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Author Topic:   miss fire
logger226
Dirt Roller

Total posts: 11
posted June 04, 2002 07:27 AM
my car misfires half way down the straits with a 650 holley on it.but when i take it off and run q-jet it runs fine.could this be to much fuel or bad distubuter? i've been down jetting the holley every week and it seems to be getting better but i'm just wondering if i'm looking at the wrong thing meaning elictric not fuel

smayo964
Dirt Forum Racer

Total posts: 90
posted June 04, 2002 07:37 AM
Hey Logger. There are a couple things you can look at, valve springs, power valve, and ignition. I chased a miss for several weeks in my street stock until I finally realized I had some bad springs (floating). I had already replaced wires, plugs, pickup coil, etc. On the other side of the coin, I had a power valve go out on my truck and it acted the same way on the street. Hope this helps.

logger226
Dirt Roller

Total posts: 11
posted June 04, 2002 07:45 AM
quote:
Originally posted by smayo964:
Hey Logger. There are a couple things you can look at, valve springs, power valve, and ignition. I chased a miss for several weeks in my street stock until I finally realized I had some bad springs (floating). I had already replaced wires, plugs, pickup coil, etc. On the other side of the coin, I had a power valve go out on my truck and it acted the same way on the street. Hope this helps.

i really can't see it being springs. why would it run fine when i change carbs?

smayo964
Dirt Forum Racer

Total posts: 90
posted June 04, 2002 07:54 AM
Unless you have flow tested both carbs back to back, they are probably flowing different. One (Holley) could be richer than the other, letting more unburn fuel enter the exhaust and detonate with a floating spring. Just offered the spring condition to consider. You might want to look at the power valve then on your Holley. Also, how high is your float set? Could be pulling excess fuel by pressurizing fuel past the needle at high RPM. Just some areas to consider.

dirtbuster
Dirt Freak

Total posts: 353
posted June 04, 2002 02:40 PM
Do you run an alternator?

We had a little different situation in our mod but it had a vibration down the straightaway and we chased it for 4 weeks from balancing driveshaft and checking for loose bolts, fan blades, etc. to pulling plugs and rejetting carb.
Turns out our battery was bad and was not getting enough voltage to the ignition causing a misfire at higher rpm's hence the vibration. Changed batteries and it was totally different motor. Lot more power.

A little different than your situation since changing carbs fixed it but still something to think about.

merlinmech
Dirt Full Roller

Total posts: 51
posted June 05, 2002 09:02 AM
Smayo is right, it's probably too rich. Try a different power valve first (one that opens with less vacume).

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