Ron — That may be due to adding more cam timing at idle ,crank speed — what is important is all cylinders are about the same , as all 8 cannot all be poorly rebuilt?One lower is the usual indication of a rebuild problem . 120 even is ok — I think — as also depends on battery condition , starter , oil grade thickness, temp etc ,?? Are all
Plugs out , throttle open etc .4 % is nothing?
You can usually even hear a bad cylinder as uneven cranking noise ?
Sent from my iPhone not by choice
> On 30 Mar 2020, at 6:34 pm, 'Ron Waters' ronbo97@xxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:
>
> 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
>
>
>
> ------------------------------------
> Posted by: Richard Osborne <reomotorsports1@xxxxxx>
> ------------------------------------
>
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> ------------------------------------
> Posted by: "Ron Waters" <ronbo97@xxxxxxxxxxx>
> ------------------------------------
>
> To send a message to this group, send an email to:
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