Vintage Oldsmobiles Curved Dash, Limited Touring, Models 40, 53, 66; Series 60, 70, 90

1956 - Replace or Rebuild the Carb?

Old January 24th, 2019, 06:23 PM
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1956 - Replace or Rebuild the Carb?


I am having hesitation issues and figured I'd rebuild the carb on my 1956 88. I just got the 88, so I had not been through it all yet. I took off the air cleaner, and someone installed a manual choke. So, now I am wondering if I should rebuild the carb (I don't know where to get the parts to revert to the auto-choke), or should I just buy a refurb carb. I was looking forward to the rebuild, but I'd rather not embark on a pointless exercise. Any suggestions?
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Old January 25th, 2019, 05:30 AM
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I would try a rebuild not sure about the auto choke but I don't mind a manual choke. You might want to take it apart to check the condition of the unit. I have had good luck with the rebuild kits I have bought for Mopars at Mike's Carb
https://www.carburetor-parts.com/Roc...ds_p_1523.html
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Old January 25th, 2019, 06:17 AM
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I would keep the original carburetor because replacements may or may not be correct, or actually in good condition. How about buying a second carb and eating the core charge so you can keep your original carb?
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Old January 25th, 2019, 07:01 AM
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Hesitation, if your referring to a dead spot when you step on the gas is usually due to accelerator pump issues. Air is faster than fuel so when you step on the gas there is a delay in the main metering system so the accelerator pump gives a squirt of gas to compensate for this. Most likely the pump cup is bad or the check ball is stuck. Some times there is wear on the pump rod hole on the pump arm. If there's slop in the rod and arm then this can cause hesitation as well. This is really common on high millage early rochester carbs like the 4gc's. Later they went to hardened pump arms. The fix is a new arm or weld up and drill new hole.

You can get kits from Daytona Parts company in Florida. They are good American made kits, no overseas junk.

Hope this helps.
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Old January 25th, 2019, 07:08 AM
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If the carb hasn't been rebuilt in a long time it may even have a leather pump cup. I'll also point out that ethonal is real carb killer especially if you live where there is big temp changes between seasons and the car is kept in non heated conditions. Condensation gets absorbed into the ethonal. Then as the ethonal evaporates the water settles to the bottom. Besides being hard on rubber parts it can cause serious corrosion issues. You can get ethonal resistant parts, but I always recommend getting RV ethonal free gas if you can. At least if it's going to sit for an extended time.
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Old January 25th, 2019, 07:56 PM
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I'd rebuild what you've got, those are pretty easy and straightforward to build. The manual choke looks like one of the better set ups, most fall apart or strip out. The auto-choke stuff is available at Fusick, and probably Rock Auto. The biggest issue with one of those is whether or not the stove in the intake is still useful or if it's been burned through.
If there's any advice I can give you about overhauling a 2GC, it's be very careful and aware of where the check-ball goes, I dropped it down the wrong hole, and ended up having to go for another carb, because the ball is not magnetic and wouldn't come out. (It fits under a "T" shaped tab with a pen-spring on it.) You'll know what I mean when you see an exploded diagram of one.
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Old January 25th, 2019, 09:18 PM
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Originally Posted by GlennC View Post

I am having hesitation issues and figured I'd rebuild the carb on my 1956 88. I just got the 88, so I had not been through it all yet. I took off the air cleaner, and someone installed a manual choke. So, now I am wondering if I should rebuild the carb (I don't know where to get the parts to revert to the auto-choke), or should I just buy a refurb carb. I was looking forward to the rebuild, but I'd rather not embark on a pointless exercise. Any suggestions?
You've got a lot of good advice so far. It looks like a 2GC Rochester. if it's original to the car the number will be 7007223 for Hydramatic and manual transmissions; 7008800 for Jetaway; 7009300 for a Jetaway service carburetor. Check the tag. If it is original, I would retain it and rebuild it. The Oldsmobile shop manual for 1956 has 12 pages with photos covering the 2GC carburetor. The choke can be restored to automatic or left as a manual. If you know how to operate a manual choke, I'd leave it as a manual. Reliability and performance are better. As mentioned, hesitation is often due to a shortfall with the acceleration pump. If you know how to do a rebuild, you will probably get better results than buying a commercially rebuilt carburetor. Fusick has the kit @ $59 + shipping. You might do a bit better on the cost elsewhere if you can find it.
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Old January 26th, 2019, 08:47 AM
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I use this guy... https://quadrajetparts.com/accelerat...c-104_109.html.. but a bunch of others are out there. It's a very common carb used on many different makes and models of cars with just little differences from model to model.You might as well try and do a rebuild yourself. You will learn a lot and save yourself quite a bit of money...... Tedd
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Old January 26th, 2019, 08:58 AM
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This is a tutorial on rebuilding a four barrel 4GC .
The principles and methods are the same :
https://classicoldsmobile.com/forums...-4gc-carb.html
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Old January 26th, 2019, 05:31 PM
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Thank you everyone! Very helpful! I feel incredibly lucky that you folks are out there and willing to help a newbie like me.

