welded junction, which aids in the scavenging of exhaust gases and gives you that unique X-pipe exhaust note. If the A/C is an issue, check with Stahl for custom headers that will clear the A/C and specific CNC header flanges to fit the Fast Burn cylinder heads.

Mufflers are a personal preference. There are many quality high-flow mufflers on the market today, and each sounds different. The floorpan on your Monte has limited room for large, quiet mufflers. There is a little room under the rear seat of the car, and you can install 4-inch-thick, 10-inch-wide case mufflers. This isn't going to stop much sound. Check with Borla, Flowmaster, and Magnaflow for their recommendation for that type of space. Then add tailpipe resonators (secondary mufflers) to help cut down the noise. I've built many systems with this layout and had very good results quieting down nasty exhaust notes.

Finally, this engine would love a Q-jet. However, we'd choke it down with a Performer inlet. Try that Performer RPM PN 7104 you mentioned. It will supply that engine with the airflow that the cylinder heads and camshaft need. We also like the traditional Gen I inlet bolt layout. The dozen 3/8-inch bolts holding down the manifold is better than the eight 5/16-inch bolts of the Vortec design. Good luck with your Monte!
Sources: borla.com
flowmastermufflers.com
hedman.com
magnaflow.com
stahlheaders.com

Tick, Tick, Tick
Q: I have about 500 miles on my new 350 Chevy ZZ4 crate engine and have followed the GMPP break-in procedure to the letter. I used Valvoline 20W-50 Racing Oil (with zinc) and prelubed the engine prior to initial startup. The valves have been ticking since startup, so I tried adjusting the valves using the EO-IC procedure, zero lash, and then a half-turn down from there. The valves still tick slightly, just as they did before the adjustment. Any help correcting this problem would be greatly appreciated.
Paul Biddle
via email

A: You're probably not going to like our answer. For the most part, slight tappet noise is normal with the ZZ4 camshaft. The acceleration rates on the inlet lobe of that camshaft are pushed out to the max. With the very short duration number of 208 at 0.050 inch lift, and max lift numbers of 0.474 inch, you won't find a higher-lift cam with that duration in the aftermarket. That camshaft was originally designed for the ZZ3, which was also used at the time for the H.O. 350 Camaro emissions-legal engine package. To achieve 308 hp through the cats, the production exhaust manifolds, and all the emissions equipment of an '87 Camaro, GM had to pull a few tricks out of the bag. Pushing the camshaft without increasing the duration was one of them.

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