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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Oct 2006 Posts: 11 New Guy | | New Guy Joined: Oct 2006 Posts: 11 | riley
235 backfiring through exhaust any suggestions? | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 |
Bill Burmeister
| | | | | Joined: Oct 2006 Posts: 11 New Guy | | New Guy Joined: Oct 2006 Posts: 11 | riley
Thanks for advice. How about adj. valves. | | | | | Joined: Jan 2000 Posts: 2,074 'Bolter | | 'Bolter Joined: Jan 2000 Posts: 2,074 | I'm with LONGBOX55, timing but adj the valves wouldn't hurt. | | | | | Joined: Oct 2006 Posts: 11 New Guy | | New Guy Joined: Oct 2006 Posts: 11 | | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | I was also going to suggest going through the valves as well. I had a similar problem with mine, and doing the valves didn't help too much, but resetting the timing took care of the rpolem.
Bill Burmeister
| | | | | Joined: Oct 2003 Posts: 445 Shop Shark | | Shop Shark Joined: Oct 2003 Posts: 445 | check conpression.this will tell you where the troble is.SOUNDS like a burnt exhust valve.maybe a bent push rod or adjustment.something else maybe a condenser in the distributor
dan-pa
| | | | | Joined: Mar 2005 Posts: 637 Shop Shark | | Shop Shark Joined: Mar 2005 Posts: 637 | If the backfiring is on slowing down, the carburetor is lean, opening the idle screw a little will stop that. | | | | | Joined: Apr 2005 Posts: 1,971 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,971 | Start at the beginning of things.
Pull your plugs and not the colors. Note which plug goes to which cylinder. Get a spark plug color chart out and match them up the best you can with the pictures. Are they all too dark? than its too rich. Are they all light colored then it's too lean. Is there black sludge on one side of the plug? Most likely oil leaking past a valve. etc. etc. Is one plug mcuh different in color thatn the others? That cylinder is most likely the problem.
Do a compression test. Are all the cylinders pretty close in compression, or is one way off?
Do a leak down to determine if there is a leak through a valve. etc. then check the valve adjustment on the one in question to see if that solves the problem. You may get the valve adjusted just right and make a bad adjustment on another creating the same (or different) problem elswhere.
Don't jump around guessing. Check the easy things first and draw a conclusion from your findings.
When you say "backfire" is a loud bang like a firecracker, or a rumbling popping? If it is the rumbling popping when you let off the gas, my next question is "Do you have glass packs or a real muffler?" | | | | | Joined: Oct 2006 Posts: 11 New Guy | | New Guy Joined: Oct 2006 Posts: 11 | Riley
The popping occurs in neutral while reving engine, haven,t had a chance to drive truck. Truck has real mufflers. | | | | | Joined: Oct 2006 Posts: 11 New Guy | | New Guy Joined: Oct 2006 Posts: 11 | Riley
The popping occurs while reving motor in neutral, haven,t had a chance to drive it . | | | | | Joined: Apr 2005 Posts: 1,971 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,971 | Tell us your findings with the spark plugs and compression test. | | |
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