Back fires through exhaust

MoabCJ8

Basic User
City
Lehi
State
Ut
#1
Having an issue I cant seem to figure out. Jeep runs and drives perfect but if you rev up the motor and let off quick it will back fire through the exhaust. I have replaced the intake/exhaust manifold gasket thinking that was it but it made no difference.
I tried disconnecting the plugs one at a time to see if a certain cylinder was doing it and it did it not matter which one I disconnected.
It is a rebuilt 258 with the original Carter carb. Everything looks tight and perfect.

Possible things I have been thinking of:
-Carb adjustment
-Spark plug.
-Low octane fuel

Any ideas or first hand knowledge of this problem?
 

skiptown

CJ-8 Member
CJ-8.com Member
SOA Member
City
Madison
State
WI
#3
Did this just start or have you "done" something to the engin recently
 

MoabCJ8

Basic User
City
Lehi
State
Ut
#5
I purchased the Jeep about a month or so ago and have been restoring/building it.
Haven't driven it more then a mile so far but this is one of its little quirks that are bugging me.
 

Rosco1974

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
West Haven
State
UT
#6
Timing? What is it set @ and was it checked warm with vacuum advance blocked off?
 

b.b.chev

Legacy Registered User
City
Black Forest
State
CO
#8
Does it still have the air pump hooked up ? When I was a car mechanic I used to run into bad diverter valves causing this problem .
 

Kim Dawson

CJ-8 Member
CJ-8.com Member
City
Molalla
State
Or
#11
Might do a compression check and make sure a valve stem isn't bent or something holding a valve open.
 
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