djg944

Hi all,
I have recently developed a missfire on my gt. Problem occured while getting on the car @ a high speed/rpm. I switched coil, plug, and injector still have the problem, missfire and very gas soaked plug. I think I have exhausted about all variables outside of the motor, what is the possible extent of the internal damage I may have caused? Also the car did not come factory with s/c, is there a possibility the motor can't handel extra boost? What test should I run know? Any idea if I can convert from sohc to dohc, (cobra heads)?

2001 roushe edition gt
4.6 vortec supercharger 6lbs boost 38lb injectors
39,000 miles

FEAnt

The stock internals should be for 400-450hp. 6 lbs of boost is not a tremendous amount, but...Did you ever have the vehicle tuned to ensure that the air/fuel ratio was correct? Perhaps a lean condition resulted.

There are resources that can you can find online that can cover the 2v to 4v conversion. More importantly is that if you are looking for big power you will need forged internals. MM&FF magazine has some articles on building 500hp on 2V head engines. There is potential there.

djg944

Good advice, I will look into fuel/air ratio. I am definetly very lean, I have vaporized spark plugs on a few occasions. I guess my main question is if my plug and coil pac is doing its job (great spark), why is the plug still fuel saturated??? I will do the compression check on the cylinder and let you know the results.

Thanks for the reply,
DJG944

hibachi1

As mentioned before, get the thing tuned on a dyno. Have them plug in the O2 sensors and check AFR. The odds are that if you are smoking the electrodes off your spark plugs, some internal damage may already have occurred. As far as the one that is always fuel soaked, it sounds like that one may have a coil pack problem and that one is not firing. Raw fuel is getting into your exhaust which is causing the misfire. Stay out of boost for a while. When extra fuel gets into the cylinders, it will wash down the cylinder walls, and destroy the oil control ring. No compression.

Ron

FEAnt

I am betting the A/F is way screwed up. Too rich under cruising, but too lean at WOT. Like hibachi said, stay out of the boost until you get it to a dyno for a real tune.