Choke issues... with Cool Carb plate installed. Carter AFB 4200

James Romano

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Anyone have anything positive so say about these things? It looks like my choke is all screwed up from this thing. The previous owner of my car had a Cool Carb heat shield installed on the car as he stated he had issues with the fuel getting vapor lock. I've heard both good and bad about these things, personally, but I don't think its worth having. It gets hot here in Long Island, but not for long. Also, I've been running 93 and adding TC-W3 into my fuel, so I don't see vapor lock being an issue anymore. I've also sorted a lot of issues to the fuel system that I found were all wrong, so fingers crossed, I won't see vapor lock in my future.

With the plate installed, the carb (Carter AFB 4200) sits about 5/8" above stock height. On the carb, the choke operating link was bent to **** because it looks like whomever installed this plate tried to compensate for the new carb height by working that link, instead of the divorced choke mixture adjustment.

My issue at this point is that she starts great... warms up no issue. Kick off the choke, good for a few minutes and then she start loping like I have a huge cam in it, then dies. After sitting a while, very hard to start. Smells like it's loading up. Finally when started... I'll be driving it around for a while, pull up to a light and sometimes the loping starts again. Sometimes no issues at all. Sometimes I'm running at fast idle. Car runs great on straight throttle... but hit it for kick-down or fast acceleration... nothing. I've opened the hood to check the carb while it was loping and I could see the choke diaphragm pulled in and the choke on. I've adjusted the mixtures per the FSM, no help. I've had it where the choke reset itself as I pulled up to a light and I'm sitting at fast idle trying to kick the thing off.

The reason for the rebuild is that I can see the top plate gasket is leaking like a sieve even after I've retightened the screws. I figure a good cleanout and a re-gasketing won't hurt anything but my pocket. I took off the carb off and will be sending it to Dana for a rebuild. In the meantime, I really don't want the Cool Carb plate on the manifold anymore. I'm going to ask him to replace the bent choke link, or bend it back to normal stock position.

I'm looking at making this all OEM and getting it back to square one as this plate seems to be causing more aggravation than it's worth having installed. I'm pretty sure the height and the screwed up adjustments are causing the problem with the choke. Does that sound about right?

Thanks.

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That choke pull off linkage is definitely butchered. First of all is your heat riser working or do you have headers. I am thinking that the choke pull off is set this way to open your choke more to compensate for a heat riser that’s not working properly. The pull off is really only there to open the choke on start up and then as it the engine warms the heat riser heats the choke and it begins to open.
 
I never found the carb cooling plate to be of much help although I tried the sandwich style that was popular back in the 1970's. As noted, the pull off linkage is beat up. Having the pull off linkage too short will cause the carb to run lean on a cold engine, not rich, so I suspect you have a needle and seat problem or a bad float in your carb.

Dave
 
My riser is toast. It was already broken and since I had my manifolds ceramic coated, I safety wired it permanently open. I know that's kind of an issue, but once the car is warmed up, I shouldn't be fighting the choke anymore. It should switch over to the divorced choke thermostat.

TW-C3 ... sorry...had it transposed. It's marine 2-stoke oil.
 
My riser is toast. It was already broken and since I had my manifolds ceramic coated, I safety wired it permanently open. I know that's kind of an issue, but once the car is warmed up, I shouldn't be fighting the choke anymore. It should switch over to the divorced choke thermostat.

TW-C3 ... sorry...had it transposed. It's marine 2-stoke oil.

A disabled heat riser would cause the engine to be rich at idle because the engine will warm up slower and the choke will stay on longer than it should.

Dave
 
There was no fixing the riser. The problems also occur after I've been running at temp as well. The choke just seems erratic at best.
 
There was no fixing the riser. The problems also occur after I've been running at temp as well. The choke just seems erratic at best.

In a perfect world you could run a modern carb with an electric choke, but then you would not be in original condition.

Dave
 
I looked at the Cool Carb plate at Carlisle one year. It looked OK, and I was asking about it and the guy selling them turned on the BS. He started telling me that I needed to buy his "special" carb hold downs. They looked alright, but the price was a touch high for some stainless steel set screws, nuts and washers. He then told me that stainless steel doesn't conduct heat! I asked him to repeat it, just in case he misspoke... and he said it again.

