Carburetor operation & repair information

[SlantSixDan]

Here is the Holley 1945 operation and repair manual (pdf), and here is the Chrysler training film on the Holley 1945.

Here is the Holley 1920 operation and repair manual. Discussion threads about 1920 repair are here, here, and here, and there's a big discussion thread about 1920 modification & upgrade here.

Here is the Carter BBS operation and repair manual (pdf)

Here is the Carter BBD operation and repair manual (pdf)

There is a Chrysler training movie on the Holley 2280 over here.

This site has a choke and carburetor adjustment article with links to carburetor-specific information here.

Additional Chrysler-made movies related to carburetors can be found here, and more paper documentation can be found here.

Setting the idle adjustments

There's no spec for where the mixture adjustment screw should be in terms of turns in or out, so don't follow advice that starts and ends with "Set the mixture screws two and a half turns out". If you don't have an exhaust gas analyser, which most of us don't, and you're not using a ColorTune glass spark plug to set the mixture by the appearance of the combustion flame (buy one here or here), then the best you can do is to adjust by engine behaviour.

If you're starting with a freshly installed carburetor or the idle mixture is way off, first turn the mixture adjustment screw(s) clockwise until they lightly seat — don't turn them down tight, or you'll spoil the carburetor — and then back the mixture screw(s) out anticlockwise 2½ turns. This is not the final adjustment, it's just getting the screw(s) into a position near the right ballpark so you can find the right adjustment.

Make sure the ignition system and PCV system are all in good shape, plugs and PCV valve are clean and working correctly, ignition timing is set correctly, and valves are adjusted. Get the engine thoroughly warmed up, all the way up to full operating temperature, connect a tachometer, and then you're ready to work with the idle speed and mixture adjusting screws.

Use the curb idle speed adjusting screw (the one that doesn't seat on the fast-idle cam) to set the idle speed to between 600 and 750 rpm. Then, go round the other side of the car and adjust the mixture screw(s) clockwise ¼-turn at a time, slowly, pausing for a few seconds after each ¼-turn, until the engine just begins to drop RPM because it's too lean (you can use your ears to detect this, but watching the tachometer helps). Then, turn the mixture screw(s) back anticlockwise ¼-turn at a time or so, again working slowly and pausing, and keeping careful track of the number of ¼-turns, until the engine just barely begins to drop RPM because it's too rich. Then, you turn the mixture screw(s) clockwise half the number of quarter-turns you counted between lean fall-off and rich fall-off, and that's your final adjustment. Then re-check the idle speed and readjust to 650 rpm (use the tachometer), and you're all done setting the idle mixture and speed. You want the final adjustment of the screw(s) to be in a clockwise direction, so spring tension doesn't change the adjustment over time.

Sometimes you will not be able to find the rich dropoff point, because the carburetor is designed not to permit an overly-rich idle mixture. In that case, the best you can do without an exhaust gas analyser or ColorTune is to find the lean dropoff, then carefully back the mixture screw(s) anticlockwise just 1/8 turn at a time until the speed stops increasing (watch the tach!), then clockwise ¼ turn. Then use the idle speed adjusting screw to adjust back to between 600 and 750 rpm, and you're done.

On a carburetor with two idle mixture screws — many but not all 2bbl and 4bbl carburetors — it's important that the mixture screws be kept in sync.

Cold-engine start & stall issues

Cold-engine hard-start, stalling and rough running issues are usually choke-related; an electric choke kit is often a wise choice if your present choke thermostat is old or faulty, and the carburetor's choke pull-off may need adjusting. Choke adjustment information is here.


General advice

Always avoid "remanufactured" carburetors for the reasons discussed in this thread.

Problems that seem to be carburetor-related are often alleviated by doing the fuel line mod.

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一期一会

By birth & parentage: US citizen, 2nd class
By choice: Canadian citizen, 1st class

[Red]

Very cool. Thanks much, Dan.