I am rebuilding the carb. Ordered the kit from Fusick, and it will be here this week. I went ahead and took the carb off the manifold and found a few things:
- No gasket between the carb and the manifold
- Vacuum line was completely blocked
- The long screw with a spring (forgot what it is called) is frozen
- Lots of build-up in the carb
- The gas that was in the carb was darker than it should be, so I am checking what is in the tank. Also, after the residual gas dried, there was a fine grit in the carb

On a related note, the oil bath air cleaner has no oil in it, and I cannot get it apart to clean it or replenish the oil. I looked in the shop manual, and found no instructions on servicing the cleaner. It just said to do it and fill with 40. I have not been able to find a video on YouTube. Anyone have any pictures of how these come apart or other advice?
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Old January 27th, 2019, 06:44 AM
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Originally Posted by GlennC View Post
Thank you everyone! Very helpful! I feel incredibly lucky that you folks are out there and willing to help a newbie like me.

I am rebuilding the carb. Ordered the kit from Fusick, and it will be here this week. I went ahead and took the carb off the manifold and found a few things:
- No gasket between the carb and the manifold
- Vacuum line was completely blocked
- The long screw with a spring (forgot what it is called) is frozen
- Lots of build-up in the carb
- The gas that was in the carb was darker than it should be, so I am checking what is in the tank. Also, after the residual gas dried, there was a fine grit in the carb

On a related note, the oil bath air cleaner has no oil in it, and I cannot get it apart to clean it or replenish the oil. I looked in the shop manual, and found no instructions on servicing the cleaner. It just said to do it and fill with 40. I have not been able to find a video on YouTube. Anyone have any pictures of how these come apart or other advice?
I'm "assuming" that you have the automatic transmission. There should be two carburetor to manifold gaskets; one above the "bracket" and one below. They "might" be in the kit. The part number is 568039.

You may have to drop and flush the tank. Check for corrosion. While it's out you may want to re-calibrate the gauge sender and add an extension to the fuel pick-up tube. Oldsmobiles in the 50s had a way of "running out of fuel" with 3 or 4 gallons remaining in the tank.

I don't know why the oil bath air cleaner will not "come apart". It seems like the same wingnut/stud holding it to the carburetor held it together. ????????

Last edited by Ozzie; January 27th, 2019 at 07:11 AM. Reason: clarification
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Old January 27th, 2019, 07:15 AM
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On a related note, the oil bath air cleaner has no oil in it, and I cannot get it apart to clean it or replenish the oil. I looked in the shop manual, and found no instructions on servicing the cleaner. It just said to do it and fill with 40. I have not been able to find a video on YouTube. Anyone have any pictures of how these come apart or other advice?

As Ozzie noted, the air cleaner should come apart easily to wipe it out and add oil. The filter element itself does not come apart. You need to soak the whole thing or spray it to clean it.
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Old January 27th, 2019, 07:45 AM
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Thanks Gents!

Great point on the extension to the fuel pick-up tube. I will be dropping the tank and flushing, so might as well service the sending unit and add the tube. I will also replace the fuel lines...might as well do that too.

