First, I will mention that I never received Michael's original msg through the listserver; I only received Henry's response. I have noticed that I'm not receiving all the l.s. posts seems to be hit or miss and could be my ISP.
Anyway, as Henry mentioned, this could be a weak fuel pump and/or clogged filter or related fuel flow issue - at speed (higher load). Consider replacing the fuel pump and fuel filter. But first, consider all ignition issues.
The distruibutor may need a complete overhaul. The Pertronix installation is not causing the problem - it is either "on or off." A weak coil and/or weak spark could cause this as well.
The spark plug wires on a J are a weak link. They need to be in good shape and heat sleeved at the spark plug boots and if crossing over the headers (wire routing may not be correct).
Assuming the damper hasn't shifted (big assumption!) and the timing marks are correct, I would not set initial timing at 15 degrees BTDC. That was an early spec and it was changed via a tech service bulletin to -12.5. As I vaguely recall, Al's J did not have the original J engine, may not have solid J heads, may not have correct cam profile, who knows? That's ok, but you have to tune to what's in the car not necessarily the original spec.
Yes, you can substitute a new electronic distributor with vacuum advance (but no tach drive). You might also find a new electronic distributor that will work with tach drive, but it will not have vacuum advance, and may even have a fixed or limited mechanical advance as it will likley be set up for racing.
Let's face it, the tach is largely for show. You have to take your eyes off the road to read it (a major complaint when these cars were new) and unless you have a trans/linkage setup problem you don't really need it.
FYI. my J was modified under previous ownership to hydraulic from solid cam/heads but retains the original J engine. I believe it's a Mopar purple shaft in the engine. Because my tach drive distributor at present is kaput, I installed a new electronic distributor with vacuum advance (no tach drive) several years ago and I installed the lightest springs for very quick mechanical advance (which is correct for a J). Timing set at -10 with total advance to -34 degrees all in by 2500 rpm (vacuum adv disconnected). In other words, I tuned to the engine setup in the car, not the J spec. Throttle response is instantaneous, no detonation, and the car is very quick.
Keep at it, Michael, you'll get there!
Carl B.
------ Original Message ------
Date 7/2/2024 10:55:43 AM
Subject RE: {Chrysler 300} Re: Chrysler 300J lack of power problem
Measure the maximum advance (no vacuum) to ensure it doesn’t go above about 35 degrees as a first check. You may have more advance than you think due to wear. If ok you may well have a fuel flow problem at speed. Idle pressure is not a good indicator.
Henry
I would appreciate suggestions from the more experienced members of the club with long Ram engines and tac drive distributors. We purchased this J from Al Vannic and are trying to get it to run correctly. I am experienced with Mopar RB engines.
The vacuum advance plate in my distributor was rusted and corroded, would not move, could not be fixed. I elected to replace the points with an electronic system with a vacuum advance and installed a Pertronix Ignition. Set it at 15 degrees advance as per the manual. The vacuum advance is working.
The car started easier but problems continue. When driving at 50-60mph it pulsates quite rapidly and will if I try to accelerate it just bogs and has no power. It acts as if it is starving for gas. I checked the fuel pump pressure and it is 5.5 psi at cranking speed. Meets spec.
It was suggested to me that the problem could be a worn advance mechanism in the distributor. Has anyone experienced this condition? One suggestion that I saw on u tube was to replace the distributor with a newer electronic unit and eliminate the tac drive. I can do that but want you to keep original.
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