1929 Chrysler Series 65 cannot maintain 40 mph

Narve N · August 30, 2014

Anyone with experience on the subject or having observed something similar? My Chrysler Ser 65 will run all day below 40 and easily hit 50, but refuses to run properly for any length of time above 40 with the engine misfiring plus backfiring and gradually falling out. Changing down to 2nd the same will occur at 25 mph. I have changed spark plugs and ignition parts back and forth and believe a faulty spark cannot be the cause and neither can find any failing fuel supply. Carb is a Carter BB1 (overhauled), could it be that many of these came from GM Trucks and were not designed to maintain "higher" RPM? Is there a way to tell whether the carb is GM Truck and not Mopar (Plymouth)?

nzcarnerd · August 30, 2014

Have you replaced the condenser?

ply33 · August 30, 2014

A weak spark could cause the issue as the more pressure in the cylinder the stronger the spark has to be to ignite the mixture. Might be condenser as nzcarnerd suggests. Might be the coil (weak or connection opening up in it when it gets hot).

We had a '48 Plymouth on a cross country tour with us last year that I could have sworn was having fuel pump issues: Kicking and bucking, acting like it was running out of gas on long up grades and at higher speeds, etc. Turns out the issue was the coil: When power demands were high (throttle open more, so more charge in the cylinder so higher cylinder pressures) the spark just wasn't strong enough to ignite it properly.

hchris · August 31, 2014

Anyone with experience on the subject or having observed something similar? My Chrysler Ser 65 will run all day below 40 and easily hit 50, but refuses to run properly for any length of time above 40 with the engine misfiring plus backfiring and gradually falling out. Changing down to 2nd the same will occur at 25 mph. I have changed spark plugs and ignition parts back and forth and believe a faulty spark cannot be the cause and neither can find any failing fuel supply. Carb is a Carter BB1 (overhauled), could it be that many of these came from GM Trucks and were not designed to maintain "higher" RPM? Is there a way to tell whether the carb is GM Truck and not Mopar (Plymouth)?

Have you taken note of the color of the plug electrodes after a run ?

Ideally the electrode and insulated nose should have a brownish tinge if the fuel mixture is set right, a whitish color would indicate that its running too lean and sooty color too rich; either mixture fault will cause misfiring although being too lean will cause a backfire as well.

Start by analysing the plugs first before delving into ignition, timing, leaking valves etc. all of which could give you similar symptoms.

Narve N · August 31, 2014

Most relevant electric components have been changed around at least once, the coil and condenser are generic 6V items that might not fit this car especially well or might have quality issues. I will try to enrichen the mixture as I know I did turn it down a lot previously to get away from soothing. Stay tuned.

Narve N · August 31, 2014

Having fiddled with he carb for 2 hours I now am quite certain that the mixture etc adjustments does not affect the falling out at 3/4 to full throttle issue. I also tested a second condenser with no effect.

ply33 · August 31, 2014

Having fiddled with he carb for 2 hours I now am quite certain that the mixture etc adjustments does not affect the falling out at 3/4 to full throttle issue. I also tested a second condenser with no effect.

Is that updraft B&B like the later down draft versions where the mixture adjustment only affects the idle mixture? If so then I would not expect it to make any difference.

I think checking the plug color after running it in the conditions that cause the problem is next. Might help determine if it is the carburetor or the ignition.

keiser31 · August 31, 2014

Narve. I had the very same problem with the carburetor on my 1931 DB when I had the Carter BB1 on there. Plus the fact that the BB1 leaked fuel out the bottom like a sieve. I got rid of it and found the correct DRT-08 and it runs like a dream, now.

hchris · September 1, 2014

Having fiddled with he carb for 2 hours I now am quite certain that the mixture etc adjustments does not affect the falling out at 3/4 to full throttle issue. I also tested a second condenser with no effect.

As ply33 said, the mixture screw is only affecting idle mixture, as your problem is occurring at higher revs there will be a different fuel circuit at play within the carb; just pull the plugs and have a look at their color.

Sasha39 · September 1, 2014

Hi Narve,

Well if you’re running around at 40 MPH it sounds like you fixed the leaking Master cylinder problem you had and that’s a good thing, with your carburetor problem I see that you have stated that it had been overhauled could it be that the float level was not set correctly??, send me a PM with your e-mail address and I’ll send you a copy of the Service procedure for the carburetor is about 13MB in size so can’t attach it here, did you do the overhaul or was it done by someone else as they might have failed to put the high speed circuit spring back in, anyway you’ll see it all in the service procedure when you get it.

Anyone out there that wants a copy of the Service Procedure just PM me and I'll send you a PDF copy very handy for all models of the Carter BB up draft carburetrors.

Narve N · September 5, 2014

Thanks a lot for all the tips and especially to Ply33 for mentioning the coil as a possible culprit for investigation. Turned out my mechanic last year had identified the 85 year old original coil as past its usable life with falling out as it got hot, and he installed a fresh unmarked 6V alongside the senior to provide better sparks. He however kept the old coil wired in parallel in the primary circuit and this must have drained the primary voltage too much - or something like that. Anyhow, as a replacer and not a repairer I today installed a 30-year old Bosch 6V coil that had tested OK and this time kept the 85-year old original fully out of the circuit. The result was astonishing with no more annoying hiccups and misfiring, the car went straight to 50 mph before I had to ease off (60 kph zone with traffic). I also have my own Test Hill (Brooklands Race Track inspiration) where the car improved on my previous best of 30 mph with a new record of 34 mph. Having changed everything else at least twice and adjusted the carb about 10 times, I must say it pays to be persistent and especially to ask the AACA Forum!

keiser31 · September 5, 2014

Narve, that is such a stunning roadster!!

