In March I picked up a 1968 convertible. Numbers matching. I am in the process of a frame off resto. The 327 is correct to the car and is a 350HP. The issue is it needs a rebuild. I would like suggestions on the course to take. I would like to keep the car close to original but also would like more performance. My thoughts are to build the motor with a hydraulic roller cam and new heads. I will keep the original heads if I sell the car. I guess I am looking for suggestions on the build components to get to 400-425HP keep it so my wife can drive it and I can still have fun. Hopefully this is not too tall a order to fill. I know the knowledge is here I want to here from you.
Thanks for all the input.

 

You do realize that the factory "350 HP" rating was for a test stand engine w/o any accessories as opposed to the net (as installed) HP quotes for 1972 and later engines? Also, your target HP is roughly what our flywheel HP was in SCCA B Production Vettes in the mid-70's running "race only" 331 cu in engines.

The biggest drawback to achieving your goals is the induction system and the exhaust system of the stock 1968 Vette. Your Vette should have come with a Quadra-Jet carburetor on a cast iron, low profile intake mated to some 1.94 intake double hump cast iron heads exhausting through cast iron exhaust manifolds into a 2 1/4" pipe dual exhaust system. Not exactly a free flowing system.

Although I love the Q-Jet for the street, if you want real HP, you'll need a Holley or Grant on a street performer intake to keep it under the stock hood. Go to a better intake and you'll need a BBC hood to accommodate the additional height a la the 1970-1972 LT-1 setup.

Cam selection is really based upon the drivetrain and rear end ratio. You didn't say what either of these two variables were, but don't expect to put a 6200-6500 RPM cam in a Vette designed to top out at 5800 RPM from the factory.

There are plenty of aftermarket aluminum heads to chose from that will outflow the stock heads from just off the seat to .600" of lift. (The stock heads peter out around .450" of lift.) Be sure to match the heads to the intake flow from the carb and manifold you choose.

Only thing left is to add headers and bigger exhaust pipes to make the system free flowing. (Don't add the factory side pipes. They look great, make plenty of noise, and only start to perform when the chambered exhaust started rusting out.)

With that out of the way, if you're willing to use nitrous, you could achieve your target HP levels in a street engine. Just be careful with the nitrous, or you'll have a lot of very expensive paper weights for bench racing.

If you've read to this point, I think that you realize that HP costs money...a lot of money when converting an older SBC over to modern components. The one great advantage the old 327/350 engine had was plenty of torque down low where you could use it on the street. I think that you would be happiest with a crate ZZ4 engine taking the place of the stock 327 engine. Plenty of torque across a broad spectrum, it fits the engine bay, and you can use your original Q-Jet and cast iron manifold if you like. That way you still have the original engine to swap back in when you sell.

Now, I'm an old geezer and YMMV; however, if it were my Vette, that's the way I'd go for the most fun per dollar spent. Good luck with rebuild.

 

Thank you for that insight. I will take your advise and research the ZZ4.

 

AFR 180 head 268/270 type cam HR good dual plane (weiand airstrike) with hood clearance, a 650 double pump Holley, 1.5/8 primary long tube headers should get you well into the 400hp range and be reliable and driveable. It will have some lope to it but nothing thats too out of hand.

 

Thanks for the detailed input. I really appreciate it.