What is the difference between a 40083 Fuel pump vs. a 4657 pump?

[John R.]

Wondering what is the difference between a 40083 Fuel PUMP Vs.4657 pump? I have a 66 SB and wondering if they both will work?
Was the 4657 made for other cars and the 40083 was dated just for the 64-66 mid year?

[Gary B.]

John,

Joe Lucia has previously given these as the applications for the 4657 fuel pump:

“The AC 4657, aka GM #5621665, fuel pump was used for the following:

L1958-61 passenger car with 348
1959 passenger car with 283 cid and FI
1962-66 passenger, Chevelle with 327
1962 passenger with 409
1963-65 Corvette with 250, 300 hp

It was also SERVICE for 1959-62 Corvettes, but I'm not sure that it was the same pump used in PRODUCTION. It may have been, though.“

Gary

[Gary B.]

John,

Dan Bachrach asked about the difference between the 40083 and 4657 pumps back in 2005, but there isn’t all that much information in that thread.

https://www.forums.ncrs.org/forum/te...ps#post1132344

Gary

[Gary B.]

John,

From what I can see one major difference between the two pumps is the orientation of the inlet and outlet ports. The first attached photo shows the 4657 ports. They are about 90 degrees apart.

By contrast, the ports on the 40083 are 180 degrees apart. The second attached photo shows an early-style 40073 pump with the cast bottom.

Gary

[Gary B.]

John,

Finally, based on multiple photos I can find of the 4657 fuel pump, those pumps appear to lack the two “gussets” at the base of the tower with the AC embossing. In the attached photo of a 40083 pump you can see the gussets at the 8 and 10 o’clock positions. (Later service replacement 40083 pumps lack those gussets and lack the AC embossing.)

Are you trying to find a substitute for the 40083 pump for your ‘66?

Gary

[John R.]

John,

Finally, based on multiple photos I can find of the 4657 fuel pump, those pumps appear to lack the two “gussets” at the base of the tower with the AC embossing. In the attached photo of a 40083 pump you can see the gussets at the 8 and 10 o’clock positions. (Later service replacement 40083 pumps lack those gussets and lack the AC embossing.)

Are you trying to find a substitute for the 40083 pump for your ‘66?

Gary

Great info on the pumps guys!!! Learned a lot.Mine started to spit out gas through the 2 holes on top just today.I assume the diaphragm is shot.I just wanted to make sure I order the correct one.

[Gary B.]

John,

Is someone selling a 40083 equivalent? Airtex used to sell one but I thought they were out of stock for much of the past year.

Gary

[John R.]

John,

Is someone selling a 40083 equivalent? Airtex used to sell one but I thought they were out of stock for much of the past year.

Gary

Well I needed to know which one to order and mine is a 4657 and not a 40083. I search eBay and there are a few on there that are refurbished. I went that route as I did not want to buy a Chinese piece of crap.Few guys had 100% ratings.Hope to get it in a few days.I wanted to make sure the inlet and outlet ports were correct.

[Gary B.]

John,

You’re lucky you need the 4657 fuel pump and not the 40083. The 4657 pumps can be found, with the AC embossed tower and bottom. The 40083 are much harder to find with the right cast features, and therefore a fair bit more expensive.

Like the 40083 pumps, I think the 4657 pumps originally had a similar “tiger stripe” pulsator cover gasket, and for the 40083 those gaskets are close to impossible to find these days. But that’s a pretty minor detail.

Gary