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Backfiring through the carb?
#1
I got the intake gasket replaced and made sure it doesn't leak.  I put new plug wires on and made sure they were routed to the proper cylinder.  The car idles good but has a miss and a backfire when I rev it up.  Where is the first place to start troubleshooting?  A friend said that a backfire is either timing or a vacuum leak.

Thanks!
Wade
1972 Mach 1 351 cj 4speed
"We confide in our strength, without boasting of it; we respect that of others, without fearing it."--Thomas Jefferson

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#2
Make sure the distributor is installed correctly, not a tooth or two off. Then re-check the spark plug wires to be sure you got the firing order correct. Then recheck the timing. Let us know when you get it sorted out. Chuck
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#3
A lean condition, caused by vacuum leak or carburetor, or timing are the most likely problem.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
[+] 1 user Likes Don C's post
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#4
(03-31-2019, 11:03 AM)c9zx Wrote: Make sure the distributor is installed correctly, not a tooth or two off. Then re-check the spark plug wires to be sure you got the firing order correct. Then recheck the timing. Let us know when you get it sorted out. Chuck

How would I tell if the distributor was a tooth or 2 off?  I checked the order of the wires again and they are correct.  Would not having the vacuum advance hooked up cause a backfire?  The port on the cap is plugged.

Thanks!
Wade
1972 Mach 1 351 cj 4speed
"We confide in our strength, without boasting of it; we respect that of others, without fearing it."--Thomas Jefferson

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#5
If your car idles okay and backfires when you demand more fuel sounds like your mixture needs a small tweak

Steve
1971 Grandé
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#6
With the #1 cylinder at top dead center, remove the the distributor cap and the rotor should be pointing at #1 plug wire.
And not having the distributor advance connected would cause a backfire, it’s something else.You can just keep that disconnected and plugged till you get the engine running right. Keep the the port on the carb plugged too.

run_horse Run Horse Run!
John 72 Q Code
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#7
Everyone is correct in what they are saying. I do not have one but the old shops had a smoke generator they could hook up and pump smoke into the vacuum lines to find any open places, split hoses and such. I could have got one cheap at auction last year and did not buy it.
The carb fuel pump on the front left has a lever with three pin locations. The pin should be in the center hole for average conditions. Going to the hole closest to the pump puts less fuel in and going toward the connection to the throttle increases I think. Might be backwards. You might try different positions there.
If you got to Mike's Carburetor parts he has some good video and info on how to tune it.
https://www.carburetor-parts.com/Trouble...p_623.html
Got to the link and look around he has several videos to watch also.


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
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#8
Hopefully you used a good brand of intake manifold gasket and not those printo leak gaskets.

run_horse Run Horse Run!
John 72 Q Code
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