Re: {Chrysler 300} I hope I did not buy an engine with a problem...

seconding all this , a lot of overthinking going on , — you always want best lean idle not something else for any reason . The only way to get that is a vacuum gauge , as it coincides with highest vacuum . Get one with large face , be sure base timing is right on Disconnect advance so it is not fooling you .

Heat range is impactful at high speed running not so much at idling . Idling has so few explosions per second it is negligible heat and , the engine being unloaded , the burning is light and produces almost no heat compared to full load at 5000 rpm . Heat range is about detonation — use factory recommended , modern iridium or rhodium plugs . They are just better in the long run and tend to have a wider heat range .

It is true that too cold a plug will impact idling in the sense that if fouled due to missdjusted rich mixture or slight oil bypass they won’t burn themselves clean as easily with normal driving . Going hotter risks detonation on high compression engines . Hole in piston ! Use factory ranges unless racing or towing.

As mentioned a while back it needs high speed running and mobil one for a thousand miles to clean er out . These

are 150 k -200k motors sitting still is the problem . After that 1000 + miles if still bothered do a compression test . It will be fine . Doing it after sitting can be highly misleading info .

John g

Sent from my iPhone

On Feb 22, 2023, at 5:15 PM, dplotkin@xxxxxxxxxxxxxxxxxxx wrote:

I agree with Ron that a vacuum gauge would be helpful here. It may tend to the side of far fetched to expect a 60 year old engine of unknown mechanical condition to idle glass smooth on pump gas. Time to give this engine a full physical, vacuum gauge, fuel pump pressure, timing light, detailed distributor/vacuum advance inspection and compression test. Its always better to determine problem via diagnostics than swapping parts.

-----Original Message-----
From: "'James Douglas' via Chrysler 300 Club International" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Sent: Wednesday, February 22, 2023 12:05pm
To: "Chrysler 300 List Server (chrysler-300-club-international@xxxxxxxxxxxxxxxx)" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: {Chrysler 300} I hope I did not buy an engine with a problem...

I pulled the NGK plugs with a #7 heat range. They have about 200 miles on them. The number 1 plug, I had it out and I cleaned it, before I drove back to SF it was worse than the clean plugs but not as bad as the darkest ones in the photos.

As the photos show, some plugs show fouling. The engine is not producing smoke on acceleration or deceleration.

I put in new plugs with a #5 heat range (hotter) and will see what I get. The idle feels a little better, but not dead smooth.

Issues on both sides if you look at the photos.

Next up is looking for vacuum leaks.

James

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