Author Topic: Guess that 20R carb part!!!  (Read 1942 times)

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jmac80

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Guess that 20R carb part!!!
« on: Jan 23, 2018, 08:43:03 AM »
Hi all-

So I am rebuilding the 20R carb and when I pulled everything out of dip I realized that there was a part I did not remember putting in there (or removing from the carb for that matter).  I've looked at diagram of my carb and don't see it (although it's on the autozone website and is a little fuzzy).  I'm beginning to wonder if it is something that was dropped in the linkage and has just been stuck in there and then fell out into the dip with the throttle body.  I tried to disconnect the minimal amount of linkage, so it's not like it was in a million pieces, just the normal 500,000 :smack:  Does anyone recognize the piece below?  One hole is threaded and the other is not and appears to be for a spring...maybe?

also, I also either lost along the way or never had (I'm guessing the prior) a spring that went into one of the check valves in the bowl.  I had a spare 20R carb from a different year or corolla or something (came in truck passenger seat upon delivery from eBay truck purchase, didn't argue) that I salvaged it from.  I would like to replace it in the other carb as it's been newly rebuilt as well.  Do you know if you can get something like that from a dealer or must it generally be salvaged.

OK, here's the part...
1980 long bed; 20R; L52; 3" OME; 30-spline Marfields; Marlin high steer; PS; AC

H8PVMNT

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Re: Guess that 20R carb part!!!
« Reply #1 on: Jan 23, 2018, 09:43:49 AM »
Yes I know what it is.  It's called something like "Hot Idle Compensator".  It resides on the back (driver's) side of the carb under a little zinc plated cover and has a small, flat o-ring under it.  The top gets screwed down and the bottom kind of spring loads against the little flat o-ring over a small hole with a slight recess the size of the flat o-ring.

This does something with your mixture at a certain temp range by opening a passage from the float bowl to something else.  Some carbs don't have them at all and the place is there in the casting but the holes are plugged up.  If yours has it you will want to use it.

On the spring, a cheap re-build kit should have the replacement.  I get the Napa kit and it replaces nearly all of the little springs and balls.
“I would rather wake up in the middle of nowhere than in any city on earth.”
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"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

jmac80 [OP]

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Re: Guess that 20R carb part!!!
« Reply #2 on: Jan 23, 2018, 10:38:25 AM »
Yes I know what it is.  It's called something like "Hot Idle Compensator".  It resides on the back (driver's) side of the carb under a little zinc plated cover and has a small, flat o-ring under it.  The top gets screwed down and the bottom kind of spring loads against the little flat o-ring over a small hole with a slight recess the size of the flat o-ring.

This does something with your mixture at a certain temp range by opening a passage from the float bowl to something else.  Some carbs don't have them at all and the place is there in the casting but the holes are plugged up.  If yours has it you will want to use it.

On the spring, a cheap re-build kit should have the replacement.  I get the Napa kit and it replaces nearly all of the little springs and balls.

Damn, I owe you a beer.  I see where you're talking about.  I kept looking at my before disassembly pics and wonder where the hell that thing went.  I don't remember taking the screw out, so I'm thinking it was just floating in there fell out when I pulled the cover off...screw probably was loose and fell out with it.  I should pay more attention to what I'm doing and stop working on the ground.  So here's the cover, and yes, it is shown on the autozone diagram.  Item 17.  What's the trick to getting that pump jet out?  I just left mine in and sprayed it out really well with cleaner. 

Well, my crappy rebuild kit only had one diaphram, no springs, and different style needle valve.  I bought it  a while back and don't remember where it came from, but at least the gaskets have all been correct so far.  I just reused all my old balls and washers, as opposed to the new balls and composite washers in the kit.   What do ya'll think about these different needle valves?  I'm wondering if the old one isn't wrong, don't those kind normally hang from a wire hanger deal?
1980 long bed; 20R; L52; 3" OME; 30-spline Marfields; Marlin high steer; PS; AC

jmac80 [OP]

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Re: Guess that 20R carb part!!!
« Reply #3 on: Jan 24, 2018, 10:52:33 AM »
Some carbs don't have them at all and the place is there in the casting but the holes are plugged up.

So I looked at thing a little more closely last night and realized, mine had been sitting in there backwards and not screwed in.  I can tell it was backwards because some of the zinc plating had transferred to my mystery part (you can see it in the pics above).  The side with the transferred zinc was obviously facing out but should be facing in.  Regardless of that and by chance, on the ones that have the holes plugged up are the screw holes for the zinc plate still there?  On mine, the plate is there (obviously from the picture), but the hole that would lead into the bowl is plugged up.  Also, the mystery part has threads in the top hole for a screw to hold it into the outer wall of the secondary's barrel.  The secondary barrel of mine has a small hole where the screw would go, but it's not nearly big enough and it's not threaded.  Do you think someone just stuck this in there even though it didn't need to be?  I also, checked my spare/salvage carb for a the screw and the mystery part was missing from it all together, just an empty cavity under the zinc plate.
1980 long bed; 20R; L52; 3" OME; 30-spline Marfields; Marlin high steer; PS; AC

H8PVMNT

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Re: Guess that 20R carb part!!!
« Reply #4 on: Jan 24, 2018, 11:02:28 AM »
The ones without this part that I have had have all the holes there but the hole that does something is plugged up.  They usually don't have the cover plate though.  Maybe try to blow through the hole with some carb cleaner and if it is truly plugged up then you can forego the part.
“I would rather wake up in the middle of nowhere than in any city on earth.”
– Steve McQueen

"Except for maybe Seattle."  -H8PVMNT

"I plan to hit 300k in this truck"  :)bestgen4runner

 "I'm jealous of your shop. It has concrete and doesn't smell like pickles like the old shop  "  300K

jmac80 [OP]

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Re: Guess that 20R carb part!!!
« Reply #5 on: Jan 30, 2018, 04:46:05 PM »
The ones without this part that I have had have all the holes there but the hole that does something is plugged up.  They usually don't have the cover plate though.  Maybe try to blow through the hole with some carb cleaner and if it is truly plugged up then you can forego the part.

When you say plugged, does it look like this?  The top hole for the screw is there, and the bottom is plugged.......I'm just patiently waiting for spring to show up in the mail.  My wife's patience is running out as I put up a card table in the den to map out parts, telling her it would be a day or two max.  We're going on about a week or so now....OOOPS
1980 long bed; 20R; L52; 3" OME; 30-spline Marfields; Marlin high steer; PS; AC

 
 
 
 
 

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