Sasha39 · September 5, 2014

YES! Beautiful car, have just sent the Service Procedure manual to your e-mail address, hope it of use to you.

Edited November 5, 2018 by Sasha39 (see edit history)

Rusty_OToole · September 7, 2014

In those days Chrysler named their cars for their top speed, the Chrysler 65 model was supposed to be good for 65MPH but in good tune, would do a little better, especially the roadster.

If your car is in tip top condition it should do 65 to 70 MPH or 110Km per hour. Out of respect for the car's age I would not try it, but it sounds as though your car could do it.

ply33 · September 7, 2014

In those days Chrysler named their cars for their top speed, the Chrysler 65 model was supposed to be good for 65MPH but in good tune, would do a little better, especially the roadster.
If your car is in tip top condition it should do 65 to 70 MPH or 110Km per hour. Out of respect for the car's age I would not try it, but it sounds as though your car could do it.

Top or cruising speed?

I've read it both ways at different times and in different books. Never saw anything about the advertised names, which I think were different than the engineering model codes, in period literature that explained that.

For what its worth, a number of years ago I followed a fellow in a stock '31 Plymouth four door sedan, not too distantly related to the 4 cylinder '28 Chrysler model 52, to a meet that was about 250 miles away. He set the pace and did pretty close to 50 MPH the whole way.

nzcarnerd · September 7, 2014

Our 1929 Plymouth, with 80,000 miles on the clock, will cruise happily at just under 50 mph. These are taller geared at 4.3:1 than the smaller Chrysler sixes and sound less stressed. I know of modified ones which will cruise much faster.

Narve N · September 7, 2014

The subject is interesting as there are as many views as there as viewers. According to the 33 Parts manual, a Series 65 could be had with 4.3, 4.6 or 4.9 gears and others models range all the way between 3.58 and 5.2. My understanding has always been that the lighter cars (like a Roadster) has the tallest gears meaning that they were the (only) ones that could reach and maintain (equals cruising?) the Series claimed number as speed - like 65. A Roadster would then be the fastest car of a series.

However, when Chrysler brought the slightly newer CG to Daytona the reached and maintained top speed differed only a fraction between the Sedan and the Roadster, keeping in mind that the CG Roadster cannot lower its windshield for lesser wind resistance:

Anyone seen similar test results for any other vintage Mopars?

Rusty_OToole · September 9, 2014

So far as I know it was top speed. But, a good one would exceed the "rated" speed and might well cruise at the advertized speed as long as the roads allowed.

Rusty_OToole · September 9, 2014

According to Tom McCahill the Daytona Beach sand had quite a bit of drag, and imposed a 10% "tax" on top speed. In other words if a car would do 91 on the sand, it should do 100 on a hard top road.

Rusty_OToole · September 9, 2014

Lots of car makers in the twenties and thirties went record setting. One that is often forgotten is the sensational performance of Pierce Arrow.

To publicize the new twelve, Pierce-Arrow arranged for the race driver, Ab Jenkins, to drive a Pierce-Arrow on the Bonneville Salt Flats. An unofficial, 24-hour run was done in 1932, with an average speed of 112.91 miles per hour. In 1933, Pierce-Arrow repeated the run, this time with AAA observing and conducting the run. This time, Jenkins drove 3000 miles in 25 1/2 hours, averaging 117 mph. This trial broke 66 official AAA speed records. In 1934, another run set a new worlds speed record of 127 mph for 24 hours.

The first year this was a stock roadster with the fenders, windshield etc removed. In 1933 and 34 they used the stock chassis with an open wheel racing type body, but on the very bulky Pierce chassis and with a mildly modified Pierce Arrow V12 engine.

Notice the performance, 112 mph the first year, 117 the second, 127 the third, average for 24 hours continuous running.

This was incredible performance for any car, but the Pierce was not thought of as a fast car, it was a limousine type car for tycoons and dowagers.

To put this in perspective, at this time Rolls Royce warned their customers not to drive for more than 5 minutes at full throttle for fear the engine would blow up. And a few years later the makers of the Grosser Mercedes supercharged straight eight, warned against driving for more than 2 minutes with the supercharger engaged for the same reason.

The Rolls Royce had a top speed under 90, the Mercedes would just top 100 with the supercharger engaged. Neither could have averaged 100 for even one hour, unless towed by a Pierce Arrow.

Edited September 9, 2014 by Rusty_OToole (see edit history)

Rusty_OToole · September 9, 2014

The Pierce Arrow record was broken by a specially made, Duesenberg with straight eight, double overhead cam, supercharged 7 liter engine called the Mormon Meteor.

The next year the same car set a new record, but this time it was equipped with a Curtis Conqueror aircraft engine.

Interesting that it took the legendary performace car Duesenberg, with supercharger, to beat the unsupercharged Pierce. Even more interesting that the Duesenberg was stretched to its limit to do so, otherwise they would not have needed an airplane engine to top it.

1929 Chrysler Series 65 cannot maintain 40 mph

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