340 Pinging using 94

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dterry1 said:
I have a 340 in my 72' Duster

I have had some pinging issues recently using 94 octane pump gas, and am going one of two ways to try and resolve the problem. I just wanted to post it on here and see what y'all think.

1. Lead substitute fuel additive/octane booster
2. Use a lower octane fuel (91,89,87)

I have tried retarding the timing to help with the early detonation, this helped a little bit. The pinging is not as severe, but it is still there.

Let me know what y'all think, your knowledge is much appreciated!
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Definately sounds like ignition is going to advanced.
 
str12-340 said:
Just to say this clearly - if the engine has stock compression - whether it's 10.5:1 (nominal) or less, it shouldn't ping on premium pump gas. Is it possible that you just got a crappy batch of gas that isn't actually 94 octane? How much gas have you run through the engine running like this?
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about 3 tanks
 
Update:

After adjusting the idle mixture screws, and retarding the timing, I got it to the point where it no longer pings at ~2k rpm.

But it does ping as I let off the gas and the car is coming down in RPM, around the 1,100 - 1,500 range.

The pinging is much quieter, but now is in the lower rpm range, and only when I let off the gas.

The spark knock noise is down to about 1/10th of what it was, it's just a slight tick now. As before it was quite loud.

Also, I tried changing the spark plugs out, and it ran TERRIBLE, and when I put the old ones back in it was fine again, not sure why or how.
 
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No, you do not want or need colder plugs for this engine. Correct heat range is 5 in NGK or equivalent.

The description in post #34 does not sound like pinging. Pinging occurs under load, not when you back off.
 
What did you set the timing too? Doing this might mask over advancing (possibly too soon) which could be aiding to your issue.

Have you checked to see how much and when the advance come is?

If you don't understand what I'm asking, please let us know. You will get help on understanding on how to do so.
 
What octane? 91? 93?

First things first... check the cranking compression. If it's less than 180psi... its definitely a tune issue and not an octane issue. Imo but theres still other factors to consider.

Disconnect the vac advance, check timing. Idle and 2000-3000 rpm, check timing.

Let us know what both the cranking compression is and the timing, initial and full advance, with vac advance unplugged from the distributor.
then check the timing full advance with the vac advance hooked up.

Report back.
 
It's doing it while decelerating now? Are you sure it's a ping and not a loud exhaust tick from a leak that you are hearing?
 
Here is wat we need to know to begin to solve this problem.

What is the cranking compression?
What is the initial and total timing? And, when is it all in by?
What gears are you running? And, with what transmission? And, with what height tires?
What carburetor and does the tune seem dialed in? Or, are you experiencing any other issues?
What is the typical average operating temp of the car? ex, 195 deg..
What RPM are you running at 55-60mph.

Without that info, you are pissing in the wind.

I would get the timing locked down first. Set the total to 34 degrees to begin and make sure it is coming in no earlier than earlier than your 60mph rpm.
 
Lotsa unanswered questions here. I'm sittin back waitin.
 
It's been asked, but not answered. What distributor are you running? I had a buddy with a stone stock '60 340 four speed Barracuda. It was pinging and he thought is was distributor (stock dual point). I had a fresh one on the shelf so we swapped them and the pinging went away. The only obvious thing I found when I took it apart was a vacuum advance plate that was froze up from dried grease. Fixed all that and it was still pinging. I had no way to measure it, but guessed that it was the point cam. Replaced it with one from another dual point and it fixed the problem. I didn't have a dwell meter to check it, but I suspect that was way off due to wear in the cam.
 
I don't have much time today or tomorrow. So I will gather all of the needed information over the weekend.

The distributor is stock

I will come back with my initial timing, total timing, cranking compression, all in RPM.

some of the other information requested that I have:
Trans is a 727
Carb is a Holley 650
Average Operating Temp. is 160-165 F
At 55-60 MPH I am around about 3k
 
How bout a video, - cuz we all have our crystal balls, and magic 8 balls out for detailing, - so some ... help is needed.
We're 40 posts in, and absolutely no farther ahead, cuz some are assuming you actually know what "ping" sounds like .
Vehicles don't ping decelerating.
 
inertia said:
How bout a video, - cuz we all have our crystal balls, and magic 8 balls out for detailing, - so some ... help is needed.
We're 40 posts in, and absolutely no farther ahead, cuz some are assuming you actually know what "ping" sounds like .
Vehicles don't ping decelerating.
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I can take a video.

For the "Vehicles don't ping decelerating", why is that? The engine is still firing while decelerating, it's just doing so at a lower RPM. And if the detonation is now occurring at a lower RPM after retarding the timing, I don't see how it's out of the question.

Now I could very well be wrong, and I am not using experience to justify my thoughts, just logic.
 
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