Pinging driving me nuts
Melting Slicks
Joined: Jul 2004
Posts: 2,867
Likes: 195
From: Maryland
How much total advance are you running, and how quick is your curve coming in?
I think Lars has nailed it. Bet the mechanical advance is a little too rapid for the engine. Suggest a distributor blueprint to engines spec and recurve.
I think Lars has nailed it. Bet the mechanical advance is a little too rapid for the engine. Suggest a distributor blueprint to engines spec and recurve.
Thread Starter
Pro
Joined: Nov 2001
Posts: 684
Likes: 0
From: Winnipeg Manitoba
This weekend I am going to have a look at the plugs and then follow up on Lars suggestion. The problem just started happening out of the blue, even though I have made no changes at all. Will see how it goes. Thanks again
Safety Car
Joined: Jun 2002
Posts: 4,757
Likes: 2,508
From: Buckeye, AZ
St. Jude Donor '12-'13
Back in mid-late 70s every car did this. The solution back then was to retard the timing slightly. My stock '78 used to do it, but putting in a true dual exhaust system with high flow cats cured it. Damn cat back pressure!
Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
Another point about fuel....
I don't know if it happens in Canada, but it is common practice to have a different formula for fuel dependant on the season... (winter/summer)
Also, with the cost of fuel escalating, some of the smaller independant distributors vary who they obtain their fuel from, and the quality can often be different, even though it has the same advertised rating.
Also, be wary of Ethanol blended fuels. They may be a bit cheaper due to government subsidies to encourage a "greener" philosophy, but it doesn't have the same combustability as fossil fuel based petroleum.
If it just started happening "out of the blue" and your timing is spot on, I would still be VERY suspicious about fuel quality. If your other cars are late models with computer controllers, they have engine knock sensors to retard timing. These ol' girls don't cater for too much variance in fuel quality when the timing is set for performance.
tom
I don't know if it happens in Canada, but it is common practice to have a different formula for fuel dependant on the season... (winter/summer)
Also, with the cost of fuel escalating, some of the smaller independant distributors vary who they obtain their fuel from, and the quality can often be different, even though it has the same advertised rating.
Also, be wary of Ethanol blended fuels. They may be a bit cheaper due to government subsidies to encourage a "greener" philosophy, but it doesn't have the same combustability as fossil fuel based petroleum.
If it just started happening "out of the blue" and your timing is spot on, I would still be VERY suspicious about fuel quality. If your other cars are late models with computer controllers, they have engine knock sensors to retard timing. These ol' girls don't cater for too much variance in fuel quality when the timing is set for performance.
tom
Last edited by OzzyTom; Apr 18, 2007 at 11:31 PM.
Thread Starter
Pro
Joined: Nov 2001
Posts: 684
Likes: 0
From: Winnipeg Manitoba
Well I did some further investigation last night on the pinging problem. I checked everything again as stated and this was fine, I disconnected the vacuum hose from the vacuum advance and then took the car out for a drive and there was no pining at all. Is it possible that the stock vacuum advance is the problem and needs to be replaced. Would I go with a stock replacement or and adjustable vacuum advance ? Also where is the serial number on the distributor, I belive that I would need this to insure that I get the correct vacuum advance ?
Thanks
Thanks
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
I had pinging after a swap to a ZZ4 engine in my 80. I replaced the ZZ4 vacuum advance with one that pulled in a bit less advance and the issue went away.
The problem in my car would show up worse at cruise with the throttle open a bit which caused high vacuum and increased engine load/cyclinder presure.
The problem in my car would show up worse at cruise with the throttle open a bit which caused high vacuum and increased engine load/cyclinder presure.
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Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
It sounds like your car is stock. Does it have the stock air cleaner housing and exhaust hot air pickup? I had a '78 (non-Vette) that pinged on the highway. The problem turned out to be the temp sensor in the housing was pulling heated air into it even when the car was at operating temp. I adjusted it so that the heated air was only used until the engine was just coming to operating temp and the problem went away.
Thread Starter
Pro
Joined: Nov 2001
Posts: 684
Likes: 0
From: Winnipeg Manitoba
its all stock, the ignition system is new and the emissions all tested fine. Car runs and starts perfect with the exception of the pining that happens on a incline. The other day when I disconnected the hose the vacuum advance and test drove it, there was not one ping. Leads me to believe that the vacuum advance is the problem.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
With an adjustable timing light, check and see how much vacuum advance your stock unit is pulling in. Many stock units will pulll over 20 degrees of vacuum advance in. My Vacuum Advance Specs paper lists various units with their range - you can select one that only pulls in about 17 degrees of advance to help with your problem. E-mail me for a copy of the paper with the specs and part numbers:
V8FastCars@msn.com
Lars
V8FastCars@msn.com
Lars
Thread Starter
Pro
Joined: Nov 2001
Posts: 684
Likes: 0
From: Winnipeg Manitoba
Thanks for the response Lars, I have a copy of your paper and was looking at it last night. The car was running good up till the pinging started. Went through everything again last night and then decided to pull the vacuum hose from the vacuum advance and then the car did not ping while climbing a grade. I figured that the vacuum advance (non adjustable) was the culprit. The whole vehicle is stock and this is the first time that I have had to deal with a suspicious vacuum advance. I will see what my local parts store (napa) has avaialble based on 17 degrees, I will also get the serial number of my distributor and cross ref it to. Thanks to everyone for your assistance. I will update you on the progress.
