RE: [Chrysler300] 300G Missfire

["'Ron Waters' ronbo97@xxxxxxxxxxx [Chrysler300]" <Chrysler300-noreply@xxxxxxxxxxxxxxx>]

Nobody's commented on this as yet, and it may be only tangentially related,
but I would be concerned about the quality of the rebuild. If the engine
only has 30,000 miles since the rebuild and your compression reading is
115-120psi, then this is not good. By contrast, one of my classic cars has
over 200K on the original, never-rebuilt engine, with compression readings
in the 125psi range. My concern is that the potentially low-quality rebuild
issues are only surfacing now. 

Please let us know the condition of the #3 and 5 spark plugs when you remove
them.

Ron

-----Original Message-----
From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of Richard Osborne reomotorsports1@xxxxxx [Chrysler300]
Sent: Monday, March 30, 2020 3:19 PM
To: 300 Club Group
Subject: [Chrysler300] 300G Missfire

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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Posted by: Richard Osborne <reomotorsports1@xxxxxx>
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Posted by: "Ron Waters" <ronbo97@xxxxxxxxxxx>
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