campw

I have a 82 SC with 103,000 miles on it. Just recently i began to notice some slight knocking noise when i "stomp on it". Also it only seems to happen in hot weather. I live in Los Angeles area. I had the car smogged and was wondering if a change in timing might be the problem. Anyone have any thoughts/suggestions?

Steve Weiner-Rennsport Systems

Hi:

Given the California 91 octane fuel you have and the occurrances in hot weather, you are likely experiencing some detonation and that is NOT good.

With 103K on the odometer, you probably have some carbon buildup that raises the effective compression ratio enough to make the engine more octane sensitive. You migh try some different brands of fuel to see if one works better than another for you bearing mind that winter fuels all carry more oxygenate than other times of the year.
This makes the engine run leaner than normal and you also might check your idle CO to see that its set slightly richer than spec.

By all means, lift your foot off the accelerator anytime you hear that sound so you do not buy new P/C's sooner than you need to.

slomarsh

Here is SoCal you can find 100 octane from union 76. Try a tank or mix it with 91oct and see if the knock goes away. <img src="graemlins/a_smil17.gif" border="0" alt="[blabla]" />