Hello,
My G engine is mostly stock. I have a Pertronix ignition and a Mopar Performance Cam (Which I degreed to the ORIGINAL Ram engine specs, not the Mopar Perf specs) and lifters. Stock pushrods and rocker arms. The block was over-bored .040 therefore it had new pistons installed. This engine was built close to 20 years ago and I am guessing I have put around 20-30,000 miles on it since. Otherwise, engine is stock.
Last Fall, my son and I drove the car approx 120 miles to a car show. On the way home, it developed a miss, a cylinder or cylinders not firing. It seemed to get worse as we continued home and the freeway.
The car was parked and only taken out of the garage once or twice for very short drives since then. The miss seemed to be still there, but not as bad as it was on the freeway. A few weeks ago, we got it out to take my son to his Confirmation. On the way to church, the miss turn into a serious miss-fire. It was violent. It rattled EVERYTHING. clearly not a miss, but cylinders not firing when they should. I did not notice any backfiring thru exhaust or intakes.
When replacing the spark plugs. we found #3 and #5 electrodes squashed and therefore zero gap. There was no evidence of mechanical interference (broken valve,piston…). Also, I have always run the car hard enough that it is difficult for me to believe there is any carbon buildup which could’ve broken free and caused the spark plugs being compressed. We ran a compression check and found each of the cylinders very close and good (115-120). We also replaced the cap and rotor. Plug wires were not replaced as I don’t have an extra set and the wires on the car appear OK.
The car fired OK and seemed to run good, there was a very slight hint of a miss, but otherwise seemed OK. I let it idle and get up to temp. On the test drive, it started to miss-fire again, and again it was violent, massive vibrations throughout the car. We brought the car home and parked it. I noticed the front face of the intake manifold on the drives side (in front of the master cylinder) looks to have exhaust gas residue on it. I have yet to re-fire the car and feel for exhaust leaks, nor have we removed the spark plugs, but I am suspecting there will be issues with #3 and #5 agains as they are positioned close to the intake manifold where the exhaust gas residue appears. While the car is at idle, no exhaust leak can be heard.
I'm asking for suggestions in trying to diagnose what may be happening, prior to taking the intake and valve cover off? I’m more inclined to believe this is a mechanical problem vs an ignition issue. Could this be wiped lobe(s) on the cam? Could a lifter collapsed? Bent pushrod(s)? What else?
Thank you,
Richard Osborne
Columbus, OH
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