What causes carbon in intake runners and carb?
#1263229
07/06/12 09:26 PM
07/06/12 09:26 PM
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Joined: Jan 2003
Posts: 4,269
Morrow, OH
markz528
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Posts: 4,269
Morrow, OH
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I'm assuming it is carbon, but it might not be. What causes the black (carbon?) in intake runners and in a carb?
Ran a 750 Holley vacuum secondary carb maybe 10 to 20 hours last year on my daughter's 67 coronet with a 383. Was freshly rebuilt when I installed it. The carb is now heavy black.
My cousin's 400 cid 67 Firebird with a Paxton supercharger has half the runners black and half clean. Its a dual plane that we now know is a mistake. The cylinders that are rich have the black runners.
What is causing this?
67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......
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Re: What causes carbon in intake runners and carb?
[Re: OUTLAWD]
#1263233
07/07/12 12:22 AM
07/07/12 12:22 AM
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Joined: Jul 2006
Posts: 395
campbell river B.C
mopartoby
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enthusiast
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Posts: 395
campbell river B.C
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Quote:
[/Reversion. Wrong cam, carb, intake, heads, pistons, etc, etc, etc... Whatever combination you have isn't matched very well and isn't working to it's best capabilities. It may run great, (in your mind), but sounds like it has a very long ways to go to be tuned to it's fullest potential. Good luck quote] :
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Too much overlap
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Re: What causes carbon in intake runners and carb?
[Re: 8urvette]
#1263238
07/07/12 11:22 PM
07/07/12 11:22 PM
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Joined: Jan 2003
Posts: 4,269
Morrow, OH
markz528
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Morrow, OH
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To answer some of the questions, the Coronet did have a working PVC and the breather fed into the air cleaner. Both engines run on pump gas.
The 383 internal condition is not known, but given all the leaks and other mechanical work on the car, it probably stinks. The car now has a fresh 440 in it. Have not done any tuning to it yet. Timing is 14/35 - both engines.
As far as my cousin's Pontiac 400, I do buy reversion, but why only on 4 cylinders? What does the blower have to do with it? We do know that we did have too much retard in it. It was probably high teens at full boost.
67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......
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Re: What causes carbon in intake runners and carb?
[Re: markz528]
#1263239
07/08/12 12:11 AM
07/08/12 12:11 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
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Master
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Posts: 52,972
Romeo MI
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Quote:
I'm assuming it is carbon, but it might not be. What causes the black (carbon?) in intake runners and in a carb?
Ran a 750 Holley vacuum secondary carb maybe 10 to 20 hours last year on my daughter's 67 coronet with a 383. Was freshly rebuilt when I installed it. The carb is now heavy black.
My cousin's 400 cid 67 Firebird with a Paxton supercharger has half the runners black and half clean. Its a dual plane that we now know is a mistake. The cylinders that are rich have the black runners.
What is causing this?
The Pontiac just has the wrong cam in it... any pressurized
engine doesnt like over lap on the cam... as to your
other car what did you put in for a cam and did you
degree it... did you do a valve job on it
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Re: What causes carbon in intake runners and carb?
[Re: 10.90 Racer]
#1263242
07/08/12 11:24 AM
07/08/12 11:24 AM
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Joined: Mar 2007
Posts: 3,300
Northern Indiana
Dunnuck Racing
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master
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Northern Indiana
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Camshaft design (valve event timing),valve jobs,and header efficiency all can affect it. You can have a ton of overlap and never see signs of reversion if everything else is right. I am finishing up testing 12 different camshafts in one of my engines,one of them had signs of reversion in the intake runners. It was the one with the least overlap of all the cams tested. It has a lot to do with the rest of the valve timing.  Keith
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Re: What causes carbon in intake runners and carb?
[Re: S/ST 3040]
#1263244
07/08/12 11:54 AM
07/08/12 11:54 AM
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Joined: Mar 2007
Posts: 3,300
Northern Indiana
Dunnuck Racing
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master
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Northern Indiana
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Vic, I think a lot of it has to do with the valve job/port design you do. Flowing good the right direction without flowing good the wrong direction. But then that is probably easier said than done?  Even with 104 degrees of overlap @.020 and too small of a header,no signs of reversion on the 421. It took too small of a camshaft with very little overlap(too wide of a lsa) and late exhaust timing to show any signs of reversion. Keith
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