July 2010 Chevy High Performance Letters - Performance Q & A

Kevin McClelland May 24, 2010 0 Comment(s)
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With this camshaft, your compression ratio, and aluminum heads, you should be able to run this engine on pump gas. We'd start with 30 degrees total timing and check the performance. Remember, when jetting race-type engines on pump gas, you need to increase the main jet around 6 to 8 jets sizes, compared with proper jetting on race gas. Pump gas is an oxygenated fuel carrying its own oxygen. Start safe and jet accordingly.

As for power, you should see tons of torque; we'd target the horsepower to come in at 580 to 600 on pump gas. Yes, you could push the power much higher with a larger camshaft, more compression, and larger inlet track; however, this will be one fun street brawler that will push your S-10 around with ease. Good luck, and don't scare yourself.
Source: lunatipower.com

LT4 Secret
Q: I am upgrading my ZZ4 after many years and good performance. I'm going 0.030-inch over, good rod bolts, and the crank is still standard. I've upped the valve sizes and was lucky enough to score a new Chevy Hot cam and new 1.6 Chevy rockers w/studs (no lock nuts) at E-Town. At home I opened the stud box, and to my dismay, the studs are 10mm (as are the rockers) with a small threaded stud on the end. I have tried everywhere to find 10mm studs with lock nuts so that I can make the valves adjustable, but no luck. Can you bail me out? I look forward to your answers every month, as they are the most informative of all the mags. Thanks.
Rich Larrimore
Via email

A: You have run into the little LT4 secret. The valvetrain on the one-year-only (1996) LT4 is a net-lash design. What this means is that those 10mm rocker studs have a mating nut that tightens against that small stud (forget the size) at the end of the rocker stud. The nut bottoms out on the shank of the rocker stud applying a specific amount of lifter preload.

First, you didn't mention if you got the rocker stud nuts with your collection of parts. You'll need to order a set of nuts. Next, you need to mock up the valvetrain of every cylinder. You can adjust the valves by adding shims under the rocker studs to adjust the lifter preload. We ran into the same situation on our LT4 bracket engine in our Malibu Wagon. We cut the deck down to 9.00 inches, clipped the heads by approximately 0.020-inch, and run thin 0.028-inch head gaskets to get the compression up to 11:1 with a flat-top piston. This put too much preload on the valvetrain. Using 7/16-inch AN-style washers, we were able to get between 1/4 and 1/2 turn of preload on each lifter. The AN washers come in two thicknesses, 0.032- and 0.063-inch. You can pick up these washers in bulk from Pegasus Auto Racing Supplies under PN AN960-716L (0.032-inch) and AN960-716 (0.063-inch). Pegasus is a great source for racing hardware and little trick components that make race car fabrication a breeze. Mainly catering to the road race community, but many of the parts don't know if they are going straight or around turns.

The LT4 rockers are extremely strong and have the least amount of deflection of any aluminum roller rocker on the market. GM really pushed the envelope with these rockers, as they are the only aluminum roller rocker ever offered on a production engine. Hope this helps in getting your engine together. Good luck with your ZZ4 upgrade.
Source: pegasusautoracing.com


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