429 backfire through carb
#1
429 backfire through carb
Hi everybody
I have a 429 with a 4300 carb and when I try to rev it up it backfires through the carb and if I'm driving it and try to get on it, it backfires and loses power
Yesterday I advanced the timing and revved it up and it didn't do it anymore so I took it on a short drive and everything seemed good
Now today it is doing it again, I tried to advance the timing a tad more but it didn't help
I also put in a new accelerator pump but no help
I took the air cleaner off and pumped the throttle lever by hand and it seems like the accelerator pump is only giving one decent squirt and then the next time I pump it, it barely squirts any gas out
Thanks for any help
I have a 429 with a 4300 carb and when I try to rev it up it backfires through the carb and if I'm driving it and try to get on it, it backfires and loses power
Yesterday I advanced the timing and revved it up and it didn't do it anymore so I took it on a short drive and everything seemed good
Now today it is doing it again, I tried to advance the timing a tad more but it didn't help
I also put in a new accelerator pump but no help
I took the air cleaner off and pumped the throttle lever by hand and it seems like the accelerator pump is only giving one decent squirt and then the next time I pump it, it barely squirts any gas out
Thanks for any help
#3
#4
If so...then sounds like you proably got some dirt in the carb plugging things up. The pump pushes fuel through small passages within the carb that can plug up quickly if you have dirt in there.
#5
#6
Not entirely sure what you mean but lack of power under load can be many things from fuel to valve and/or ignition timing...amont others.
Is it a continuous lack of power or only initially when you try to accelerate?
The fuel system, carb especially, can not function properly for various reasons. The carb needs to be functioning properly on all aspects to realize the total porformance.
Check the basics:
Are you getting a good fuel supply to the carb? Proper flow and pressure. i.e. is there a pump and/or filter issue
Are the float levels adjusted properly to maintain proper bowl level?
Check choke operation to make sure it's opening all the way when the engine is warmed up
Is the carb clean and not plugged anywhere? If you have dirt in there it will block passages including the primary jets.
Check your initial and total ignition timing. If the initial timing is not set properly and not advancing correctly...that can cause an engine to run weak. Make sure your vacuum advance is connected to the proper source. Should be a vacuum source on the carb that only sees vacuum after the throttle is open. sometimes called "spark" or "idle" vacuum.
Check your manifold vacuum at idle...that can tell you a lot on how your engine is running.
btw...what carb do you have?
#7
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#8
That is also a symptom of a camshaft lobe(intake lobe) going flat.If the carb suggestions don't solve your issue,you might want to pull the valve covers and watch the rockers as someone turns over the engine(without starting it as this can be messy).If a lobe is flat it should be apparent as the culprit will not rise as much as the rest do.I hope it's not the cam but it does happen.
#9
OMG!
What can I say... yesterday I had 10 minutes and I checked here and there and just before unmounting the carb and the distibutor I checked the firing order ( a third time) again ...
It's hard to say it but ... I messed it up
should be 15426378 was 15423678
Will test the engine today... think thats the issue
Thanks for your help
What can I say... yesterday I had 10 minutes and I checked here and there and just before unmounting the carb and the distibutor I checked the firing order ( a third time) again ...
It's hard to say it but ... I messed it up
should be 15426378 was 15423678
Will test the engine today... think thats the issue
Thanks for your help
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