December 2011 Chevy High Performance Q&A

Kevin McClelland Oct 24, 2011 0 Comment(s)
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Pickup in the Sandbox

Q. I have a ’76 Chevy C10 shortbed truck, “The Puzzle”, that I would like to do a budget build on. It currently has a 5.7L 350 four-bolt main with a TH350 transmission that’s all stock. Even though it’s the last year for emissions, I still needed to get it registered under my name so I revived it by doing a basic tune-up and carburetor replacement and passed California emissions with flying colors.

I would like to have the stock block rebuilt with Vortec heads, a Vortec intake for the Q-Jet 750 carburetor, and a COMP Cams camshaft. On the exhaust side, long-tube headers with Magnaflow dual mufflers and an X-Pipe. I would like to see maybe getting close to 375 for both power and torque, but I do have some questions: Is the Vortec intake manifold gasket shaped different than a regular intake gasket? Would a Fel-Pro 0.015-inch-thick rubber-coated shim gasket bump up the compression? Is there much of a difference between the 262 and 268 camshafts? Would you recommend I use a 1.6:1 rolled tipped rocker? Can I use the stock Vortec springs for the COMP Cams camshaft or purchase it as a set? I read somewhere to use black rubber press-on seals with white Teflon inner liners and to stay away from the all-white Teflon seals. Is there any truth in that? On the transmission side of things, would I have to change the stall converter for the particular camshaft or would you recommend I go ahead and see about getting the transmission replaced for a 700-R4, since the truck will see occasional daily use? How much of a difference do 13/4- or 15/8-inch long-tube headers make?

I know my questions sound elementary, but when you’re floating around looking for pirates, you don’t have too many resources. This will be my first engine build, and I’d certainly appreciate any guidance you can provide. I’m no expert but certainly know my way around a garage. Thank you for a great magazine! Keep up the great work.

CWO2 Isai C. Palacios
USS Green Bay
Deployed to the Sandbox

A. There are no elementary questions when it comes to the specifics of an engine build. You must get it right the first time or pay the price later. Let’s see if we can answer some of these important questions.

A Vortec upgrade to your stock ’76 short-block is a good foundation for the power level you’re shooting for. Yes, the Vortec intake gaskets differ from a standard Gen I small-block port and bolt pattern. The factory Vortec gaskets are plastic framed with silicone rubber-sealing O-rings built into them. We’d go with the Fel-Pro Print-o-seal gasket for the Vortec application (sold under Fel-Pro PN Z1255 and can be picked up from Summit Racing under PN FPP-1255). As for the 0.015-inch-thick head gaskets, they are only slightly thinner than the factory 0.018 steel-shim head gaskets that are originally used on your small-block. The main increase in compression is going to be from the combustion chamber reduction from 76 to 64 cc of the Vortec heads. Even the rubber-coated steel-shim Fel-Pros are very unforgiving to deck surface imperfections. If you wish to run a thin head gasket we’d recommend a factory GM composition 0.028-inch head gasket (PN 10105117). These gaskets were used on the iron-headed late-model Gen I small-blocks. Using the factory ’76 dished piston, these head gaskets, and the Vortec heads, you will have right around 9.0:1 compression. This will work very well with your build and pulling around your truck.

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