Car backfiring and shooting flames after cam install
01-10-2010, 06:19 PM
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Car backfiring and shooting flames after cam install I recently installed a CC305 in my car after having the timing chain break on me. The car would start and run, but had a bad lack of power, I figured it was due to a faulty opti. The car would overheat, so I pulled the heads and fixed the problem, and installed a new opti. After doing all of this, now the car will not start without clear flooding it(gas pedal all the way down when cranking). It was throwing a code for the MAF, P0100, so I put my friends MAF on the car. It cranked up first try, but had a bad backfire out the exhaust. Anytime it starts, it backfires out the exhaust, but when you crank it and it wont start, it will backfire and shoot flames out the intake. I am 99% sure the opti is installed correctly, and that no wires have been crossed(I marked them before taking them off) and that the rockers are set right. I tightened the rockers to zero lash with the car running, and then 1 turn past zero lash. I am running stock rockers. Anybody have any ideas? Here are some vids, the first one is before
I fixed the overheating problem, the second is from today.
I fixed the overheating problem, the second is from today.
01-10-2010, 11:25 PM
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you mentioned your timing chain broke, was the engine over reved?
did you check for bent pushrods or valves when you had the heads off?
backfiring thru the intake usually means a lean condition
did you check for bent pushrods or valves when you had the heads off?
backfiring thru the intake usually means a lean condition
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01-11-2010, 10:06 PM
#9
Alright guys, I am helping with the troubleshooting of this car. We finally got it to run tonight, set all of the rockers to 4 threads above the rocker showing, and it fired right up, I then set all the rocker 3/4 turn past zero lash. The heads were pulled off after the timing chain broke, and had a couple of bent vales. My buddy took em and had new valves installed and had em re-worked. When he re-installed em the steam pipe was not put on correctly and caused the car to blow a head gasket. So the heads were pulled back off and resurfaced, then the motor was put back together. He has checked the plugs several times and can't find any that are crossed. However, now the car is backfiring out the exhaust. The car is on its 3rd opti since the cam install, but I am still leaning towards a wire being crossed somewhere, however I know for a fact all of them on the drivers side are right and I can see flames shooting out the ds header when it backfires, along with the passenger side. I installed the cam, and did it exactly how I did mine when I built the motor following shbox's write-up on his website. Heres a vid of the car, what do you guys think? The video is taken at night so you can't see much but you can hear it.
08-19-2010, 08:16 PM
#15
Not only this but are the wires good? Are any of your spark plug gaps off? You can try a spark plug tester that will let you visually see the spark.
Remember this quote, "If it doesn't fire in the cylinder it is going to fire in the exhaust." That popping noise is combustion occurring in the exhaust. Also if you have checked everything and nothing is working, pull your mufflers and make sure they aren't restricting anything.
edit: I have tried to put a timing light on my LT1 before and it didn't work, but on a SBC if you make a visible white mark on TDC on the harmonic balancer and then use a timing light while it is idling you can tell if there is a cylinder not firing or out of order. If the white mark you put on the balancer is bouncing around at idle then you have a missing cylinder somewhere. Unfortunately the method for troubleshooting this while the engine is running is to pull each spark plug wire one at a time while it is running to see if the problem stays the same or gets worse (I don't recommend this on a LT1 while it is running, shut it down before you pull the plug wires). If it stays the same you might have found your problem.
Another longshot is perhaps your valves aren't sealing properly or your springs pressure is shot. A leakdown test and a compression test will reveal if these are the problem.
Remember this quote, "If it doesn't fire in the cylinder it is going to fire in the exhaust." That popping noise is combustion occurring in the exhaust. Also if you have checked everything and nothing is working, pull your mufflers and make sure they aren't restricting anything.
edit: I have tried to put a timing light on my LT1 before and it didn't work, but on a SBC if you make a visible white mark on TDC on the harmonic balancer and then use a timing light while it is idling you can tell if there is a cylinder not firing or out of order. If the white mark you put on the balancer is bouncing around at idle then you have a missing cylinder somewhere. Unfortunately the method for troubleshooting this while the engine is running is to pull each spark plug wire one at a time while it is running to see if the problem stays the same or gets worse (I don't recommend this on a LT1 while it is running, shut it down before you pull the plug wires). If it stays the same you might have found your problem.
Another longshot is perhaps your valves aren't sealing properly or your springs pressure is shot. A leakdown test and a compression test will reveal if these are the problem.
Last edited by noice; 08-19-2010 at 08:23 PM. Reason: adding more info.
08-20-2010, 12:53 PM
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