Part throttle pinging - Team Camaro Tech
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post #1 of 25 (permalink) Old Jun 25th, 15, 09:19 AM Thread Starter
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Greg
 
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Part throttle pinging

I have been experiencing a part throttle pinging lately. It seem to occur right off of idle during part throttle acceleration. When I am running at cruising speeds I do not hear it and also don't hear anything under WOT. The pinging is not solid steady pinging, it is just a random one. Here is what I have tried to fix the problem:

1. Checked my timing and I have 14 degrees initial with this http://www.speedwaymotors.com/Speedw...utor,1688.html distributor. Retarding the initial timing doesn't seem to make a difference other than it making less HP.

2. Adjusted my carb idle mixture etc and made sure there isn't a power valve issue. No fuel leaking into the throttle body at all.

3. Checked for vacuum leaks and have none.

Here is what I am running in my engine:

350 bored .030 with flat top pistons with 4 valve reliefs.

64cc double bump heads with 1.6 roller rockers.

Isky 304 Megacam http://www.summitracing.com/parts/is...1304/overview/

Edlebrock Victor Jr. intake.

Holley 4010 750 double pumper.

Any suggestions are welcome.
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post #2 of 25 (permalink) Old Jun 25th, 15, 09:23 AM
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mike
 
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Re: Part throttle pinging

I once had a car with a similar distributor. They have adjustable vacuum advances. Take a long allen key and insert it in the vacuum port and turn it(not sure if it is in out out). I would almost guaranty that is the problem, too much vacuum advance.
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post #3 of 25 (permalink) Old Jun 25th, 15, 09:26 AM Thread Starter
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Re: Part throttle pinging

Quote:
Originally Posted by bigblockragtop View Post
I once had a car with a similar distributor. They have adjustable vacuum advances. Take a long allen key and insert it in the vacuum port and turn it(not sure if it is in out out). I would almost guaranty that is the problem, too much vacuum advance.
I forgot to add that I don't have the vacuum advance hooked up, it's capped off. I had it hooked up and made it worse.

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post #4 of 25 (permalink) Old Jun 25th, 15, 09:40 AM
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Re: Part throttle pinging

What gas are you using?

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post #5 of 25 (permalink) Old Jun 25th, 15, 09:51 AM
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Re: Part throttle pinging

So you don't have any hesitations when stepping on the throttle at any other times? If it happens every time you step on the throttle, try increasing the squirter size. If this condition only occurs right off throttle when cruising, try jetting up the primaries.

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post #6 of 25 (permalink) Old Jun 25th, 15, 11:04 AM Thread Starter
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Re: Part throttle pinging

Quote:
Originally Posted by Gbauer View Post
What gas are you using?
I am using 91 octane premium.

Also needed to add that it has just been a recent problem. Never had any issue before even running with 89 octane.

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post #7 of 25 (permalink) Old Jun 25th, 15, 11:06 AM Thread Starter
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Re: Part throttle pinging

Quote:
Originally Posted by DenRS View Post
So you don't have any hesitations when stepping on the throttle at any other times? If it happens every time you step on the throttle, try increasing the squirter size. If this condition only occurs right off throttle when cruising, try jetting up the primaries.
I do have a slight hesitation at times. It's kind of always been there but the pinging is a more recent thing. Squirter size could be a possibility. I have 79 jets in the primary and 81's in the secondary. Pretty big jets for a street car, possible I guess.

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post #8 of 25 (permalink) Old Jun 25th, 15, 11:25 AM
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Re: Part throttle pinging

Your timing mark could be off or you have more compression then you think. You also could be building up carbon on the pistons and valves which would cause higher compression and hot spots causing detonation. I am not a pro mechanic just throwing these ideas out there.
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post #9 of 25 (permalink) Old Jun 25th, 15, 11:30 AM
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Re: Part throttle pinging

Years ago we used Marvel mystery oil down the carb to get rid of carbon deposits. Sometimes running a pvc will suck a lot of oil fumes into the cylinder causing carbon deposits.
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post #10 of 25 (permalink) Old Jun 25th, 15, 11:50 AM Thread Starter
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Re: Part throttle pinging

I think Seafoam does the same thing. Be worth a try and cheap I guess.

One other thing I was thinking about was if my transition circuit on my carb was gunked up or something? Although I would think I would be past that when accelerating.

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post #11 of 25 (permalink) Old Jun 25th, 15, 01:19 PM
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Re: Part throttle pinging

I also noticed the jets do seem large and this could cause a rich condition which might help build up carbon. Do you run an air fuel ratio meter for tuning or how do the plugs look? Plugs could be to high of a heat range also??
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post #12 of 25 (permalink) Old Jun 25th, 15, 07:29 PM Thread Starter
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Re: Part throttle pinging

Quote:
Originally Posted by bigblockragtop View Post
I also noticed the jets do seem large and this could cause a rich condition which might help build up carbon. Do you run an air fuel ratio meter for tuning or how do the plugs look? Plugs could be to high of a heat range also??

The carb came new with 79's in primary's and secondaries. No air fuel ratio meter but at the track we found the best combo was 79/81. It doesn't seem to be too rich just from seat of the pants feeling. At this point I am almost willing to look at any option really.
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post #13 of 25 (permalink) Old Jun 25th, 15, 08:19 PM
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Re: Part throttle pinging

You know with that cam I don't see all of the specs but would think you have a lot of overlap decreasing your compression at lower RPM's. You sure it is ping and not something else happening?

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post #14 of 25 (permalink) Old Jun 25th, 15, 10:22 PM
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Re: Part throttle pinging

What do the plugs look like?
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post #15 of 25 (permalink) Old Jun 26th, 15, 03:37 AM Thread Starter
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Re: Part throttle pinging

I haven't got a chance to pull plugs or anything. Hopefully have some time this weekend. I may just pull my valve covers off and make sure there isn't anything obvious and also check the plugs.
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