backfire thru carb

[psgp]

i have been having this problem motor is a 468 bbc and have a 750 dp holley on it and i drag race it this problem happen when it wants its not consistant but off the line it backfires thru carb and was wandering what i should change or try to solve this any info would help thanks in advance

 

[GuysMonteSS]

If the distributor drive gear is worn it could cause the problem you are having.
Guy

 

[psgp]

its all brand new on dist. have 16 passes on motor and have had this problem since new hearing that i might be to lean

 

[khan0165]

backfires are caused by too advanced timing
(it can also be caused by too retarded timing, if you have an extreme cam)

if you've recently replaced the distributor, it's likely you put it in and were 1 tooth advanced on the timing gear.
... this means your timing is not right, and it is likely more advanced than you think it is.

I would start by looking at this, then adjust timing
you want to be around 12 to 16 deg at idle, depending on how radical your cam is

running lean will not cause backfires. If you fear you are running lean, check your plugs, the porcelain will appear dry and white. Ideal mixture, you want to see slight brown on the porcelain.

 

[bill]

backfires are caused by too advanced timing
(it can also be caused by too retarded timing, if you have an extreme cam)

if you've recently replaced the distributor, it's likely you put it in and were 1 tooth advanced on the timing gear.
... this means your timing is not right, and it is likely more advanced than you think it is.

I would start by looking at this, then adjust timing
you want to be around 12 to 16 deg at idle, depending on how radical your cam is

running lean will not cause backfires. If you fear you are running lean, check your plugs, the porcelain will appear dry and white. Ideal mixture, you want to see slight brown on the porcelain.

X-infinity

 

[pontiacgp]

if it's inconsistent it doesn't sound like timing to me , I'd be looking at cross induction in the wires so I'd be separating them. I run my wires under the header and have the wires set up like this on the cap. I find the wires don't cross as much and are easier to keep separate.

 

[psgp]

thanks guys i just found out that i have 2 diffrent motor mounts so drivers side sits higher gonna change that tommorow so it sits right could that have anything to do with it??? and i have my wires in a wire loom and have them seperatd as much as possible my timing is at 38 total when it dont backfire is a consistant car

 

[woody31]

i would look at the intake valves...how tight are the guides,, sounds like a intake valve is sticking open.....
dont hit the spray till u fix this issue or you will be building another one.....

 

[psgp]

not running spray just motor this a a rebuilt motor and have had this problem since its been built heads were redone thanks for all the info

 

[woody31]

check your guides,,,lifters,,,,maybe a weak or broken inner spring or damper

you wont see a broke inner srping so ,,,,take your chances or start the tear down
either way its gonna be a lil $$$ now or ALOT later 8)