backfire through the carbs ..., makes for nice fireworks! |
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backfire through the carbs ..., makes for nice fireworks! |
SirAndy |
Jan 30 2005, 01:18 AM
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#1
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Resident German Group: Admin Posts: 41,675 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
hey, it's me again, the "carb-hater" !!! (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
i've been trying to get this engine to run right for what now, 10 months??? (IMG:http://www.914world.com/bbs2/html/emoticons/headbang.gif) i still have a issue with backfires upwards through the carbs (looks cool at night with the GT-engine lid) !!! now here's my question: - i'm still running stock (well, SSI) heat-exchangers and a close to stock (Manta) exhaust. - i have a cam with a lot of overlap. could the stock(ish) exhaust setup cause too much backpressure and the engine doesn't flow and belches back through the carbs ???? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif) Andy PS: this happens all over the rpm range, but more often under lower rpm load and higher rpm "cruise" (steady gas) and only sporadically at WOT ... |
jwalters |
Jan 30 2005, 06:45 PM
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#2
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Sooo Close....... Group: Members Posts: 1,677 Joined: 14-May 04 From: Huntsville, AL Member No.: 2,068 Region Association: Europe |
So it would be safe to assume you do not know the cam profile?? Maybe the lobes were ground with an unusually tight centerline---I was looking back thru your post--WOT the same thing?? What rpm are you maxing it to?
If these are not it--it might be a bad grinding on the valve seat or the face, know what I mean---not a burned valve, just not seating right due to the stone used being to worn when it was ground--I have come across this once....it was a 350 chev motor from chev!! in a truck---when it heated up it became very evident by blowing smoke out the tailpipe--different from what you are describing--but when this pup let go--lets just say I brought ALL traffic to a stop, it was like a mosquito fogger going by, times a hundred!!---that was the only vehicle I have ever been embarrased to be seen in! The cops tried to pull me over, I knew they were back there, but I was hell bent on making it back to my shop from the test drive--they found me by following the smoke trail--they could only go 2 mph behind me and could not catch me--but because there was no wrecks they laughed it up and let it go----whew!!! I know this is making you tense--but from my experience, it is a two dollar part / process doing it----I hope you find it w/o pulling the motor apart-- |
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