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obliquely-inclined state of mind

[sixertrk]

My goodness, how great is this, remind me to enter your name in the next automotive "Jeopardy" match!!

[dusterguy225]

Yes thank you, I printed the whole BBD one out when you pointed me to it not too long ago. It will definatly come in handy!

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels

[Aggressive Ted]

Awesome info.......! Thanks

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live.com/self.aspx/74%20Dodge%20Dart%20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, ram air, electric fans, 2.5" HP2 & FM70 exhaust, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

[Rug_Trucker]

Well the BBD videos sure were informative. And it was a pleasent surprise to see "Sam" had such a nice butt!

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'72 Duster 198 stock cam, 3:23's Hookers

'74Fart Dart

'79 Maxivan 360 Offy Qjet Comp RV cam
93 D350 160HP Cummins Auto Dually Clubcab
93 Corolla

[Brian]

Dan, Thanks for posting the link for the videos.... Awesome!

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[Rug_Trucker]

Think there would be interest in a BBD tech sticky? I have been documenting differences between Super6 and 318 BBD's with pics. Just some trial and error things I have been doing in the shop.

Let's face it there is lots of them out there, and they are cheap!

I am actually thinking about rebuilding them for extra cash. That is a while off from now. I need the proper stuff and tools to bush the shafts.

Don't know if I would be able to handle the flaming if something went wrong with somones rebuild...........

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'72 Duster 198 stock cam, 3:23's Hookers

'74Fart Dart

'79 Maxivan 360 Offy Qjet Comp RV cam
93 D350 160HP Cummins Auto Dually Clubcab
93 Corolla

[daniel_depetro]

Wow, awesome information.

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1969-1/2 Dodge Super Bee A12 (440 Six Pack, 4-spd, Dana 60)
1974 Plymouth Duster 360 (4-spd, 8.75")
1973 Plymouth Duster (225, auto, 8.25")
2001 Dodge Ram 1500 QC 2wd (5.9L, auto, Dana 60)

[Force Fed Mopar]

[SlantSixDan]

[Force Fed Mopar]

So you're saying a baseplate from one carb will work on another that used a different gasket between the body and baseplate? When you buy a crb kit for a BBD, it usually has at least 2, sometimes 3 different gaskets for the baseplate. Maybe I should take pics of all my pieces and post them, see if you can can see any differences. Whatever combination I put together it will start, but then die, unless you keep pumping the gas. Rev and hold it, it will stay revved for a few secs, then try to die. Acts like it isn't pulling fuel out through the boosters.

I guess as far as rebuilding goes, rebuilding and remanfacturing are two different things in my mind. Rebuilding is simply tearing down, cleaning, replacing gaskets, needle and seats, floats, accel pumps etc. Remanufacturing would be totally dismantling, bead blasting, rebushing, polishing etc, then installing all new gaskets and stuff.

BTW are there any part numbers on the individual pieces that can help identify what version of what model?

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Rob M
'80 D100 SWB stepside, S6 4-spd OD

[SlantSixDan]

[Force Fed Mopar]

Yeah I read the link, but mine all have clear passageways and whatnot. They just don't match up, they are like 1 old kind (w/ the skinny wire metering rods and small jets) and 2 newer ones (w/ the larger rods and same jets as AFB's). But I think even the 2 newer ones had different base plates, I need to look again. Been a while since I looked at them, and I recently found that the engine I was trying to get them to work on (S6 2bbl in my '80 D100) had a vacuum leak at the EGR valve mounting surface due to a cracked EGR. Seems like I tried them on my V8 too though, I dunno. I need to go through them again.

BTW I have a bunch of pics I took of the difference pieces in two "identical" BBD reman's, if Rug Trucker or whoever is interested in them for documentation.

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Rob M
'80 D100 SWB stepside, S6 4-spd OD

[valiant effort]

This might be a stupid question but I am sure I have many others. *L Anyway, what exactly is the difference between remanufactured and rebuilt?

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If only I had the time to do what I want to do instead of what I have to do!