Re: [Chrysler300] Carter AFB - Edlebrock carb help needed

On Sep 1, 2014, at 12:54 PM, Michael Moore mmoore8425@xxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Rick,

Thank you for your informative note. I have religiously followed the workshop manual to adjust my carbs (300H). Many years ago (I've owned it since 1966) I had no problem tuning it up. In recent years, it sat idle for a number of years and I finally had the time to get it back on the road. I was not happy with how it ran, even less so with how it stopped.

I fixed the stopping problem then worked on the running problems.

A friend who is most impressed with his mechanical skills spent some time helping me. That got a bunch of linkages bent up. I later replaced the distributor which helped immensely and had a top shop rebuilt the carbs with all new linkages. Suspecting the damper and timing mark, I had it rebuilt. I also adjusted the valves hot,and running, measured them, and for reference later checked them cold and found ca .002 difference between hot and cold.

Dwell is correct, timing is correct-but I still do not like the way it runs. I have followed the work shop procedure several times, always dissatisfied with the results, My professional mechanic (not the genious who bent up the linkages) , who owns a Corvette, also with dual AFBs says its just because of the gasoline.

One thing I am unsure of is tuning the 4 idle screws and looking for rpm increase or decrease, I can sometimes turn a considerable amount and not see it go up or not. How do you use a vacuum gauge for that?

Because we have owned the car so long, and do enjoy it, I have been wondering about installing a single 4-barrel carb on another manifold for normal driving-but then what?

Why would I ever install the 2x4 manifold again?

1. What would you do.

2. What do you use the vacuum gauge to adjust the carbs. (I am using a tach only)

Thanks,

Mike Moore

300H

On Sep 1, 2014, at 12:28 PM, 'Rick Vitek' rpvitek@xxxxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

With respect to Q1, are you sure if it’s too much fuel or not enough? Mark’s post is more likely, namely it’s a vacuum management issue. Lower engine rpm’s and thus less vacuum combined with braking (and thus with power brakes actuating and affecting vacuum).

Q2: Putting a new Holley carb on it may fix it, as might putting on a new Edelbrock. There is nothing intrinsically better about the Holley design ( though a lot of aficionados for either would love to argue this point). In either case you’d be putting on a new carb where everything is adjusted to the proper spec’s and working right. After all, the AFB has served well on a lot of Mopars through the years.

The following is not directed at you or anyone in particular but rather hopefully provides a background for looking at any carb problem. A look at the history of carb development shows system after system added on to correct limitations of the basic design. For example in response to a problem of stalling during hard cornering Holley added the “cathedral” bowls to prevent fuel starvation. So what was a simple mechanical system in the twenties morphed into a complex system by the seventies, probably the most complex part of the engine accessible to the operator. By that I mean your average owner wouldn’t tell himherself “I think there’s a problem with the tranny so I’ll drop the pan and start fiddling around” or “ the steering is not right so let me open the gear box and see if anything pops out”. Your average operator with an engine problem is however willing to pull the air filter, stare at the carb, and saying something like “ I don’t think the choke is pulling off soon enough so if I just bend that linkage arm the choke will be more open and the problem solved”. Since its an integrated system that bending of linkage may open the choke but also affect something else in the carb. Thus a lot of carbs out there may have been tweaked since their latest rebuild in ways they were not intended to be tweaked but which the operator/mechanic thought was a good idea at the time. Worse yet, some have been “rebuilt” without checking to see if the linkage has the proper dimensions/operation. Add to this a thousand gallons of gasoline (with its contaminants) that are pumped through that carb (and its close tolerance parts) per year. Sometimes it’s as simple as a particle blocking a port. The problem however often involves degradation of multiple systems within the carb. As such it often involves going back to first principles or epistemological analysis to diagnose, namely how do we know what’s working right. Last year I started working on a ram engine car that was hard to start, often stalled, and gave underwhelming performance when running. The car was advertised as having recent professionally rebuilt carbs – and I think they were. By the time I went through using the factory specified procedure for setting up the throttle linkage from the accelerator pedal through the final connection to the carbs, setting the entire carb linkage through the procedures given by Carter, new tune up parts and adjustments, adjusting both carb’s mixture and idle, replacing all vacuum tubing, and making sure the tubing was connected to the right ports I had an engine running just great. After each procedure the car ran a little better but no one procedure “fixed” the problem. When I see someone ask “how many turns out is this mixture screw supposed to be?” I think back to the service manual. If there was a hard number it would be in there. Rather you can start at a certain point but then have to adjust to the particular engine you’re working on due to e.g. manufacturing tolerances and wear. A lot of guys may be able to use their ears to tell how an adjustment affects rpm’s but I have to use both tachometer and vacuum gauge to see the effect. This is especially true on multiple carb set ups where you have to go back and forth several times to get them balanced.

I realize this doesn’t solve your problem. Perhaps, based on your particular setup you could start by putting a vacuum gauge on the carb and see the response when going through various scenarios such as 2000 rpm to fully closed throttle, brake actuation etc.

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Mark Lindahl mplindahl@xxxxxxxxxxxxx [Chrysler300]
Sent: Monday, September 01, 2014 12:25 PM
To: christopher; Chrysler300@xxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] Carter AFB - Edlebrock carb help needed

Christopher,

I am having the same problem with a Carter AFB 3256SA in my '63 Chrysler 300 conv. Sudden stops can cause the engine to stall. Also, a quick slowdown with a right turn causes engine to nearly stall. I increased idle and this helped a bit, but I don't think this is the complete solution.

I find that when I downshift before making a quick right turn, there is less of a stalling problem. When I have the trans in neutral, the problem is worse. This leads me to believe that as long as the wheels are turning the engine (in a downshift condition), the proper amount of fuel is getting to the engine (under load).

My 1st guess is that some of the small carburetor ports may be semi-clogged and the proper amount of fuel gets sucked in the engine only under high vacuum (load conditions)?

Let me know your thoughts.

300ly,

Mark Lindahl

On Monday, September 1, 2014 6:35 AM, "christopher thelastbestgenius@xxxxxxxxxxx [Chrysler300]" <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Q1. Motor with a 60s/300 style 4bbl Carter AFB type carburetor on it - brake real hard, near panic stop, and motor stalls as if gas/fuel flooding/pouring out of carb float chambers and into the carb/motor guts/intake, and it richens motor too much so it stalls - is this common with thyis type carb in this situation, AND IF SO IS THERE A CURE??
The same carb is now sold as an Edlebrock
Q2. - tuner guys have said put a 4bbl Holley on motor to cure it instantly - DOES THSAT SOUND TRUE?

Christopher in Australia - 1st day of spring, and/but just rained hail and sleet outside. And for US300ly grain farmers, many Southern Australian winter grain farmers badly need rain, plus savage frosts a while back totally ruined many crops before they even ripen

I see there was a seemingly nice red 300C on ebay last week, at around $57k, no takers. I realise 300G looks is a maybe acquired taste, so that one selling in the $60ks was not too surprising given the sad situation re both its's owners, despite it normally should have bought maybe a 25% higher price than usual due to it's known quality/standard?.\
And in the past, was $60s to 70ks a fair/good/average figure for real good '57-61 300 Coupes, so maybe not much changed. But against that one of the bigger Market Report email/websites, just posted few days ago, that now annual Monterey Sales just ended, averaging all big US auction Sales/Results, prices up around 30% - not seemingly with 300s though.
Anyhow, key thing is enjoy driving them, as what they worth only any good if you selling!!

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