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Author Topic:   Rochester 2 barrel
Dirt Roller

Total posts: 14
posted May 24, 2002 06:04 PM
I was trying to fix my exhaust and had to remove the exhaust manifold i placed the sparkplugs and wires on top of the motor above the plug holes and never checked to make sure they were right when re-installing them i got 2 plug wires crossed and it poped really bad for about 30 seconds before i shut it off (i know a really stupid mistake) my question is could this of messed up the carb? it runs great my concern is only for a loss of vacume. could this be in the carb/ the heads or the piston rings? any suggestions would be great. i pulled the valve covers and started it there's no noticable difference between movement.

Dirt Freak

Total posts: 408
posted May 24, 2002 08:54 PM
While backfiring thru the carb can hurt a Holley power valve immediately, it will not do much to the Rochester carb, other than crush the brass float (if there is one in there.
Extreme cases, I would imagine, could blow out a gasket either internally, or in a way that could cause a vacuum leak (which I think is what you may be describing).

To pinpoint it, tho, I'd need a bit more info on exactly what the carb is doing now.

It also could be other things, such as intake gasket leakage, improper lifter adjustment, etc.

If we can help in any way, just shout.

Hope ya find it.


Dirt Roller

Total posts: 14
posted May 25, 2002 10:33 AM
There appears to be nothing wrong with the carb. I ran it last night and it was awesome (except driver error LOL). I've read replies about the holley and how a backfire can hurt them. If i didn't have a vacume rule i wouldn't know there was anything wrong. All my mechanic buddies say it running too good to rebuild it. their suggesting i do a compression leakdown check. so iguess i'll borrow a gauge and perform that. I'll let you know what i find.

Dirt Roller

Total posts: 14
posted May 27, 2002 12:52 AM
I just finished a compression check and all cylinders were between 85 and 95 except #7 which only had 60 LBS I squirted some oil in the cylinder and no change to compression.I know i need to re-ring the motor we planned on it in the off season last year however it just never got done. My question is with no change the compression in that cylinder could i have a bad valve. we will be tearing the motor down but due to other commitments i can only race 4 more times this season is the possibility of a bad valve enough to look into or should i drive it.

Dirt Full Roller

Total posts: 51
posted May 27, 2002 09:25 AM
If you put oil in the cyl. and no change, probably a bad valve. Either way you're looking at a teardown. Just as well rering at the same time. Get a leakdown tester. That will tell you exactly where the problem is.

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