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Mail From: Lee=Atkinson%Port=Perf%Port=(email redacted)

>Subject: Knocking in my '65 289 motor

>I have a '65 Mustang, 289, with 56,000 miles. It sat idle for a few years
>before I resurrected it last year. Now it runs fine, except that it has
>begun knocking (pre-ignition).
>How can I eliminate knocking? How about if I use a higher octane no-lead
>gas? What will be the damage? How long will it take for the damage to
>appear? If I think the engine needs rebuilt eventually anyway, why not use
>no-lead until I rebuild it?

>Mike

Mike, my suggestions are;
1. Check your base timing
With a timing light and the vacuum advance disconnected, check that
you get about 10' BTDC spark at idle. You may eliminate the knock
by lowering to around 5' BTDC.
2. Check your mechanical advance; Run the motor up to about 3000 RPM with
the vacuum advance disconnected; you should see the spark start earlier,
like around 30' BTDC (check your specs to make sure !). This probably
isn't causing your Knock but its a good thing to check.
3. Make sure the distributor vacuum "advance" is working
If the knocking occurs only on hard acceleration, this may be your
problem. The vacuum advance lowers the overall advance under high
load (low vacuum).
Check the piping from to the spark advance, could be that the tube has
deteriorated or fallen off. I don't know of a good way to check that
the advance otherwise except to hook up a vacuum source and watch the
spark move in or out.
4. If the problem is knocking at idle, or when you shut off the car,
your Idle speed may be set too high.
5. If your carb is running really lean this could cause knocking. Don't
modify anything, just make sure its clean.

I run 87 Octane gas on my 351c (which is probably around 9.3:1 CR
with its open chamber 4v heads) and don't have any problem with
knock, even at WOT. YMMV....

Good luck--Lee