1968 L79 Fuel Pump Question

[Michael F.]

Thinking I had a leaking pump housing, I removed the fuel pump from my unrestored '68 L79, with 52K miles. Turns out it was a false alarm and just a bad hose. So, I took the opportunity to clean everything up and take some photos. But the number stamped on the housing isn't what I expected... Is this the original pump for a '68 L79 with a May build date? There's a 68 date stamp in one of the round circles (zoom in the first pic in the circle below the "C"). But the number on the flange doesn't match any of the part number I've seen on this forum. The first two digits of the stamped number are not clear but looks like 0140524. Any ideas?

Judging by the condition of everything around the pump, the gasket, the screws, it doesn't look like this was ever touched so I appears to be original.

Thanks,
--Mike

[Joe L.]

Re: 1968 L79 Fuel Pump Question

Mike------

The generally accepted fuel pump for 1968 Corvettes is an AC type 40658. This pump appears to be a type 40524. AC type 40524 was used on most 1968 Chevrolet passenger cars with 327 engine. I suppose it's possible it was used alternately for Corvettes but I have nothing to support that except for the fact that its configuration appears the same to me as the 40658.

In SERVICE, the type 40524 was known as GM #6416886. GM #6416886 was discontinued over 45 years ago and replaced by GM #6470422 also known as AC type 40725. The external configuration of the 40725 appears to me to be virtually identical to the 40524.

Neither the 40524 or 40725 was ever cataloged by GM for any Corvette application. But, somewhere along the way, someone may have inferred it could be used for a Corvette application.

Your fuel pump bolts appear to be originals.

[Michael F.]

Re: 1968 L79 Fuel Pump Question

Thanks Joe. Looking a little further, according to a post I found in the archive forum, those first two digits are a date code, the first one being probably a C or G which is March or July, and the second probably being an I, which is 1969. So definitely not correct for my 1968 V05O9HT engine. Thanks for steering me in the right direction!

I'm in touch with 3 of the 5 previous owners. I'll ask them if they remember anything about this.

[Joe L.]

Re: 1968 L79 Fuel Pump Question

Thanks Joe. Looking a little further, according to a post I found in the archive forum, those first two digits are a date code, the first one being probably a C or G which is March or July, and the second probably being an I, which is 1969. So definitely not correct for my 1968 V05O9HT engine. Thanks for steering me in the right direction!

I'm in touch with 3 of the 5 previous owners. I'll ask them if they remember anything about this.

Mike------

If you wish to replace this pump, which has apparently worked quite well for many years, with a new pump like it, the "direct descendant" AC 40725 is still available from GM or Delco dealers. One way or another, I definitely recommend that you replace the pump. Fuel pumps are a SAFETY-RELATED component and one as old as the one you have is a "ticking time bomb". In a Corvette, when the diaphragm fails, all of the fuel will siphon out of the tank.

[Duke W.]

Re: 1968 L79 Fuel Pump Question

I second Joe's recommendation. It would be a very good idea to replace that nearly 50-year old pump now. It's a failure waiting to happen. And given that the hose started leaking the elastomers inside the pump are not far behind.

About 1.5 years ago I accompanied a Socal chapter member to the Tuscon Regional to PV his low mileage unrestored '65 FI Coupe. He had gone through the procedure multiple times and had it nailed.

When it came time to start the engine for the PV a geyser of fuel popped up from the RH corner of the engine during cranking. Yep, the main diaphragm ruptured. We had tools, found a pump and jack, but just couldn't get the job done in time, and the '65 Team Leader was very generous with the clock. The pump appeared to be the plant-installed original.

At least it didn't fail out on the road during the test. (We brought it over on a trailer.)

Since the '65 fuel pump has the two piece housing, it's easy to rebuild, and rebuild kits are readily available that have all the elastomeric parts. The all-metal check valves are usually okay, but the elastomers ultimately fail due to repeated mechanical stress and heat over the years.

Duke

[Michael F.]

Re: 1968 L79 Fuel Pump Question

Thanks for the wise words. I ordered a new pump today. There's no sense taking a chance with this old pump. California gas is not kind to old rubber.