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exhaust backfire

2K views 10 replies 6 participants last post by  josh schaad 
#1 ·
68 327-had engine trouble for awhile now. sometimes runs great sometimes stumbles under load. just started having exhaust backfire and think its related. did a tune up points,cap,rotor,etc didnt fix the problem. just put new world heads on 6 months ago so i hope it isnt a head problem. the header on the backfire side was sort of loose when i checked it recently so i have a feeling. could it be the distributor? its pretty old (original). definately not the carb (some problem with different carbs). note, 2400 stall speed installed around the same time as the problems started.

[This message has been edited by josh schaad (edited 08-21-2000).]
 
#3 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by 427TRI:
Josh, did your tuneup include new wires?<HR></BLOCKQUOTE>

yes, ive changed about everything thats cheap in the effort-cap, rotor, points-dwell at 32, wires, plugs, fuel filter, fuel pump, retorqued the intake, checked the vacuum lines for cracks and the timing checks out.
 
#5 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by CA420:
Are you 180 degrees out or off one wire? Maybe you put #1 on #8 then started around the distributor? Crossed wires?

<HR></BLOCKQUOTE>
i will double check the order however the tune up was done several months ago and the car has ran good on occasions since then (but for the recent exhaust backfire which is continual during idle and accelleration).
 
#7 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by CarlC:
josh,

At what throttle condition does the backfire occur?

<HR></BLOCKQUOTE>it occurs continually from idle to accelleration. when i got pissed and slammed it to the floor it seem to go away until i let off.
 
#8 ·
Josh, if you have access to another distributor you can borrow for an hour, try that. Your distributor might have just gotten worn enough to start scattering spark. But truly I am at a loss.

Since I run a solid cam motor, if I have some unusual problem, I always begin my tunbeup with checking valve lash.

It doesn;t sound like a carb problem, but....



You just have to start at square one and start eliminating variables. Check the valves. See if one is loose, possibly indicating a worn cam lobe.

FWIW I have horsed on new wires during installation and broke the cores before. You might want to take a VOM to the wires to make sure they have continutity.

In this type of diagnostic, I have learned to NOT ASSUME ANYTHING. check everything, new or not. You will find the problem.

------------------
Gene C.
67 Chevelle SS 427/L88

[This message has been edited by 427TRI (edited 08-22-2000).]

[This message has been edited by 427TRI (edited 08-22-2000).]
 
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