VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Rochester carb question

I have a Rochester carb that has been recently re-built by my mechanic. It has the numbers 7004477 and K1 stamped on the metal tag, as well as 18(?)punched through the tag. When placed on my '53 235 engine it bogs down in the low range and upon acceleration. I was told that this carburetor is too lean for this engine and that I need to bore out the accelerator pump passage and maybe the secondary idle hole by a few thousands.
Does this sound like the right advice?

Thanks,

Kelly

The carb. is correct for a 1953 235 engine.Actually any of the 235 Rochesters will work fine with your engine.

The advice sounds very incorrect...In its original form with no changes this carb. should perform well.

The first item that I would suspect is the accelerator pump plunger.Either the incorrect bowl cover gasket was installed which blocks the gas passage from the pump well to the air horn-The check ball in the bottom of the plunger is missing or stuck, plunger leather or "rubber" seal is bad, or the bowl check valve is missing or?? or the passage is plugged up that carries the gas to the inside of the air horn.

Remove the air cleaner-Use a flashlight for better vision and open the throttle by hand-with or with out the engine running-If pump plunger system is functioning properly a squirt of gas will be visable when throtle is opened.If not there is a problem with one of the areas that I mentioned.I would look for another mechanic :confused:

Yes, Gene is correct as he almostly always is!
As he says any good Rochester one barrel jetted for a 235 can be made to idle, and accelerate without the bogging down, if not a replacement is usually not too far away, there are usually a couple on EBAY Motors. I have bought them for $10 to $20 dollars and a NAPA kit (with a good instruction sheet) is about $15
and a couple cans of B-12 carb cleaner are less than a 10 spot at Walmart.

A question, have you checked the heat rizer flapper valve? probably not a factor now but that needs to be checked.

If your carb has an auto choke is it opening fully after it is warmed up?

Also have you been able to drive the car until it is at normal operating temp?

I would believe that in addition to his advice you may just have a still dirty carb, probably in the fuel passages in the throttle valve body or rust.
I would think about useing another mechanic, even when useing this carb for high performance (Two or Three at a time) I never heard of anyone boreing out the accelerator pump passage itself.

I do some changeing of the main high jet from time to time # 56 to lean from a #57 and a #58 for a one step richer, I have found many 53 model 235 carbs using larger jets like those in the 261 Rochester model "B" carb when the book shows a #65 Main jet(standard) and a #64 (one step lean) and a #66 (one steprich) and others using the smaller jets from a 216.

I usually find dirt & crud in the fuel passages or a leaky vacuum line to the wipers or the vacuumn advance. I haven't ever found another make of carb that is as well suited to the 235 engine as the Rochester model "B".
The model "B" is Standard on the 53 & 54 1/2 ton trucks.

I do not use an model "BC" (auto choke) myself but many do use the "BC" Which requires a little more plumbing to get heat to the choke thermo-control .

Thank you Sir, I've had my doubts about this guy lately.
One point I failed to mention, around town,it runs a bit better if I leave the choke out about half an inch.
Does that change the equation any?

Kelly

Kelly, since you do have a manual choke I do believe Gene's and my advice are what you need, more than likely a mere soaking in the mechanic's carb tank and a cursury blowing out with compressed air left a restriction in the fuel passage or passages.

The choke being out and improving the "running" indicates a lean condition.Could be my first answer, a vacuum leak, the heat riser, or a stuck power piston in the carb.The power piston enriches the mixture and is controlled by manifold vacuum--not to be confused with the pump plunger.

WHAT IS THE CARB # FOR A 54 ROCHESTER 1 BARREL MANUAL CHOKE FOR A 235 ... MY # IS 7004622 BUT CAN`T FIND THIS # ON ANY CHART ORDERED A 7005921 CAME BACK A AUTOMATIC CHOKE .. FOUND ANOTHER # 7004468 BUT DON`T KNOW IF THAT IS RITE .. ANY HELP ?? THANX chance moore

1954 hand choke 235 truck carb. was a 7004468.

Stick shift car had automatic choke..number was 7005921

Power Glide with auto, choke was 7005922

The 7004622 part number was replaced by 7004512 -can't find what it is but I think its just a part of the carb...such as the bowl or???

Do you have a car or a truck??stick or automatic??


The carbs. were all basicly the same..had some minor jet differences and power piston spring tension but all will work OK without modifications.

Important that power piston recieve vacuum.,not be binding,all acc. plunger check balls in correct location, etc. as well as check ball inside plunger.