429 Sneeze/backfire???
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Tuned
Joined: Jun 2008
Posts: 253
Likes: 4
429 Sneeze/backfire???
I have a 429, very mild build, almost stock. Just finished a resto and am now tuning the truck for the street. I can not get it to run good, it idles nice, but it has no power at all. I also can not get it to stop sneezing, sputtering, backfiring through the carb when giving it heavy throttle. I tried tuning the timing from 0 degrees to around 25 btc, currently around 10-15, tried the vac advance but dont know what im doing tuning in there. Had a holley 750, switched for a edelbrock 600, both did nothing. Have not found any vac issues, running out of ideas. Thinkin screw the old tech, moving towards using a 12 valve cummins. Any ideas???
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Tuned
Joined: Jun 2008
Posts: 253
Likes: 4
Its actually a brand new dist/cap/rotor. I do think I will be pulling the timing cover off to inspect the timing chain/timing marks. But I may try a different distributor first as I have 2 460s on the shop floor that run that I can pull the dist out of.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Ported vacuum nipple should have "NO" vacuum at idle. If the timing changes between the hose being connect and not, then you are on the manifold vacuum nipple and no the ported vacuun nipple.
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Tuned
Joined: Jun 2008
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Oh? well I am on a edelbrock 600 carb, with a fitting on the drivers side/ pass side of the FRONT of the carb. What one to use???
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Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
But if the nipple for the ported vacuum has vacuum on it at idle the carb is adjusted wrong.
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