Exhaust Popping
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Exhaust Popping
A question guys...
I just finished rebuilding my 1978 PCR; ZZ383, M22, etc. I had Allen's build a chambered system for the car connected to a set of McJacks headers... I'm getting popping out of the exhaust when I take my foot off the gas and am coasting.. Is this normal, or should I be looking for something which causes this?
Thx,
Joel
I just finished rebuilding my 1978 PCR; ZZ383, M22, etc. I had Allen's build a chambered system for the car connected to a set of McJacks headers... I'm getting popping out of the exhaust when I take my foot off the gas and am coasting.. Is this normal, or should I be looking for something which causes this?
Thx,
Joel
Safety Car
Joined: Mar 2007
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From: Bridgewater nj
A question guys...
I just finished rebuilding my 1978 PCR; ZZ383, M22, etc. I had Allen's build a chambered system for the car connected to a set of McJacks headers... I'm getting popping out of the exhaust when I take my foot off the gas and am coasting.. Is this normal, or should I be looking for something which causes this?
Thx,
Joel
I just finished rebuilding my 1978 PCR; ZZ383, M22, etc. I had Allen's build a chambered system for the car connected to a set of McJacks headers... I'm getting popping out of the exhaust when I take my foot off the gas and am coasting.. Is this normal, or should I be looking for something which causes this?
Thx,
Joel
The usual cause is air getting in from a header flang gasket. I always use stock metal manifold gaskets on my headers. Also the collector gasket can cause this problem too and it doesn't take much of a leak, so you may not hear it but look for the black soot marks.
On really big diameter open pipes we've still had popping after everything is sealed up. At that point we had to adjust the carb and play with timing but some bikes, no matter what you do with a big exhaust they still popped every now and then rolling down hill.
Melting Slicks
Joined: Sep 2010
Posts: 2,413
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From: Emerald Isle NC
I have an Allen's chambered system and McJacks shorties also.
It does pop some. I just figured it was the nature of the chambered system. Checked my timing, vac. and plugs. It may be a little lean, but not much...
Carter
It does pop some. I just figured it was the nature of the chambered system. Checked my timing, vac. and plugs. It may be a little lean, but not much...
Carter
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Joel
Le Mans Master
Joined: Oct 2010
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
its pretty normal for a free flowing exhaust. a reverse flow muffler normally doesn't do it . glass packs and chambered systems do it a lot. nothing to be concerned about. mine does it and i don't mind a bit. LOUD PIPES SAVE LIVES , on my harley and my Vette.
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From: At my Bar drinking and wrenching in Lafayette Colorado
Popping in the exhaust on deceleration is caused by a lean condition, induced by the free flowing exhaust system. You need to richen up the carb to compensate for the headers and mufflers. This will eliminate the popping.
Lars
Lars
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By enriching I assume you mean idle mixture... When I have my foot off the gas (and it is popping), the throttle plates should be closed and we should be running on the idle circuit.... Is this correct?
Thanks!
Joel
Melting Slicks
Joined: Sep 2010
Posts: 2,413
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From: Emerald Isle NC
I checked/adjusted my idle mix for max vacuum. Still pops. This with a Quadrajet massaged by Lars.
My plugs looked a little lean (a light tan). Would like to fix it, but it won't be for long. 406 build is at machine shop...
Carter
My plugs looked a little lean (a light tan). Would like to fix it, but it won't be for long. 406 build is at machine shop...
Carter
Drifting
Joined: Dec 2004
Posts: 1,714
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From: Austin Texas
Might I suggest the next toy you get yourself be a wideband Air /Fuel gauge. I have found it to be much more helpful than a clock in my Corvette.
I recently converted my pipe size from stock to 2.5 in and installed straight through mufflers. On the way to the exhaust shop the a/f cruise reading was 13.5-13.7. On the way home it was 17.1 to -- . My little 600cfm on my 350 needed 4 jet sizes up and now the cruise is 14.2-14.7
All im saying is an a/f gauge is a valuable tuning tool to help you dial in each circuit of your carb. I use the AEM 30-4100 and put it in place of the clock. Its $175 to know what is going on.
I recently converted my pipe size from stock to 2.5 in and installed straight through mufflers. On the way to the exhaust shop the a/f cruise reading was 13.5-13.7. On the way home it was 17.1 to -- . My little 600cfm on my 350 needed 4 jet sizes up and now the cruise is 14.2-14.7
All im saying is an a/f gauge is a valuable tuning tool to help you dial in each circuit of your carb. I use the AEM 30-4100 and put it in place of the clock. Its $175 to know what is going on.
Last edited by johnt365; Feb 21, 2013 at 09:27 AM.
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Joined: Jan 2009
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From: New York
Might I suggest the next toy you get yourself be a wideband Air /Fuel gauge. I have found it to be much more helpful than a clock in my Corvette.
I recently converted my pipe size from stock to 2.5 in and installed straight through mufflers. On the way to the exhaust shop the a/f cruise reading was 13.5-13.7. On the way home it was 17.1 to -- . My little 600cfm on my 350 needed 4 jet sizes up and now the cruise is 14.2-14.7
All im saying is an a/f gauge is a valuable tuning tool to help you dial in each circuit of your carb. I use the AEM 30-4100 and put it in place of the clock. Its $175 to know what is going on.
I recently converted my pipe size from stock to 2.5 in and installed straight through mufflers. On the way to the exhaust shop the a/f cruise reading was 13.5-13.7. On the way home it was 17.1 to -- . My little 600cfm on my 350 needed 4 jet sizes up and now the cruise is 14.2-14.7
All im saying is an a/f gauge is a valuable tuning tool to help you dial in each circuit of your carb. I use the AEM 30-4100 and put it in place of the clock. Its $175 to know what is going on.
A mod ill do when I can get car to shop to weld in sensor