Ok so i have a chevy 350 with a set of headers and a quadrajet carb. The motor wont stay running and bucks and backfires out the carb. or shoots a flame out the carb. I changed the carb to another one i know works off another 350 i have and the same problem. so its not the carb. I have played with the distrib and no luck. i had a friend look at it and he seemed to think it may need new plugs,wires,buttom and cap. when the motor dose get started it seems to run just dosent idle. so im not sure if its the timing. any pointers would be good!!! would wires and plugs make it buck and backfire out the carb???
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Hey Boys chev350 Q???????
- Thread starter looloozu
- Start date
trailblazr81
1/2 ton status
Check you timing, and make sure your wires are connected good and you have the firing order correct. Is this something that just started happening for no apperent reason?? Is this a rebuild or motor swap? What have you done to this engine? Did you just happen along a crappy running motor?
its been a good working motor never any probs. its been in the same truck for a year or so. it sat for a few weeks over the summer when i installed a liftkit. before that it ran great. it just seemed to have problems running one day and overnight it started this stuff. would bad plugs and wires back it backfire like that?
K5dreamer
1/2 ton status
the only time ive ever seen an engine backfire out through the throttle body or carb was with the distributor 180 degrees out of time.
its weird that this started after a lift kit install, or with the truck just sitting.
one thing to check is get a can of gumout arosol (sp) spray degreaser, and start the truck by spraying that into the carb, and keep spraying to see how the truck idles, then stop spraying and see if the truck bucks and dies.
depending on how long the truck sat, the fuel could have varnished and pluged up some venturi or something. i suppose its possible that a lean condition could cause a backfire, but its most likely the timing.
if you would like a run down on how to set the timing id be happy to give it a shot over the internet. also if you can, review how to set your idle speed screws and jets on the carb. thats something im not fully up to speed on but im sure someone here can help ya out.
its weird that this started after a lift kit install, or with the truck just sitting.
one thing to check is get a can of gumout arosol (sp) spray degreaser, and start the truck by spraying that into the carb, and keep spraying to see how the truck idles, then stop spraying and see if the truck bucks and dies.
depending on how long the truck sat, the fuel could have varnished and pluged up some venturi or something. i suppose its possible that a lean condition could cause a backfire, but its most likely the timing.
if you would like a run down on how to set the timing id be happy to give it a shot over the internet. also if you can, review how to set your idle speed screws and jets on the carb. thats something im not fully up to speed on but im sure someone here can help ya out.
K5dreamer
1/2 ton status
oh and another thing it might be, the distributor control module, its a small peice located under the rotor. its an annoying little bugger that can cause all kinds of driveability problems that confused the hell out of people. its only like 50 bucks. so it might be worth replacing just as a check 
beater_k20
Banned
do a compression and leakdown test while you're at it, see what kind of condition the motor is really in.
ok so check the
timing
compression test
plugs and wires
rotor but and cap
anyone think of any other stuff to test. remeber this carb just came off a working 350 less then 20min before it went on this motor. so i know it works fine.
timing
compression test
plugs and wires
rotor but and cap
anyone think of any other stuff to test. remeber this carb just came off a working 350 less then 20min before it went on this motor. so i know it works fine.
beater_k20
Banned
but it doesnt sound like a carburetor problem... would you check your battery if your tires were going flat?
looloozu said:
^^Check these and get back to us
K5dreamer
1/2 ton status
well..... actually, swapping a working carb from another engine wont always work, the carb settings may be different depending on engine size, cam, head flow, fuel demands.... etc. etc. but if its still doing the EXACT same thing, and the engines are pretty similar as far as cam specs and size and whatnot, then yeah you can probly ignore the carb as the cause.
trailblazr81
1/2 ton status
vacuum leaks can be a biatch.
Add that to the check list.
Add that to the check list.ok so i got a new set of plugs and wires. new rotor cap and button. still no luck. BUT i turned the distrib all the way counter clockwise. I think thats advansing it. and she starts and seems to run no backfireing out the carb. its still fussy but alot better. it seems if i could turn the distrib just alittle more it will be good. Is that mean maybe i jumped a tooth or something???
trailblazr81
1/2 ton status
Did you ever remove the distributor. It shouldnt jump a tooth all on its own.
pauly383
Daddy383
Stretched timing chain , or wore out factory plastic coated cam gear could make the symptoms too .
trailblazr81
1/2 ton status
looloozu said:
Ok do this as a test. Move your plug wires over one terminal on the cap in the same way you were turning it that got it running better. This will be the same as turning the dizzy. You may then have to turn back the dizzy because of how much this is moving the advance/retard. If you do this and can turn the distributor and get it run good then thats a start. Then we look into cam gear problems or timing chain stretching or jumping a tooth.
K5dreamer
1/2 ton status
im still of a mind that somehow, someone moved that distributor, my IROC had 23 degrees of slack in the timing chain, and still ran just fine. the only time ive seen fireballs like that coming out the throttle body or carb was with the dizzy 180 out, or the wires being crossed on the distributor control module. ive youve turned the dizzy as far as you can and its better but still not running great, then somewhere, somehow someone moved that dizzy and it needs to be reset to the number one cylender at top dead center.
trailblazr81
1/2 ton status
Ive had fireballs shoot out of carb when trying to start and my timing and carb adjustments are fine. Truck had been sitting for a while and didnt want to start. Cranked, stuttered, tried to start and 
out carb. Good thing I had air cleaner off.
out carb. Good thing I had air cleaner off.
