| Hi, You really should go back to stock ,— it is not just jet size , it is the profile of the tapered mixture control rod responsive to vacuum across the rpm range and the operation of the vacuum advance curve just off idle which were all carefully designed. And all that are ruined , compared to factory calibrations by say operating the two carbs at once . Or low vacuum due to a hot cam Add in that lower vacuum if cam has been significantly stepped up and that leads to lots of problems . I think the 300 had 280 advertised duration on the hemi , pretty hot for a street motor. You go more , idle has to go up some. you get stalling then when pushing drive . And no power at 1000 rpm Today they would add a loose converter can’t do that with the old torque flite. They worked very hard to get a balance between performance and drivability , they did very well . It is not a race car now, 375 hp you can use is a lot better than 400 that barely runs unless you are at 135 mph . ( if you ever get 400, often you lose hp)
In an absolute 2022 sense they are not fast cars anymore , rather classics that we can drive , —-souping up a well balanced ,well thought out 392 as one might safely do to a stick Chevy 283 brings nothing but grief . But almost all of us do this once .. (smile ) I did it to a J , cam and trans shift kit , It shifted at 6000 + or so blew off all the belts , wrecked a few radiators caused me to walk a bit . Stalling on engaging , hassles with power brakes. Older now , would think twice .
On this —- first step is go to totally stock carb operation, if that does not solve it , you may need to go to 280 or less cam . What cam duration is in it now? “ great mechanics “ do not know more than the guys who designed it ,ran it , set records with it when new , that is just a fact , sort of ? Right ? They sorted it all out , probably 30 of them .. engineers. Pump shot if poor might help , but that has to be way off to really hurt , — but be sure it is working . I have encountered in last few years where check balls or brass check valves in that part of carb get crud on them from (?) ethanol , kind of a white deposit , when sitting a year or so . No pump squirt= can’t start car but will run once started . FYI . .. John G Sent from my iPhone On May 7, 2022, at 4:27 PM, Ray Melton <rfmelton@xxxxxxx> wrote:
True - But in this case, how does the mechanic know what size to
drill? And which jet(s)? And in rear carb only or both? Are
replacement jets available if the bigger jet produces no change or
makes things worse? Drilling is largely irreversible.
Good instrumentation on a series of chassis dyno runs could
really help pinpoint the problem and lead to optimum performance.
(Lotsa labor changing jets - assuming you have alternatives
readily available - and making adjustments in between runs =
pretty costly, but even at $100/hr could be worthwhile investment.
) Unfortunately, I don't have access to such facilities anywhere
near my small town in New Mexico.
A good place to start with the carburetors is with Chrysler
Service Bulletin #1002-CH, Dated March 1, 1957. (Available
through Club website - Technical) And of course, the Factory
Service Manual.
Personally, I would go back to the original stock progressive
configuration, ensure baseline adjustments per the Bulletins and
Service Manual, then perform the recommended carb modifications
and go from there.
Ray Melton
************************************************************
On 5/7/2022 1:58 PM, Gary wrote:
Gary G.
With a No. and letter drill set you can
dill jet to any size you need.
Gary
Sent: Saturday, May 07, 2022 12:25 PM
Subject: Re: {Chrysler 300} Need more fuel!
Ray,
Thank you for your way over my pay grade response.
Mechanic is very talented and has some very high $$$$
builds to his credit.
That said, his main business is high end Resto Mods.
Did a buddies '41 Cad coupe on Art Morrison frame
with 2021 Cadillac Hot Engine and 8/10 ? speed tranny.
Very High end builds, yet he will work on old Detroit
iron like our beloved 300's.
I like your suggestion re the service bulletin update
and will start there and let you know how it goes.
Best Regards
gary gettleman
The once "Golden State" (but not so much any
more) of California.
Hello Gary -
Sounds like it could be insufficient accelerator
pump shot. Which jets is he suggesting to be
changed, and to what size? How did your mechanic
decide which jets to change and the new size -
anything scientific or just WAG? How will you find
those jets for such an obsolete carburetor? Even if
jets for the later Carter AFB would fit, is the
internal fuel/air flow circuitry the same as for the
WCFB? Since the 300C was originally intended to run
on only one carburetor at low RPM, you may have
upset the A/F ratio right off idle when you
converted to synchronous (non-progressive)
carburetor function - going too lean because of the
unintended extra airflow from the other carburetor.
Have you incorporated the carburetor modifications
recommended by Chrysler in Technical Bulletin #364
of July 16, 1957? That may/may not help, but it
couldn't hurt. I had Jim McGowan do that mod when
he restored my carburetors - excellent workmanship
and results!
Depending on the elevation where you primarily
operate, you might also want to consider different
metering rods, too, although that will not affect
your off-idle stumbling issue.
Ray Melton 300C in New Mexico
**********************************************************************
On 5/7/2022 12:31 PM, Gary Gettleman wrote:
To All the Great Folks in 300 Land.
Apparently the cam that we installed during
the C engine rebuild is a bit lumpy as compared
to the stock cam.
Have what I would call a momentary stutter
when the right foot presses down.
We adjusted carb linkage so instead of
running on 2 barrels it's now on 4, which has
improved performance, but still get the
occasional hiccup.
Mechanic said we need to swap out the jets
for larger size and that will solve problem.
Figure someone else has had this problem and
would appreciate your help with this issue.
Thanks to all.
gary gettleman
300 C Export
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