The Stovebolt Site Forums The Shop Area Engine Shop any major Gotchas on Rochester B carb?

I am about to embark on a carb rebuild, anything I should know before i start?

Tag:7002050 JO
Throttle body:7002105PF in big letters KF8

I haven't gone for a rebuild kit. what will I need that doesn't come with the kit (any additional gaskets?) am I likely to find this at NAPA, or do I need to look somewhere online? any difficult to dis-assemble or re-assemble parts?

thanks in advance for any tips.

-Mike R.

The whole carb is a gotcha. Sure, you can rebuild it but, it's always gonna be a Rochester 1 bbl.

The kit should have everything you need. I had to go buy some gasket material 'cause the top section of housing was slightly warped on mine, no idea why. Had to double up on gaskets. It's a pretty straightforward rebuild, easily done following the instructions.

Napa may have it. Think I got mine thru Autozone.

David
Kustoms-and-Sleds

I have rebuilt a few. The most common problem is a warped air horn gasket surface. The second worst is the small float size, which doesn't provide much pressure to the needle valve so it tends to hang up. I found that using a steel ball bearing and a punch to round out the seat really helps with the life of the needle valve. (Thanks for the tip carbking).
The final problem I have run into is the power piston sticking. It needs to be clean, and if it is tarnished hit it with some brass polish to clean it up so it slides nicely. (This is a common problem with qjets and 2G's too)

Another problem with all Rochesters is throttle body wear at the throttle shaft. Usually needs to be sleeved.

If the carb doesn't need major work, you can rebuild them blindfolded after you've done a few. Kits are very generic anymore, last one I got had a modern accelerator pump, which wouldn't work. Couldn't by a new pump locally, either.

The kit I got from Carquest did not have the accelerator pump. I had to scrounge through my old carbs and find a good fit. Better, just not perfect.
Ralph

hrmm...

so it sounds like the accel. pump is not likely to come with the kit... that will make this more difficult... as this carb hasn't moved in a while, and the pump is certainly shot.

what would a reasonable replacement carb be, one that I could rebuild myself (ie. has all the parts available) and hopefully find a core in the boneyard, I have heard many mentions of the Carter YF, but not many good, what is a good match for a bone stock 216?

-Mike R.

My kit came from American Classic and included the pump. It was about $18 plus shipping. BUT my carburetor is still not right. (it's not the kit but the mechanic I'm sure) My engine is running way too rich. I'm suspecting a stuck power valve.
I also had the float stick and run gas out everywhere.

I have never seen a kit for one of these, that did not have a pump.

This fall, I picked up an original GM technical booklet on the "new Rochester B and BC " for 1952. It explains the workings of all the different circuits and explains how to rebuild it. If this site or someone would like to host the files, I can scan it.

I found a rebuild manual in the old-manual project... Car Manuals

-Mike R.

I dis-assembled last night, and I think I have a salvagable unit. now I just need the rebuild kit..

All the kits I've gotten from NAPA included a pump and everything else you will need. Save the old air horn gaskets as you may need to double up on them. Also, get a Mic to set the float level with, haha. These carbs are a lot more sensitive to float level than most. The gauge in the kit is just a starting point. Set it, run it and check the plugs, a little float level off either way and they will be white or black. Welcome to the world of Rochchester B's.

Question - What do all of the following items have in common?

(A) Carter YF Chevrolet replacement carb
(B) Stromberg BX series Chevrolet replacement carb
(C) Zenith 228 series Chevrolet replacement carb
(D) Carter W-1 1946-48 Chevrolet original carb
(E) 15 year old boy pouring gas into the engine out of a boot

Answer - They all provide more reliable carburetion than the Rochester B!

The Rochester B has a major problem, and several others which have been created by Dr. Goodpliers (Mr. Goodwrench's evil twin ). The major problem (as mentioned earlier in this post) is warped castings. Rochester used only 4 screws to hold the airhorn (top casting) to the bowl center casting). 8 should probably have been used. Clean the castings, then assemble the airhorn to the bowl WITHOUT a gasket, and hold so that the assembly is between you and a lighted light bulb. If you see light, the castings are warped.

The correct way to solve this problem is with an oven and some simple jigs which are easy to make. Using a feeler gauge, measure the distance between the two castings. After placing the assembly in the jig, tighten the jig to remove 0.003 as measured by the feeler gauge. Heat the assembly in an oven at 400 degrees F. for 1 hour. Allow to completely cool. Repeat this process until the castings are true.

The induced problems occur because the commercial rebuilders interchange parts on these carbs with no regard to jetting or the pressed-in airbleeds (different for different years, car or truck, transmission type, etc.).

The fact that your carb does have a tag may mean Dr. Goodpliers has not yet seen your carb, and if you don't mind caring for the warpage, it may be useable after a rebuild.

If looking for a kit, take the number from the tag AND YOUR OLD ACCELERATOR PUMP with you to the parts house. The cheaper kits will not have a pump - avoid. The better kits will have a pump BUT IT WILL BE THE INCORRECT NEWER STYLE PUMP - avoid. Your pump is the old style where the top stem of the pump is flat metal with a retangular slot. The pump arm is inserted through the slot and held in place by a spring. The new style pump has a round stem with the pump arm sliding over the stem. They are not interchangable!!! Since the kits are packaged with a see-through cover, make sure the pump in the kit is like your pump.

The best kits will contain the correct pump, as well as the correct main jet, power piston spring, power valve, etc.

