Fuel Pump Ene(g)ma! (sic)

[Joe C.]

Were their two different pump body castings for 644008 fuel pumps............early and late?
I believe that these were used from 1963-1966, for 340/350/360/365/375 HP engines.
Thanks in advance.

Joe

[William C.]

Re: Fuel Pump Ene(g)ma! (sic)

I believe you are referring to the 40083 pump, used on all the SHP engines 64-66, and the answer is there were only one version of both the top casting and the center section originally used, but there were two versions of the bottom, one stamped and the other one cast. Service replacements are available from some vendors with the same part number, but they have a different top body casting than the originals, both in material (aluminum vs magnesiun) and and configuration as they lack the "wings" molded into the top section of an original. If you do a search of the archives, I posted a picture or two sometime in the last month.

[Joe C.]

Re: Fuel Pump Ene(g)ma! (sic)

I believe you are referring to the 40083 pump, used on all the SHP engines 64-66, and the answer is there were only one version of both the top casting and the center section originally used, but there were two versions of the bottom, one stamped and the other one cast. Service replacements are available from some vendors with the same part number, but they have a different top body casting than the originals, both in material (aluminum vs magnesiun) and and configuration as they lack the "wings" molded into the top section of an original. If you do a search of the archives, I posted a picture or two sometime in the last month.

Bill,

From what I have been able to determine, you are correct about this pump being cast magnesium. This is a VERY rare item, and was only used for the few years on ORIGINAL 40083 pumps, and a very few Cadillac pumps. The vast majority of fuel pumps (as is ALSO true of all Holley and Rochester carburetors) were and are diecast zinc alloy, "affectionately" known as "potmetal". None of these items were ever cast in aluminum, or magnesium (because of its very high cost). In fact, the only carburetors which were cast in aluminum, was the Carter AFB (aluminum four barrel). I see now, that certain high performance series carburetors, such as Holley, are being cast out of aluminum (at additional cost) for a boasted weight savings of 3-4 pounds over diecast zinc alloy.

It was because of the pictures and information which you sent me a few weeks ago, that I was able to find a beautiful, original, and VIRGIN 40083 fuel pump. I purchased it from Gary Seymour, who posts here. I also bought a "real deal" rebuild kit from:

http://www.classicpreservation.com/

I couldn't have done it without your pictures. The 1965 TIM&JG DOES NOT MENTION THE MOST IMPORTANT ASPECTS WHICH MUST BE PRESENT ON A TRUE ORIGINAL PUMP. According to the 1965 TIM&JG, as long as it has the "AC" logo cast into the top surface of the "tower", and "40083" stamped into the mounting flange, then these 2 characteristics indicate originality. There are some very reputable Corvette specialty parts houses, who are selling pumps WITH the AC logo and "40083" stamp, as "original, rebuilt pumps", even though the upper casting is different in at least TWO other respects. THIS IS THE REASON FOR MY QUESTION, as I am now somewhat confused.

The 1965 TIM&JG states that there are 2 acceptable style "pulsator covers". One is cad dichromate plated stamped steel. The other is diecast zinc (potmetal), to match the body and pump cover sections, with "AC" cast into it. COULD THERE HAVE BEEN AN "EARLY" AND "LATE" PUMP CASTING DESIGN TO CORRESPOND TO THE TWO DIFFERENT STYLE PULSATOR COVERS?

Some pictures will help explain.

Here is one of the pictures of an original pump, that you sent me:

Notice some very important characteristics shown here (in addition to the "AC" logo), which are NOT mentioned in the 1965 TIM&JG:
1. Two radial ribs radiating from the base of the "tower" (one cannot be seen here).
2. The double step adjacent to the mounting flange, comprising the boss for the rocker arm pin.
3. The use of a "plain steel" rocker arm pin with an "x" head mark (not seen here), which must be deformed on the opposite end over a small flat washer, generally ALSO in an "X" pattern for retention.

Now, here are 2 photos of the pump which I bought 2 weeks ago:





The pump that I purchased, clearly has all of the earmarks of an original pump. This pump has the stamped steel pulsator cover!

Now, here is the typical pump, selling as a "rebuilt original" from at least 1 vendor. I don't know which pulsator cover these pumps have. Notice the
key characteristics that are missing here.


I realize that the TIM&JG does not and can not always give a full description of each item. But these are important characteristics to add, if, in fact they are pertinent.


Joe

[Alan D.]

Re: Fuel Pump Ene(g)ma! (sic)

Joe,
If you notice on the installed pump a small line exists under the A pointing towards the C. The original pump just purchased does not have this line.
Now my original pump with metal bottom has the line, however my later one, also with flat bottom, does not have line. Just a few more details!

[Joe C.]

Re: Fuel Pump Ene(g)ma! (sic)

Joe,
If you notice on the installed pump a small line exists under the A pointing towards the C. The original pump just purchased does not have this line.
Now my original pump with metal bottom has the line, however my later one, also with flat bottom, does not have line. Just a few more details!

Alan,

You bring up an interesting point! Because the line which you mention is not a typical part of the "AC" logo, I would be more inclined to call it a casting flaw, which further leads to a conclusion that all those pumps with that flaw, are later produced original equipment pumps. Taking that line of reasoning further, leads to the conclusion that the pump which I purchased, with a "clean" logo, and a stamped steel pulsator cover is an early production original equipment pump.

Now, look again at the "rebuilt original" pump offered by the parts houses. Notice that the "AC" font is noticeably smaller on these. These later style pumps also use the diecast pulsator cover. If you'll permit some speculation, then we might hypothesize that those pumps are actually early service replacements. Possibly, if not probably, when the second design pump, used for early service replacement were cast, the flaw disappeared, as well as the adoption of the new design, and the smaller font "AC" logo. The diecast pulsator covers were apparently carried over from the later produced original equipment pumps.

Joe

[Alan D.]

Re: Fuel Pump Ene(g)ma! (sic)

Agree its just a casting flaw. Now my original pump (Mar64 car) has the dash flaw while the other does not.

Inside the mid section of the pump some numbers can be found. My original has the number "64" while the other has "67" while all other numbers are the same.
My second pump was purchased over the counter at an AC Distributor before 1969.

[Joe C.]

Re: Fuel Pump Ene(g)ma! (sic)

Agree its just a casting flaw. Now my original pump (Mar64 car) has the dash flaw while the other does not.

Inside the mid section of the pump some numbers can be found. My original has the number "64" while the other has "67" while all other numbers are the same.
My second pump was purchased over the counter at an AC Distributor before 1969.

Alan,

If you could post any pictures, especially of the OTC pump, that would be helpful.

Joe

[Alan D.]

Re: Fuel Pump Ene(g)ma! (sic)

Believe you want the inside section with the numbers since your pictures are great! So these should be of help.

[Joe C.]

Re: Fuel Pump Ene(g)ma! (sic)

Believe you want the inside section with the numbers since your pictures are great! So these should be of help.

Great pix!
I'll post my innards when I git 'er done.

[Alan D.]

Re: Fuel Pump Ene(g)ma! (sic)

Original pump on right with orange (not original over spray), the other is OTC.
Hope you're keeping all this great info for an article.