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  #1  
Old 06-03-2007, 07:09 AM
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grand_wag_85 grand_wag_85 is offline
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Backfiring thru the carb

For whatever reason my J10 keeps backfiring thru the carb. It's got a 258 and had a cam installed not too long ago. I loosened up the dizzy and spun that arround a bit while running to cut down on the backfiring, then I set it to the correct firing order and it's ALOT better but still backfiring thru the carb at high RPM's and when revved.

According to my Chilton's manual it's got the Holley 4350 carb that's supposed to go on a 401 Probably a typo...

Vacuum advance is working fine, all vac ports on the carb look good. What am I missing?
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  #2  
Old 06-03-2007, 07:46 AM
Ristow Ristow is offline
 
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through the carb's usually a lean condition.
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  #3  
Old 06-03-2007, 08:00 AM
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Gotcha, tried adjusting the screws but that didn't seem to help either...There's alot of black, wet sooty stuff out of the exhaust.
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  #4  
Old 06-03-2007, 08:25 AM
Ristow Ristow is offline
 
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hmm. well,it can be be other issues as well.

however-the screws are for idle mixture only,popping through the carb is usually from incorrect jetting,or a faulty enrichment system,as it pops when you get on the throttle.
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Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

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  #5  
Old 06-03-2007, 08:33 AM
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Gotcha...So how would one go about checking/determining the proper jetting?
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  #6  
Old 06-03-2007, 08:39 AM
Ristow Ristow is offline
 
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the jetting should be fine,since it's a stock setup.

you'llo be looking for problems in the carb.you have the bbd carb?

could be ignition,but ignition problems are usually backfiring through the exhaust.
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Ristows right.................again,




Quote:
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... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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  #7  
Old 06-03-2007, 08:47 AM
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fulsizjeep fulsizjeep is offline
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<ramble>

A 4350 is a big honkin spread bore carb for 401 and 360. The big Lincolns of the era ran them on 460s too. So, you don't have that. If I ever put a 4 bbl on a 258 it sure wouldn't be a 4350. I had an 81 J10 set up like yours once. After I had it several months, it gave me fits with fuel delivery and back firing through the carb. Forget what type the early 80s 258 carburators are, but I rebuilt it first, reset the timing and it got better, but there were more problems like poor idle and rough at low rpm. It finally left me stranded on the beach in the fog hunting for 3 lost golden retrievers. I was so miffed, I just ripped all the vacuum hoses off except for the dizzy to carb connection, plugged some ports and disabled all the emissions. It ran great for the next several years. A friend of mine that worked for Chevron out on the island brought the dogs home the next day.

</ramble>
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Last edited by fulsizjeep : 06-03-2007 at 08:49 AM.
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  #8  
Old 06-03-2007, 09:15 AM
Ristow Ristow is offline
 
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'82 would have the carter bbd.
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Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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  #9  
Old 06-03-2007, 10:03 AM
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Chilton typo Kinda figured they had it wrong anyways
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  #10  
Old 06-03-2007, 05:06 PM
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crossed plug wires/dist cap / flat cam/fouled plug
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  #11  
Old 06-03-2007, 07:36 PM
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Quote:
Originally Posted by Ristow
through the carb's usually a lean condition.


popping is one thing, backfiring is another. Back firing is due to having timing incorrect (plug wire one off on the dizzy, timing set wrong, jumped timing chain, etc.) as the plug fires while the intake valve is still slightly open, thus allowing the explosion to continue up the intake runners and through the carb. Are you sure it was backfiring, or did you hear a sound and assume it was?
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  #12  
Old 06-03-2007, 08:08 PM
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Well it pops BADLY at high RPM's or when revving, w/o the air cleaner on you can see puffs of smoke or vapor out of the carb.
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  #13  
Old 06-03-2007, 08:11 PM
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I agree with billyrb could me a stuck valve.
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  #14  
Old 06-03-2007, 08:31 PM
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Has it been happening only since the cam was installed or did it happen before? Wondering if you are off a tooth on the timing.
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  #15  
Old 06-03-2007, 08:39 PM
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I bought a 79 ford 4x4 with a 302 a couple of weeks a go. It had jumped time. anytime I could get it to fire it would fire back through the carb.
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  #16  
Old 06-03-2007, 08:51 PM
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The condition will worsen when the engine is revved up since the timing curve kicks in with the vacuum advance.
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  #17  
Old 06-03-2007, 09:28 PM
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The cam was installed just before I got it back in like '05 or early '06 I want to say and the problem has only started within the last few months.
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  #18  
Old 06-04-2007, 06:08 AM
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what is your current timing set at?
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