Chevy Performance Q & A - Performance Q & A

Kevin McClelland Dec 1, 2009 0 Comment(s)

Hope this helps on your quest for two more lungs in your Chevette. Again, step up to the larger 4.3L over your wimpy 3.3L. After all that work, we don't want you to be disappointed!

Hot Cam Heritage
Q: I was a CHP subscriber about 10 years ago but had strayed from the flock. I've now returned to my roots, "getting into" the car hobby. Over the years I've modified the first car I purchased new, at 18, and it will probably be the only car I will ever own. It's an '84 Monte Carlo (non-SS), which currently has a 383 stroker with a one-piece seal, AFR 195cc heads (older PN 1038), an Edelbrock 3,500 Performer RPM Pro-Flo EFI system, a TCI Streetfighter TH350 transmission with a TCI 2,400-stall, an 11-inch breakaway converter, a GMPP PN 24502586 LT4 Hot Camshaft, and Dynomax 1 5/8-inch shorty headers into a 21/2-inch exhaust with Dynomax 2 1/2-inch Super-Turbo mufflers. The engine has flat-top SRP pistons rated 9.7 CR with 76cc chambers, but since my older AFRs have 74cc chambers, I assume the CR is closer to 9.8:1. Is this compression ratio adequate for use with the LT4 Hot Cam? This cam was designed for the LT1- and LT4-equipped Vettes to go SCCA stock-class road racing, so I was told, and those engines were 10.4 and 10.8 compression, respectively. Do I have enough compression at 9.8:1, providing my engine was zero-decked? I believe the CR may be closer to 9.5:1, since the engine was originally built with a Comp Cams 08-412-8 hydraulic roller with 212 degrees duration at 0.050 inch, and the engine builder didn't want the cranking compression to be excessive. Thank you much for your opinion, Kevin, and it's nice to be back home.
Steven Telkes
Saddle Brook, NJ

A: Welcome back. We're sure you'll feel warm and safe real soon. And we think your engine will love the Hot Cam. Let's go over a few facts.

The Hot engine was developed as an upgraded crate engine using the '96 LT4 long-block from the Vette. I was lucky enough to be involved with this project from its inception. What we were trying to do was create a higher-performance crate engine for the GMPP lineup. The ZZ3 was the big man on campus at the time, and the factory LT4 had great cylinder heads and a good amount of squeeze, as you mentioned. This engine lent itself to big power improvements with a simple camshaft swap, a dual-plane aluminum high-rise inlet, and a Holley 750-cfm carb. We had the engine development completed and the engine in my '65 El Camino. The car was back in Detroit for all the GM brass to drive and enjoy when the Flint Engine Plant decided not to take on any other engine combinations. It didn't make any sense running this engine down an off-line assembly system, because the cost to the public would be just too high. This is when GMPP released the Hot Cam package, which came complete with the cam, aluminum 1.6 rockers, LT4 springs, caps, spring seats, keepers, and valve seals. There was a different Show Room Stock camshaft that Wheel to Wheel developed for the SCCA race cars. This had several more degrees of duration and was designed around the mini tunnel-ram of the LT1s and LT4s.

Your 9.5-9.8:1 compression will do just fine with the Hot Cam. Compression isn't what it's all cracked up to be. If you have great airflow with the proper valve timing events, you can make really good power. The more efficient the cylinder heads are in both airflow and combustion efficiency, the less you have to rely on compression. The AFR heads always have good Brake Specific Fuel Consumption numbers on the dyno; this is a measurement of how well the engine turns fuel into work. The lower the numbers the more work you're getting out of the fuel. Install the Hot Cam without a worry. Enjoy!


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