Q: Timing Adjustments
I am having a problem setting my timing on my car to the indicated specifications. What do I need to do to fix the knocking on my HO engine?
A: I’ve never had that much of a problem with the timing on my 400. But I don’t pay that close attention to the timing at idle. For mechanical advance (with the vacuum advance hose to the distributer removed and plugged), I set the timing at 32 degrees BTDC at about 2600 RPM (you’ll need some timing tape for this). Once you set the mechanical advance, disconnect the vacuum advance hose at the carburator end and hook up a vacuum gauge to the carb that you can put inside the car. Then go out for a little run and write down the maximum vacuum when running at a constant speed with the engine at 2500, 3000, 3500, and 4000 RPM (make sure the road is somewhat flat). Go back and hook up your timing light again, set the engine speed at about 2600 RPM, connect a vacuum pump to the vacuum advance and pump it up to the your max vacuum reading you read in the car. Your total advance should be 50 degrees at this point (that’s what I set mine too, I know people that go higher, but not much). If you have a distributor with adjustable vacuum advance you can adjust it until you get 50 degrees. If your motor is spark knocking you’ll have to back off on the timing until it doesn’t. But that ussually means there is something else wrong, like your vacuum advance is advancing your timing too much, you’re running too lean a fuel mixture at max advance, or you’re running to high of a compression ratio for the fuel you’re using. I think most people run to high compression for street gas. I don’t think you should run more than 9.5:1 on plain old 93 octane. And most people with older cars have compression ratios over 10:1………………………………….spark knock city……………… If the production timing marks weren’t cast right into the timing chain cover, I would have taken them off a long time ago. Timing tape is pretty cheap and alot more accurate. That’s my 2 cents worth anyway.
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Content last modified: January 15, 2014 at 9:46 pm