71 350 and I am trying to work out the pinging. I have autolite 85's now ( I didnt install them). Autolite says stock should be 86's. Would a range colder help with the pinging? Thanks..

 

Going another range colder might help, but then you run the risk that the plug isn't hot enough to keep deposits burned off, which in turn creates poor performance and even more detonation.

Run a couple cans of Sea Foam thru the gas tank, just in case it's combustion chamber carbon buildup related. If it's really severe you may have to mainline it thru a small vacuum port.

 

Double check the tune up. Make sure the specs are correct, you may find the timing is off some.

 

You might want to check the grade of gas you're running. Although your car can run on regular, a higher grade of gas might take the pinging issue out. Also check to make sure the gap on your plugs is right.

Totally agree with Dan - check your timing.

 

Timing is at spec for a 4spd. I run 91 with lead based octane boost (chevron does seem better than shell). I have a quick fuel carb on that will be replace once I get my Q jet back from Sparky. Thanks for the carbon build up mention I was thinking of that cause the quick fuel runs rich. Seam foam, new plugs and proper built Q jet is the plan...Thanks

 

Not a factor. But, when you replace them, use AC R45S, gapped at .040".

Not likely.

If the plugs are "loading up" from in town (conservative) driving, you would need the hotter (R46S) plugs that were specified for 350 with AT.

10° BTDC @ 1100 RPM and idle speed @ 750 RPM, with no vacuum advance?

Centrifugal distributor advance = 1° @ 385 (2° @ 770 crankshaft) RPM and 16° @ 2000 (32° @ 4000 crankshaft) RPM?

If the above is in order, your balancer is the next place to look.

'71 350 should have no problem using 87 unleaded.

If it's due to a faulty power valve it could only be a factor at part throttle, when the vacuum advance is in play. If not, and your only complaint is "pinging", it's not that rich.

Two successive ¼ mile passes (or equivalent) will take care of any "carbon buildup" issues.

Norm

 

Norm, thanks for your pionts.

1) I have a pertronix unit installed so I need to reseach the plug gap. I'm thinking around .060

2) Timing is set at 10 btdc at idle with advance plugged. I've had the car 6 weeks and have not looked into the timing above idle. It appears I set it wrong, not being set at 1100 rpm.

3) Motor is not stock fresh rebuild with builder specs showing 9.8 cr. Large valves 2.07 / 1.60, bigger cam, performer manifold.

4) Since my Q jet is on its way back I've been living with the carb, it gets hard to start when hot and has a raw fuel smell at idle and low speeds.


thanks again...

 

Doesn't change anything in the combustion chamber, or its spark requirements.

Won't make it run any better than the factory specified .040" gap.

There is no advantage in "upgrading" an ignition system that can already handle anything the engine will ever need.

That makes the above timing specs useless.

The "band aid" is to retard it until it stops pinging. Better would be a curve, custom tailored to your application.

Ideally, you'd need to match the compression to the cam. Or if you cannot, to match the cam to the compression.

Then have a curve made to fit the resulting specs.

Norm

 

I would be intersted to know what your cranking compression is.