Topic: 20R w/ water choke high idle problems after warm up

[Yota87Truck]

I am not very familiar with carbs and am trying to get my 78 running with a 20R in it.  It runs well until it gets warm and then the idle goes up pretty high (no tach though).  After looking at the problem it looks like it is being caused by the water choke.  If I move a lever by the auto choke it will lower the RPMs.  I have done some googling but haven't found much.  Can anybody point me in a direction or knows where I can find a manual or diagram for the 20R carb?  It does seem to be running rich and I would like to fix that issue also.

Thanks

[H8PVMNT]

I would just rebuild it and take that water choke apart and clean it up.  I had the same trouble with mine and it ended up having an o-ring stuck in between to of the parts so that vapors and fuel could just kind of get sucked right from the bowl into the carb.  It wouldn't idle below like 2,000 rpms. I guess the previous owner was drunk when he rebuilt it the first time. Oddly, it got better milage when it was screwed up...

I've been able to get it to idle reasonably now.  Honestly though it always seems a little rich, especially at idle and while warming up.  I think it's because of the smaller CFM of the 20r carb because it can't get quite enough air for the amount of fuel.  A properly working 20r carb is awsome at angles off road though.  I can practically be on my side and it still runs.  Vertical inclines are no problem either.

As far as a manual, the re-build kits come with a pretty good diagram and a haynes manual shows how to set the idle mixture and such.

[kneedownnate]

Is the choke all the way open when it's warm?  If it's adjusted too tight and not allowed to open up, it will idle high and run rich.  I have a water choke and have it adjusted to barely close when warm and don't have any issues with it.

[79coyotefrg]

I am not very familiar with carbs and am trying to get my 78 running with a 20R in it.  It runs well until it gets warm and then the idle goes up pretty high (no tach though).  After looking at the problem it looks like it is being caused by the water choke.  If I move a lever by the auto choke it will lower the RPMs.  I have done some googling but haven't found much.  Can anybody point me in a direction or knows where I can find a manual or diagram for the 20R carb?  It does seem to be running rich and I would like to fix that issue also.

Thanks

the Haynes manual has some good diagrams and instructions BUT  I would ditch the stock 20R carb and get the adapter to run a 22R carb on the 20R intake.   that with a 22R stock exhaust manifold will really open that 20R up so it can really shine.
assuming you are in Cali,  if not get a weber
the stock 20R carb is only 190 cfm

[kneedownnate]

Why?  I'm in california and have a weber that I'm about to throw at a hobo, just as soon as I get the lce adapter to mount the much more reliable and less finicky 22r carb.  Webers are simple, but it seems their simplicity may be their undoing.

[79coyotefrg]

Why?  I'm in california and have a weber that I'm about to throw at a hobo, just as soon as I get the lce adapter to mount the much more reliable and less finicky 22r carb.  Webers are simple, but it seems their simplicity may be their undoing.

[Yota87Truck [OP]]

X2

I don't know why people are so adament about the weber.  They either hate it or love it...  I will try to get my stock 20R carb to work then if that doesn't work I'll decide from there wheither I go to the 22R carb or a weber.

[79coyotefrg]

X2

I don't know why people are so adament about the weber.  They either hate it or love it...  I will try to get my stock 20R carb to work then if that doesn't work I'll decide from there wheither I go to the 22R carb or a weber.

stock 20R carb -- 190cubic feet per minute
stock 22R carb -- 320 cubic feet per minute
3236 weber ----- 326 cubic feet per minute

[Yota87Truck [OP]]

stock 20R carb -- 190cubic feet per minute
stock 22R carb -- 320 cubic feet per minute
3236 weber ----- 326 cubic feet per minute

MPG, reliability differences?

Sounds like the 22R carb is the best option to go.  I am definitely looking to go the cheapest route for now.  And I am very much a virgin when it comes to carbs.  As far as the easiest short term option it sounds like the weber is the best, but also the most expensive.  Also sounds like the 20R carb is the cheapest and most difficult and not super reliable.  And sounds like the 22R is reasonably inexpensive but requires some knowledge.  But that's from the info I have found.

[IronClad]

22R carb by far. most reliable and with a couple little tricks can be made to run extremely well off road. Almost everyone i know that has had a weber has gone back to a 22r carb if they didnt swap for efi.

[H8PVMNT]

The 22r carb is probably better all around, I'm just weird and wanted to mess with the 20r carb.  It is too small, which is probably why it works so well off camber.  One day I'd like to try a holley truck avenger on it with a nasty cam...

[kneedownnate]

22R carb by far. most reliable and with a couple little tricks can be made to run extremely well off road. Almost everyone i know that has had a weber has gone back to a 22r carb if they didnt swap for efi.

Nope   You're wrong!  Webers are better than 22r carbs cause... cause...

Same here, if you actually drive your rig anywhere with the weber you'll hate it, especially when you tune it to one elevation then go to another.  I'll take low maintenance from a carb that flows 1 cfm difference any day.

[IronClad]

YA WELL!..  btw one of the guys in KOH finished the race running a carbed 22r/20r with a 22r carb =)  thats 180 miles of grueling dez racing