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There have been MANY hot idle compensator "types" used on the many various Rochester Quadrajets - more than I've witnessed. Many and I mean many remove the cover and the compensator for any of a variety or reasons. I personally have never had to make any adjustment(s) to any Quadrajet I've owned since mainly I don't know EXACTLY how to make the adjustment other than what I've read. I would not take it apart or remove it. I'll try to provide one link for you and you can research it's usage on your own.
When I pulled the airhorn off the tube on the far left was laying in the body. Not 100 percent sure it didn't fall out when disassembling but if it was already out what issues would that cause. Wonder if that was my problem perhaps.
Here is a direct quote & the URL link to the quote you can perform your own research. Good Luck!
The hot idle compensator is a thermostatically controlled valve that helps to prevent engine stalling when idling in very hot weather. Long periods of engine idle cause an excessive amount of vaporization of gasoline in the float bowl. These vapors will find their way into the carburetor throat and cause an overly rich mixture. The hot idle compensator consists of a bimetallic strip of metal which operates a valve that controls an air passage ending under the throttle valve. The bimetallic strip, which consists of two pieces of dissimilar metal with different expansion rates, will curl upwards as the temperature increases, opening the valve. This will, in turn, admit air under the throttle valve compensating for the overly rich mixture.
What are your issues? 1. The tube you described provides fuel to the air horn casting feed hole at the fwd. edge of the secondary air valve (flapper) & helps 4 barrel transition. 2. Cliff Ruggles recommends tapping & plugging the hole feeding the Hot Idle Compensator. Apparently it was a band aid fix but can cause idle problems if not working properly & was phased out.
What are your issues? 1. The tube you described provides fuel to the air horn casting feed hole at the fwd. edge of the secondary air valve (flapper) & helps 4 barrel transition. 2. Cliff Ruggles recommends tapping & plugging the hole feeding the Hot Idle Compensator. Apparently it was a band aid fix but can cause idle problems if not working properly & was phased out.
Maybe that is my problem. Doesnt idle consistently. When in gear and stopped at a light it acts like it loads up and rough idles. Put it in neutral and clear it out it gets better short stop signs meanin stop and go no real issue. Basically it seems to act and smell like it runs rich. At idle. I have set AF screws but that didn't help at all. Under throttle it works great. Just idle problems mostly in gear.
I’ll note based on images yours is installed upside down. You’ll hurt nothing, could make an improvement. Remove cover plate, is the bimetal actually inside? Many get removed and cover plate still exists. Turn it right side up and try it. Remove bimetal completely and try it. You aren’t going to hurt a thing. Experiment, clean it. Test it out. Nothing ventured nothing gained.
One of the best things to do tearing down a carburetor is take a crap load of pictures. Every single step. There are so many screws etc. That helps so so much.
Check for primary nozzle drip at idle, you may need a flashlight. This can be caused by high float or too much fuel pressure.
Another check is to remove the carb & invert it. Check closed throttle blade position. If not closed you may be compensating for some other problem like too little timing or insufficient idle air/fuel delivery. Idle tubes can get clogged.
When I pulled the airhorn off the tube on the far left was laying in the body. Not 100 percent sure it didn't fall out when disassembling but if it was already out what issues would that cause. Wonder if that was my problem perhaps.
Yes, that will definitely cause an issue. I had that happen to my carb back in the 80s and the engine did not run well at all. Luckily it's very easy to tap the tube back into place.
I used to rebuild all sorts of crazy carbs back in the day and when in doubt i would use the old method of counting the turns. I would turn the screw in, after a bit of lube, and count the turns precisely until it stops and make note. I would then disassemble for cleaning and put it back exactly like it was.
With the wonder of the internet now you can at least reach out like you did to find out what it is. After the rebuild you can adjust said part if you learn it relates to something you are targeting for improvement.
Carb worked better after the rebuild. Actually ran on the choke as it should.
Couldnt finalize tuning AF screws cause the hot air stove pipes on the manifold are leaking at the base. Tried to seal it up but didnt work. Ordered a block off plate and still need to find an electric choke. Question I have is where did you tie in the wire for the electric choke? I know its needs to be a hot only when keyed on but if you can give me a specific spot you use that would be helpful. What size wire is recommended for the electric choke?
Without knowing your wiring layout i would be throwing spaghetti against the wall. It just needs to be a 12v source with the key on like you said. Hate to cut into a nice clean harness but you need the power from somewhere. Look for any place there is already a break in the harness and tie in there. I suppose you could also run a wire back to the fuse box to a keyed 12 volt source by itself if you don't want to cut. in. Likely some of the smarter folks here can offer a factory correct location to tie in.
What is this thing on the back with the spring for? Haven't seen it any videos I watched.
