Mailbag: Tuning Tips for a Modified Chevy 350



Q: I have a 1973 Nova with a GM 350 crate engine.

The engine has Trick Flow 23° cylinder heads, a Lunati cam, Edelbrock Performer intake, an Edelbrock Performer 600 cfm carb, and an MSD HEI distributor.

The car also has a Turbo 350 transmission with a 2,500 stall lockup converter, Richmond 3.73 gears in the rear axle, and 3-inch dual exhaust.

The problem is that I expect this ride to burn rubber, but I can barely make the tires chirp.

I was thinking about boring the engine out .030 over and adding a Trick Flow cam (246°/254° duration at .050 inches, .495 inch/.510 inch lift), but I don’t know if my transmission can handle that. Help me out, please. I do race in this car and hate to lose!

A: Looking over your list, we feel you have all the right pieces in place to make good power.

We think your problem is probably in the tune.

Take a look at your ignition timing—initial, centrifugal (mechanical advance) curve, and total—and check for low cylinder pressure (cranking compression).

If your total timing is too high, the cylinder pressure is between 120-130 psi, and the carb is neither adjusted nor calibrated, the engine will not give you the power you’re looking for.

The Edelbrock carb may be a little small for this application. You may want to look at one of Edelbrock’s 750 cfm models instead.

You really don’t need an overbore unless there’s a ring-seal problem and you probably don’t need the larger cam either. Just tune what you have and you’ll be in business.

This is another in a series of weekly Q&A Mailbag sessions with Summit Racing’s tech department, in which there are hundreds more. Click here to see them all.

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  1. The inability to “burn rubber” is not going to be helped by a bigger carburetor, given that a bigger carburetor will definitely not help low-end torque. In any case, a 750 Edelbrock isn’t going to flow more at the low-end than a 600 Edelbrock, given that they’re vacuum secondaries.

  2. With the information that has been looked at, I would have to surmise the timing is not advanced enough. This could also be made worse by your cam not installed properly. It sounds like the cam is retarded(opening the valves late) and/or ignition timing also retarded. I would try the easiest and trying advancing the ignition timing to see if the engine responds.

  3. Air restrictions and fuel I use 750 holley carb easy to tune running to lean more air more fuel also run hot sparkplug timing 12 at idle 36 max advanced this will help

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