November 2010 Chevy High Performance Q&A - Performance Q&A

Kevin McClelland Oct 12, 2010 0 Comment(s)
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A: Putting a basket case back together can really get on your nerves, even if you've been working on them since they were built. The factory assembly manual you have gives you general specifications that GM used as the car went down the assembly line (e.g., measurements for moldings, emblems, body gaps), but to get the hard-core info you're looking for, you need a Fisher Body Manual for '69 Chevrolet passenger cars. The GM Fisher Body Service and Construction Manuals are very helpful when doing a total rebuild, showing nearly everything from the upholstery styles to the dash and door assemblies. They also include adjustment and installation procedures-this is going to be your best source of information for assembling your Camaro. Check with Greg's Automotive for the Fisher Body Manual, PN 69FB. They are very reasonably priced at $25 and can be ordered online.

Dual 4 Pots
Q: I recently built a 383 stroker motor with a 9.4:1 compression ratio. It consists of the following: a 3.750-inch stroke cast steel crank with 5.700-inch CNC forged I-beam rods, forged flat-top pistons, and AFR 195cc heads. Up top, I'm running an RPM Air-Gap manifold with a Holley 750-cfm vacuum secondary carb. The camshaft is a Comp hydraulic roller with a lift of 0.502 inch intake and 0.520 inch on the exhaust. At 0.050 inch tappet lift it has duration of 224/236. This combination on an engine dyno turns out 491 hp at 6,000 rpm and 489 lb-ft of torque at 4,600 rpm. I would really like to use a dual-carb setup just for something different, plus they look way cool-does it run off just one carb at cruise or is it working off both? Edelbrock offers a kit with 600-cfm carbs. I just wonder if this would be too much carburetion for this engine combination? Thanks in advance for your help, Great mag!
Lon Ketchum
Via email

A: Dual quads would be way cool on your 383. Edelbrock offers two kits for small-block Chevys. The original C-26 Dual Quad manifold is still around after some four decades! Several years ago, Edelbrock stepped up to support the vintage market by producing an RPM Air-Gap Dual Quad version, which features the distinctive Air-Gap design to give you cool, dense intake charges, and larger and taller runners for great airflow. The RPM Dual Quad is 15/8-inch taller at the carb flange over the C-26, which could cause hood clearance issues. This manifold and dual quad setup will not perform as well as the single four-barrel RPM Air-Gap, but I don't think that's what you're about. With the new RPM design you should see minimal power losses.

Edelbrock offers a complete RPM Dual Quad manifold and carburetor kit under PN 2025. This package features their Thunder Series AVS 500-cfm carbs, progressive throttle linkage, fuel lines, and intake gaskets. These 500-cfm carburetors will be perfect for your application. The secondaries on these carbs feature an air valve that tailors the airflow to the demand of the engine. The high-tech progressive linkage offered can be set up for either progressive or 1:1 ratios. In the progressive mode, the rear carburetor is for slow-speed driving (up to 20 degrees of throttle opening). Past that point, it brings in the front carb as well, until you reach wide-open throttle. If you're looking for a more aggressive throttle response you can set the linkage to 1:1, which opens the carbs in unison.

Check with Edelbrock for more information. Have fun-your 383 will have some real authority with dual quads atop it.

LS Monte
Q: I'm in college and your magazine is the only thing I insist on reading cover to cover. A few years ago I bought an '85 Monte Carlo CL from a junkyard and have been converting it into a purely dragstrip car. I have a good Turbo 350 transmission and 12-bolt GM rearend (I need to remove the posi and install a full locker). The engine is where I fall short.


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