And once again, the reason why, rather than watching ZooTube videos, you should actually READ the factory Chassis Service Manual. Olds spent a lot of effort to provide detailed information on how the various systems of the car operate. Not only does this help you understand what everything is, but by understanding the theory you frequently have a better feel for troubleshooting problems.
Carb worked better after the rebuild. Actually ran on the choke as it should.
Couldnt finalize tuning AF screws cause the hot air stove pipes on the manifold are leaking at the base. Tried to seal it up but didnt work. Ordered a block off plate and still need to find an electric choke. Question I have is where did you tie in the wire for the electric choke? I know its needs to be a hot only when keyed on but if you can give me a specific spot you use that would be helpful. What size wire is recommended for the electric choke?
The choke heater tubes leaking shouldn’t have any impact on setting the idle air/fuel ratio. The air bleed in the choke is the same whether the tubes are intact or not.
I would recommend replacing the heater tubes instead of installing an electric choke.
If you must run an electric choke, it can be powered from the IGN terminal in the center of the fuse block.
...where did you tie in the wire for the electric choke? I know its needs to be a hot only when keyed on but if you can give me a specific spot you use that would be helpful. What size wire is recommended for the electric choke?
Read this thread before deciding where to wire the electric choke >>> Electric choke wiring
The choke heater tubes leaking shouldn’t have any impact on setting the idle air/fuel ratio. The air bleed in the choke is the same whether the tubes are intact or not.
I would recommend replacing the heater tubes instead of installing an electric choke.
If you must run an electric choke, it can be powered from the IGN terminal in the center of the fuse block.
How can you set AF by vacuum with a big vacuum leak on the manifold where the tubes go through?
The broken tubes do not create a vacuum leak. The tubes channel air in from the back of the carb, through the U tube heater in the exhaust crossover, then into the carb through a VERY small port behind the choke coil housing. This vacuum bleed will be the same with intact tubes connected, tubes with holes, and even with no tubes connected at all. The “vacuum leak” is the same in all these situations and as such the AF setting is unchanged
The broken tubes do not create a vacuum leak. The tubes channel air in from the back of the carb, through the U tube heater in the exhaust crossover, then into the carb through a VERY small port behind the choke coil housing. This vacuum bleed will be the same with intact tubes connected, tubes with holes, and even with no tubes connected at all. The “vacuum leak” is the same in all these situations and as such the AF setting is unchanged
The leak isnt a hole on a tube but is where the tubes go throw the plate on the manifold. When I hit this area with carb cleaner rpms came up. The tubes go through the plate on the manifold so if it is leaking at that plate on the manifold isnt that a vacuum leak?
The leak isnt a hole on a tube but is where the tubes go throw the plate on the manifold. When I hit this area with carb cleaner rpms came up. The tubes go through the plate on the manifold so if it is leaking at that plate on the manifold isnt that a vacuum leak?
The tube that goes into the mainfold is a closed loop. More importantly, it is in the EXHAUST crossover, not manifold vacuum. If spraying there changes idle, they you are inadvertently also getting carb cleaner into the real leak, which is likely the base gasket.
The tube that goes into the mainfold is a closed loop. More importantly, it is in the EXHAUST crossover, not manifold vacuum. If spraying there changes idle, they you are inadvertently also getting carb cleaner into the real leak, which is likely the base gasket.
When you say base gasket are you saying the carb base or this plate gasket?
Great. its brand new gasket with the carb rebuild.
Again, I'm just guessing. Is the carb tight? Is the base warped? Have you tried spraying around the carb to see what happens? One more time: that choke heater plate is NOT the source of a vacuum leak. It isn't physically possible.
It may not always be possible to detect minuscule vacuum leaks - e.g. vacuum leaks which don't contribute to a significant performance issue; yet, significant vacuum leaks which contribute to performance issues are readily witnessed with a vacuum gauge. What is the current measured vacuum? Importantly, the vacuum should be "steady".
Go figure. I went out to investigate more and it starts up with no leaks detected anywhere. Maybe the first heat and cool down cycle sealed up? Anyway, I set the AF and it seemed to run decent. Steady 16 on the gauge. I guess Ill keep running it for a while and see how it goes for a while. Ran it down the highway and stomped it down for 4 barrels and all seemed to be good.
Only thing I noticed today was when I did the cold start the choke wasnt all the way on the highest cam. It was on the second notch. When I hit the throttle it didnt come up to highest part of the cam. I could push it up and get it to stay there and it starts good and runs on choke. Does this mean I need to adjust the choke more or the high speed screw?
Only thing I noticed today was when I did the cold start the choke wasnt all the way on the highest cam. It was on the second notch. When I hit the throttle it didnt come up to highest part of the cam. I could push it up and get it to stay there and it starts good and runs on choke. Does this mean I need to adjust the choke more or the high speed screw?
The choke isn't supposed to be fully closed if the air temp is warm. That means the fast idle cam won't be on the highest step either.
July 20th, 2023, 03:03 PM
