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> > ------------------------------------ > > To send a message to this group, send an email to: > Chrysler300@xxxxxxxxxxxxxxx > > To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to > https://groups.yahoo.com/neo/groups/all/manage/edit > > For list server instructions, go to > http://www.chrysler300club.com/yahoolist/inst.htm > > For archives go to > http://www.forwardlook.net/300-archive/search.htm#querylang > ------------------------------------ > > Yahoo Groups Links > > > > > > ------------------------------------ > Posted by: "Ron Waters" <ronbo97@xxxxxxxxxxx> > ------------------------------------ > > To send a message to this group, send an email to: > Chrysler300@xxxxxxxxxxxxxxx > > To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or > go to https://groups.yahoo.com/neo/groups/all/manage/edit > > For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm > > For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang > ------------------------------------ > > Yahoo Groups Links > > > ------------------------------------ Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx> ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to https://groups.yahoo.com/neo/groups/all/manage/edit For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang ------------------------------------ Yahoo Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! 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