Questions and Answers

Chevrolet Corvette In A Fine Fix Q. I recently discovered my 1969 Chevrolet Corvette with a 1968 327 cid small block had a stock head on one side and a high performance head on the other. I installed the high performance head I needed, however, the car is backfiring through the carburetor when I lay on the accelerator.

I also noticed the engine makes cyclical vibration every two to three seconds. I tried rotating my distributor just a bit to get the "loping" out at idle, but I don't have acceleration power. In the process of making adjustments, I've tweaked the needle valves on my carburetor.

Now I'm afraid the timing and mixture are out of whack. Where should I start to undo this mess I've made? I'd feel silly taking my car to someone for adjustments I can make myself. What do you think?

Best Regards,
W. Carswell
Dallas, TX

A. Is the backfire happening every engine revolution or just one time when hitting gas? Is it possible for a camshaft lobe to be worn out or a broken valve spring or rocker arm? All these items would and could give you a backfire that is constant every time that cylinder fires.

If you think it's just the engine out of specs, set the base timing first. Then re-tweak the carburetor mixture for a smooth idle and take it for a spin. If you still have no power, try looking at the distributor advance weights for being stuck or possibly a bad carburetor.