I tossed the piece I had in my hand back on the table and said "Yea, OK" and walked away. He got a little irritated about it, but I won't buy anything from someone that figures I'm stupid.
 
To me, adding oil to the gas sounds like it might make problems for the carb. I'd be interested to hear other opinions on that.

A lot of folks used to run some 2 cycle engine oil to slow down the wear on the valve guides and seats. 2 cycle oils are heavier than gasoline and tend to settle out of the gasoline if the vehicle is left sitting, say over winter. That is why you always run a chainsaw or other 2 cycle engine out of fuel before storage, otherwise the dang thing wont start next time you go to use it. I think it was HOT Rod magazine that suggested the two cycle oil as a less expensive alternative to the lead replacement fuel additives. I have not heard of any rubber carb part issues using 2 cycle oils, the moonshine additives are far more destructive.

Dave
 
Just to back up what Dave said... I read about it after I asked what was the best fuel additive to help these old motors survive the ethenol. I tried it and I have to say, it works and has already loosened up a tight valve tappet I had on the driver side. Overall my 383 is a whole lot quieter now up top

The preferred mix is 1 ounce to every 5 gallons.
 
In a perfect world you could run a modern carb with an electric choke, but then you would not be in original condition.

Dave

I had considered this, and I do remember the conversation we had regarding my heat riser. If my carb wasn't original, I would definitely change it out. But it is...so I have to work around this issue. I can also adjust the divorced choke thermostat a little learner. Maybe that will help a little.
 
Using 2-cycle oil for an "upper cylinder lubricant" rather than a fuel additive designed just for that purpose? Or instead of Marvel Mystery Oil? How'd that oil/gas mix loosen a tappet, inside the motor? Hmmmmmm BTAIM

The carb heat shields were popular in the earlier '70s, as an alleged "fix" for hot fuel handling issues. As in after a "hot soak restart" situation. Holley had one for square bore carbs and one for spread bore carbs. GM even had some numbers for similar. I think they were more "band-aid fix" than anything, IF they worked.

Tried one of the Mr. Gasket stacks of gaskets and alum plates. Cracked the base of the 4732S on my '70 Monaco in carefully torqueing it down. Right by the vac advance port! End of that experiment!

Use an OEM-style "thick" base gasket with the inserts in the stud holes so you don't compress it too much. The best option, from my experiences.

On a divorced choke mechanism, the carb height has to match the length of the rod from the thermostat, period. Which is why the changes were made to the rod between the choke thermostat and the carb choke lever. That "U" in the vac pulloff link seems a bit too tight, to me.

It's normal for the choke thermostats to tighten with age, which means that to get them set right, it might be a notch or so leaner than the orig factory spec, from my experiences.

With the carb, engine, and everything under the hood at an ambient 70 degrees, the choke plate should just close, easily. Adjust the thermostat to get that to happen. Then, get a wide flat-blade screwdriver and insert it into the "U" on that pull-off link, widening it to pull the choke plate open the specified amount.

Getting exhaust heat to the carb base/choke thermostat area is critical for correct choke operation. Getting the choke "off" as soon as possible is the way I like for things to happen, no matter if it's the OEM divorced set-up or an integral electric choke. Which is why, as emission regs tightened, Chrysler went to a stainless steel cup for the choke thermostat to reside within, rather than the prior cast-iron home it had in prior model years. Which ALSO means that the heat crossover passage in the intake manifold MUST be clear of significant accumulation of "coke" so that the exhaust gasses can traverse that area, as designed.

Look in the FSM and you can see some pictures of how the carb choke linkage should be "bent" from the factory. Perhaps you can carefully re-configure things to that earlier configuration?

Might need to pull the plugs and clean them off for good measure, too.

Enjoy!
CBODY67
 
I’ve been running the marine 2 cycle consistently for several years now, since it was first(I think) mentioned on this site probably to the tune of 15k miles and that system has been trouble free since. It is supposed to go towards negating the affect of the ethanol and I haven’t had to clean any gelatinous smuts out of a carb in as many years so I’m a fan.
 
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