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+--- Thread: exhaust backfire? (/thread-2268.html)
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exhaust backfire? - abunchofidiots - 07-15-2010
firefighter2134 Wrote:if you have a vacuum guage hook it up to timing advance port on carb and set it to the guage. that should set your mixture right.
I thought you were suppose to hook it up to manifold vacuum and disconnect/plug the timing advance going to the distributor...
exhaust backfire? - bucketobolts - 07-15-2010
Sounds like the vacuum port is ported vacuum. It will not have any vacuum at idle, but as the RPMs increase and the throttle plate opens the vacuum will be applied. If your getting too rich of an idle you may try using manifold vacuum. That will give you more advance at idle to help burn the extra fuel. But still set your base time with the advance disconnected.
As for the backfire, I don't believe the idle circuit would be causing your problem. The intermediate/cruise circuit sounds a bit fat. Have you tried changing the primary jets? You can get this mixture close with the jets, then fine tune with the power valve.
The backfire will also be aggravated by any type of exhaust leak. Fuel and burned exhaust won't burn. But let a little fresh air seep in and pow!
exhaust backfire? - berg bronco - 07-15-2010
bucketobolts Wrote:Sounds like the vacuum port is ported vacuum. It will not have any vacuum at idle, but as the RPMs increase and the throttle plate opens the vacuum will be applied. If your getting too rich of an idle you may try using manifold vacuum. That will give you more advance at idle to help burn the extra fuel. But still set your base time with the advance disconnected.
As for the backfire, I don't believe the idle circuit would be causing your problem. The intermediate/cruise circuit sounds a bit fat. Have you tried changing the primary jets? You can get this mixture close with the jets, then fine tune with the power valve.
The backfire will also be aggravated by any type of exhaust leak. Fuel and burned exhaust won't burn. But let a little fresh air seep in and pow!
I dont want to change jets if i dont have to I do have some very small exhaust leaks ill try to patch. I bought a vacuum guage today so ill give that a shot thanks for everybodys help ill let you know what happens
exhaust backfire? - berg bronco - 07-15-2010
ok I checked the vacuum its at 14 with a very small shake I read that if your motor is higher performanca motor that this reading is right all my motor is bored out 0.30 and has a rv cam and im also at 2500 elev. is it reading right or should it be a liitle higher? i also sprayed some carb cleaner aourn the carb base and intake and the motor sounds the same. and timing is right
exhaust backfire? - firefighter2134 - 07-15-2010
i just got my 302 running and ending up with almost 18 degrees advance timing. which i thought was a little above normal but runs great. try to advance your timing a little..loosen distributor hold down screw just enough where you can turn distributor and turn clockwise. do this with engine running and timing light. just dont move it too much to begin with and make sure it takes fuel when you hit throttle.
exhaust backfire? - berg bronco - 07-15-2010
firefighter2134 Wrote:i just got my 302 running and ending up with almost 18 degrees advance timing. which i thought was a little above normal but runs great. try to advance your timing a little..loosen distributor hold down screw just enough where you can turn distributor and turn clockwise. do this with engine running and timing light. just dont move it too much to begin with and make sure it takes fuel when you hit throttle.
ill try that ive noticed know that after idling for a few minutes the carb starts loading up and then it stalls only way to keep it runing is step on the gas a little then clears up and then after a few minutes it does the same thing,
why?
exhaust backfire? - firefighter2134 - 07-15-2010
did you buy the carb new or used? that may be caused by float level. as far as advancing your timing start with about 6 to 8 degrees..then go from there. just get it up to operating temp before starting.
exhaust backfire? - berg bronco - 07-15-2010
new holley carb . I advanced the timing a little and it seamed to run better
exhaust backfire? - firefighter2134 - 07-15-2010
just keep vacuum guage on carb while you advance it and burp throttle to make sure it will take the fuel if you romp on it.after you get it set where you want it tighten up dis screw and adjust idle to your preference. glad i could help. im ready to run mine to see what it will do
exhaust backfire? - berg bronco - 07-15-2010
thanks for the help!