I was able to remove the air filter unit from the carb via removing the wing nut...it's the oil bath housing that won't come apart. I am using penetrating oil to try to loosen up the crud on the oil bath. Hopefully, that will work. I found some pics of a disassembled oil bath filter for a 4GC, and translating that to my 2GC, I know the thing has to come apart. Fusick does have a 56 2GC refurbed oil bath on sale on ebay, but it actually does not look like completely like mine...and I'd rather not spend the cash.
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Old January 27th, 2019, 08:21 AM
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Don't forget to drain as much gas as you can out of your tank before you drop it. 3-4 gals of gas becomes quite heavy and awkward as you drop the tank especially if you are laying on your back underneath your car.... Just a thought.....Tedd
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Old January 27th, 2019, 09:13 AM
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I have been amazed a couple of times by cars would run with grossly abused carbs. I purchased an 1949 Chev 3100 that I had to scrape off shelac on the outside of the carb with a flat blade screw driver, before I could tackle it with carb cleaner..Tthe inside was no better over an 1\2 inch of fine particles in the float bowl. Previous owner said it would run for him.
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Old January 27th, 2019, 11:59 AM
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Originally Posted by GlennC View Post

I was able to remove the air filter unit from the carb via removing the wing nut...it's the oil bath housing that won't come apart. I am using penetrating oil to try to loosen up the crud on the oil bath. Hopefully, that will work.
I recall a similar problem with a '48 Lincoln . It had the same type air cleaner .
The solution was to soak the whole thing in kerosene in a bucket for a few days .
Loosened up the crud and it came apart easily .

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Old January 27th, 2019, 09:48 PM
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Originally Posted by Charlie Jones View Post
I recall a similar problem with a '48 Lincoln . It had the same type air cleaner .
The solution was to soak the whole thing in kerosene in a bucket for a few days .
Loosened up the crud and it came apart easily .
I'll second this idea. I used to soak my "stubborn cases" in mineral spirits. All you need is an appropriate sized container and enough solvent to submerge the air cleaner. Then just leave it for a while.
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Old January 28th, 2019, 06:12 AM
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Great point Tedd! I will probably make a support and use a floor jack for support during the removal. Thanks everyone for the tips on submerging the oil bath in kerosene...I'll be doing that this week. I found the penetrating oil seems to be making some progress, but trying to pry the bath apart will likely result in too much damage.
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Old March 3rd, 2019, 05:38 PM
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Carb Update

Rebuilt the carb! Bought the kit from Fusick, watched some videos on Youtube, read my manual over and over again, and got it done. Cleaning the thing took longer than pulling it off/apart and putting it back together with the new parts. It started right up...and it runs great!!! No hesitation, nice idle, smooth acceleration. Put a repro batwing air cleaner on...I couldn't get the oil bath cleaner to separate, and now I can use paper filters. It looks great. Thanks for all the advice everyone!
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Old March 3rd, 2019, 08:58 PM
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Congrats. You might consider converting to an electric choke. I think RockAuto has kits for that.
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Old March 5th, 2019, 11:28 AM
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Talking

Originally Posted by GlennC View Post
Rebuilt the carb! Bought the kit from Fusick, watched some videos on Youtube, read my manual over and over again, and got it done. Cleaning the thing took longer than pulling it off/apart and putting it back together with the new parts. It started right up...and it runs great!!! No hesitation, nice idle, smooth acceleration. Put a repro batwing air cleaner on...I couldn't get the oil bath cleaner to separate, and now I can use paper filters. It looks great. Thanks for all the advice everyone!
Great work. Always satisfying when you attempt and learn something new. Especially when it works.
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Old March 5th, 2019, 01:42 PM
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Originally Posted by redoldsman View Post
Congrats. You might consider converting to an electric choke. I think RockAuto has kits for that.
I agree with you Glenn. I put an electric choke in my '56 about 5 years ago, and I highly recommend it.
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Old March 5th, 2019, 07:42 PM
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Are you sure you have a 2gc carb. I didn't know that a repo batwing would fit on a 2 bbl carb, then again there is something new on the market every day...... Tedd
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Old March 10th, 2019, 03:08 PM
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Tedd...it's a 2GC. I had to buy an adapter that sits on top of the carb to accommodate the larger throat of the batwing, but it works great. The adapter is a Spectre Performance 4953 5-1/8" to 3-1/16" Air Cleaner Adapter. In case anybody is interested, I found it on Amazon:
Amazon Amazon

On the electric choke idea...anyone know where I can get one? I reinstalled the manual choke, but it really does not function all that well.
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