If you have difficulty acquiring a suitable kit locally, there are specialty companies which produce such kits. They are available.

With all due respect to the gentleman who posted about the sensitivity of the B to float settings; ASSUMING THAT ALL PARTS IN THE CARB ARE UP TO PAR, THE B IS NO MORE SENSITIVE THAN ANY OTHER TO FLOAT SETTINGS. Set it to specification, and it will work!

Other parts that should always be replaced when building a B are the power valve (plug, small spring, and ball) and the power piston spring (long spring under the power piston). The power piston spring is a tensioned spring, and fatigues. This is the control for the power valve (or economiser valve if you are a Holley fan). A fatigued spring will give unpredictable results.

If you address all of these issues, the B is a very simple carburetor, and rebuild should give a few years service before going through the entire procedure again!

Personally, I would go with the YF replacement or one of the others mentioned in the "question" (even the 15 year old)

Jon.

Addressing other comments on this thread:

Rpmathis - the warpage is the major cause of your symptom.

Throttle body wear mentioned by Fred T - I am sure Fred knows when to install the bushings, but for others the design specification was a clearance of 0.004 ~ 0.006 inch (4 thousands to 6 thousands) as measured by a dial indicator from the throttle shaft to the throttle body in a direction perpendicular to the shaft. In practice, the "break-point" is 0.009 inch. If the wear is 0.009 or less, leave it alone. 0.010 or greater, install bushings.

Jon.

One thing I have not seen mentioned on this thread...

Perhaps it is no longer an issue, it's been 20 years since I learned this the hard way. The older rebuild kits had a brass float that looked like a tiny gas tank. The newer kits have a foam float that looks like a chunk of plastic. The foam is covered by some sealant material. If you adjust the float by pushing on the float itself to bend the arm you will crack the coating where the float is bonded to the arm. The gas (especially gasahol) can attack the foam, and in a few weeks, when it is dumping raw gas down the venturis you will disassemble it and see that your float has shriveled into something resembling a large raisin.

I learned the hard way to always make any necessary bends in the float arm using two pairs of needlenose pliers on the arm, and do not touch the float.

I do not recall the model of the carb I did this on, but it was on my '67 Jeep with a 225 V6. I also rebuilt the Carter AFB on my '69 Javelin about that time.

It's been probably ten years since I have had to rebuild a carb, but I am planning on doing the Qjet on my panel this winter.

Experts, is there still an issue with gas attacking the float if you damage the coating of the float?

thanks for the info, I'll let ya'll know how it goes...

BradB - the term is "specialist" not "expert". From 7th grade math the "x" is an unknown quantity. From 3rd grade English a "spurt" is a drip under pressure. Therefore an "expert" is an unknown drip under pressure.

However, to your question: ALWAYS replace the foam float whenever you disassemble the carburetor. Ethanol WILL attack the float, whether the finish is damaged or not.
:mad:

If you live in an area where ethanol is prevalent, try to find a brass float. If a brass float is not available: before installing a new foam float, seal over the existing finish with a thin coat of POR-15. This cannot be applied to a float which has been in contact with gasoline.

To minimize damage to the finish of the float, DON'T BEND IT FOR ADJUSTMENT! Another method of adjusting the float is to change the thickness of the gasket under the fuel valve seat. Try it.

If you buy original equipment floats, or floats manufactured to original equipment specs (rather than one size fits all), no adjustment should be necessary.

Jon.

I don't suppose that anyone knows if the Carter YF was used in the 1980 F100 straight 6 applications? cause I happen to have one of those at home... how could I ID the YF carb, and would the jets be the right size for the 216 if it came out of the 300 ci ford?

-MIke R.

Mike - Carter made hundreds of different YF carbs. Don't try to use a smog emission carb on your 216. I posted on this forum a few months ago the YF's which are applicable to the Chevrolet. Do a search on topics posted by carbking and Carter YF to find this topic.

Jon.

Ok, found it...

so the answer is no, the YF from my Ford is too big and will flood the little 216 in my '44. darn.. that was almost a free carb for my 216. hmm... so the question is now back around... to rebuild or not to rebuild, that is the question... whether it be nobler to use the Rochester or replace with an appropriate sized carter...

-Mike R.

Jon - Again, thanks for all the good info. While I didn't know the numbers for throttle shaft wear, I do have a good feel for it. It will be nice to know how to measure it.

I have a q-jet body that I junked because I could put a round toothpick in with the accelerator pump shaft and a flat toothpick in with the throttle shaft!

Have to admit I've been cheating on the warpage issue. A friend has a box of B bodies. When we need to rebuild one we sit and match until we find a top and bottom that work together.

Guess I'm going to have to go carb shopping one of these days. My 15 year old will be 17 soon, and refuses to pour the gas now that he's found girls!

Fred - put the boy on one running board and the girl on the other. Then you would effectively have a two-barrel.

Jon.

Hey Carbking,

Just in case no one ever tells ya, your posts are always great. I read them from end to end and am always amazed at the amount of info and work you put into them. It helps out all of us that don't know squat about carbs.

Thanks for the info on here.

46 in progress - thank you, and you are welcome.

Jon.

Hey Jon,
I'll defer to the man who makes carbs work for a living. Noted your "everything else" in good order. When that's the case you are right but we are talking 50 year old carbs here. Just my experience in having chosen to drive one of these beast, many times on 1,000 mile round trips and knowing that I, and that carb, have to bring me back to where I started from.
Always enjoy your posts.