I replaced my Rochester 4 barrel carburetor on my 56 Super 88 with a remanufactured one. With my old one I was getting 17 mpg. With the new one, I am only getting 7 mpg. Can anybody tell me what is happening? It is the same model carb, just remanufactured.

 

Did you do anything else to the engine settings? Perhaps it's jetted differently.

 

"Remanufactured" is a broad term.

You have no idea what's inside that thing.

That's why it's always better to rebuild the carb you have, if it's original.
You did keep the original one, right?

- Eric

 

I took the old one off. I put the new one on. Nothing else.

 

If you have no vacuum leaks and everything is as it should be, then as Eric stated, reman, is a broad term. It's probably jetted differently.

 

Rebuild the old one.

This guy has a good description of how to do it.

- Eric

 

Wow, that's quite a drop in MPG. I would lean towards jet's being incorrect too. Is your choke fully open after warm up?

 

Not a fan of the "rebuilt carbs" you never know it's condition and whats in them, if possible i like to stick with the original and rebuild it because i know what i have. You said you were getting 17 mpg it must have been working fairly well,why did you change it?

 

I guess I screwed up. Carburetor exchange. No I do not have the old. I was having a few issues with the old one. I had to ease into every start at stops or it would stall. I thought I would just start fresh. So, now with that, can anything be done to get my mileage back?

 

You need to fully disassemble the carb and see what's inside, then try to find someone who's good with 4GCs (good luck). If you're lucky you may find something simple wrong in there (like a power valve missing or stuck open).
Also, if your mileage dropped by that much, you could certainly argue that you got a defective carb (because you did), and return it.

I'd keep my eye open for another original from a car like yours, to rebuild. May take a while.

- Eric

 

^^^^
Like Eric said.
If you still have the receipt, I'd be taking it back and ask them to tell you what's going on. At least they can check to see its put together correctly. You got a warranty with it right, 3 months, 6?

 

I am still working on the mpg issue. I had a gas leak on the carb at the fuel inlet based on the threads being stripped. I fixed the leak now, just have to drive it enough to check for MPG's

 

I once bought a remanned rochester carb for my 1955 S88. Inside was clean, everything looked good except both the primary and secondary jets were waaaay oversized...like my carb calls for 49's on both primary and secondary but this carb had 56's in front and 64's in back...way rich and **** poor mpg's. I ended up tuning it to 51 up front and 55 in back. Not the best mileage but a better kick and head snap on acceleration.
Make sure your jets are correct for your vehicle and adjust your accelerator pump and floats for good measure.

 

I took my car to a mechanic (strictly a classic car mech) to have the carb checked out. He thinks the same. When I get it back I will post his findings.