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77 Nova....Backfireing out of Carburator...NEED HELP


Novagirl
05-04-2004, 02:08 PM
Need some help:

I have a 77 Chevy Nova, and I am having the problem that when you start...will run, and sound great, but if you rev the engine or try to put in gear and even drive...it is backfiring through the Carb. We are stumped.

Here is what has been done:

new heads, distrubutor, cap and rotor, plugs, plug wires, cam, lifters, fuel pump, water pump, timing is right...all of this is new.

the Carb is fine, nothing wrong with it, and the car sounds great in idle, but will not stop backfiring through the carb. the Firering order and timing are checked and fine...

we have a Gremlin...and cannot find the problem...

have any suggestions?

ridge_runner
05-08-2004, 07:21 PM
are you sure the timing is right? what lift cam do you have? and whats the timing set at?

Nova 69
05-09-2004, 02:48 PM
I ran into the same problem with a freinds engine recently. He just had it rebuilt and it turned out that the new chrome timing chain cover he installed had the timimg mark in the wrong location. There are two different timing mark positions depending on what engine you have, they're about 20 degrees different from one and other. It sounds like a timing problem to me, I'd check to make sure you have the timing mark in the right location on the timing chain cover.

broughy84
05-09-2004, 10:34 PM
I too would definatley lean towards the timing. First thing i would do is get #1 to TDC and scratch time it again.

tupac
06-26-2004, 01:53 AM
make sure that your valves and cam are set right, being that your intake & exhaust valves are both closed, and your distrubutor is set to fire on #1,take off your valve cover on the drivers side spin it over ( but don't start) watch both valves on #1 when they both open & close the piston should be up firing, then check your distrubutor see if its on #1, if its not then you'll have to pull it out and restabe it.

smokeyburnouts396
12-06-2005, 07:03 PM
pull the dist. out and spin it 180 degrees and i bet your problem will be solved

nova68
12-06-2005, 11:10 PM
what kind of carb is it?

70Nova05
12-07-2005, 11:03 AM
If this just occured suddenly, check timing. Also watch your timing mark with a timing light. If it jumps around, your timing chain is lose, and perhaps jumped a tooth. Also check the distributer shaft for excessive play. Backfiring out of the carb is caused by firing with the intake valve open. This should be caused by incorrect timing or an intake valve stuck open. A quick compression test of each cylinder will answer the stuck intake valve question.

dnice386
12-08-2005, 09:45 PM
I had the same thing happen to me on my 76. Pull the distributor and turn it 180 degrees. You'll be all set.... good luck

ortamenx
01-10-2006, 11:21 AM
I had the same thing happen to me on my 76. Pull the distributor and turn it 180 degrees. You'll be all set.... good luck

You too? I got up one morning went out to my car started it up gave it gas and chug chug boom , backfire out the carb, only on slight depression of the gas, if I reved it I could get it to over "power" the dead spot and run, but if you let go and gave it gas again, chug chug boom. I instantly thought I have rounded a cam, or a vavle was sticking, thought oh no rebuild time. So I got on it again and held it floored, couldnt be a cam or valve or it would be backfiring like all hell floored with no where for the exhaust to go. I knew my plugs and wired were good, and in the right place drove fine before I put it in the garage before winter. So two probs down, nest was timing, puleed out number 1 plug and popped my cap off, rotor was in right place at top dead center. So timing was good. So carb, bad power valve? That could make it run lean, or an air leak, nope no air leaks, I have had probs with tranny ( I am rebuilding by the way) So I thought damn maybe the line to the vacuum mod was bad, lot of work for simple problem, nope, so fine can't be a valve not noisy enough, and works fine at idle and floored, Timing is good, Gas pressure good, no air leaks . . . so I rebuilt the carb, that's a fun three hours. Carb rebuilt, lets put it on, same thing not as bad, but same backfire. Buddy is telling me time to junk it bad cam, bad valve. . . . On night good and drunk I was messing with it turned my distributor abotu half way around and boom problem solved. From being online I've seen this probelm come up a million times, usually the same two things, carb/airleak you can blow a power valve easy espeically cheap one from cheap rebuild kits, or distributor needs yankes around a bit. Anyone else noticed this? Hope this massive post helps someone with similar prob, always start with simple things first, and if they don't work and you do have a possible stuck valve, 1 suggestion before rebuild. Run a butt load of flush through your oil and change it, good stuff, I usually put some diesel (no don't) or tranny fluid to help flush and clean the inside run it a bit, then drain, flush, and refill with good oil and like rislone or lucas, I had a car with a a sticking valve/badlifter, tick tick tick tick, come out of it and run for three years and I mean ran hard for three years until it started giving me any troubles.

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