Does this mean we always do this? Not when you're working around an existing combination like yours. We've built many an engine doing exactly what you are describing with great success. Did it make the most power that it could have made with a properly designed piston? Probably not. But we can't always have our cake and eat it too. Good luck with your little 350.
Q: My '71 Chevelle has a 350 and a four-speed. The engine and transmission are out of a '76 Chevy pickup. It's lacking the power I want, so I would like to do some performance upgrades to the engine. I'd also like to use positraction. I would like to keep a budget of around $1,500 to $2,000. Can you help?
A: Your quest is the most popular upgrade around. First, you must have a sound short-block. The short-block of your '76 truck engine must be in very good condition. Also, if there is a ridge at the top of the cylinder bore, you will break the rings when you extend the rpm range of your engine. The bottom end of your engine is built with cast dish pistons and a cast-iron crankshaft. The max engine speed this short-block will live with is about 6,000 rpm. Also, you must keep this engine out of detonation. Nothing kills cast components faster than overspeed and detonation. Please make sure your short-block is a useable victim before installing components that will raise the output by 100-plus horsepower and the engine speed by at least 1,000 rpm.
Once you're confident that you have the building blocks of a nice little small-block, choose your components wisely to stay within your $2,000 budget. Look for an affordable aluminum street head, intake manifold, carburetor, headers, and camshaft package. Your stock truck engine is probably kicking out a whopping 250 hp, and you should get yourself a safe, driveable 350 hp out of the stock short-block. Hopefully, when you installed this engine in your Chevelle you upgraded a few things like headers and dual exhaust. This would save your budget and leave you more to spend on much-needed new hardware.
We've picked a package of components that will not break your budget and really wake up your Chevelle's mild personality. Start with a set of Summit Racing Aluminum Street heads. These feature 170cc inlet ports and 62cc combustion chambers, and are fully assembled with valvesprings that will accommodate a flat-tappet camshaft with a max lift of 0.480 inch. With the 62cc combustion chambers it will kick your compression ratio up to slightly over 9.0:1. These heads matched with a Comp Cams XE268 camshaft and lifter kit PN CL12-242-2, an Edelbrock RPM Air-Gap PN 7501, and an Edelbrock Performer 750-cfm carburetor PN 1407, will round out the top end. To install the aluminum heads you'll need aftermarket head bolts and pushrods. ARP offers a very nice set of affordable head bolts with hardened washers under PN 134-3601. You'll also need hardened pushrods to mate with the guideplates on the new aluminum heads. Check out Comp Cams PN 7812-16 stock-length, 5/16-inch-diameter pushrods. To seal everything up you will need an engine gasket set from Fel-Pro PN QKS2600; this is a complete engine gasket set to give you everything you need for the project at a decent price. Finally, to light your fire, step up your ignition system with an MSD Street Fire HEI PN 8362.
All of these new components come to a grand total of $1,892.70, using Summit's standard everyday prices. From time to time you can find that many of the mail-order houses run discount coupons that can save you up to 30 percent. With the extra couple of dollars you could squeeze in a set of headers and spark plug wires.
For your posi, you'll need to wait and save for the next upgrade. This engine package will give you a very reliable 330-350 hp that will make your Chevelle a whole lot more fun. Enjoy
Sources: arp-bolts.com, compcams.com, edelbrock.com, federal-mogul.com, msdignition.com, summitracing.com