Not Exactly a "Replacement" Mechanical Fuel Pump - Olds 307

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bob_t442

Not-quite-so-new-guy
Aug 2, 2011
32
26
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southwest florida
In the year of the coronavirus, I've been doing variouss mechanical and cosmetic upgrades to my '85 307HO-powered 4-4-2. Along with replacing the timing chain and gears, water pump and hoses, I also decided I wasn't comfortable reinstalling the 35-year-old fuel pump, so I obtained a replacement from RockAuto.com manufactured by Delphi. Thinking this manufacturer being loosely connected with General Motors previously, I should have confidence in using their product.

Silly me.

While attempting to install this new fuel pump after doing the chain and gears, I came to find out the pump WOULD NOT seal against the block casting without an adapter plate. The meat on the block allowed only about 3/8” all around the fuel pump arm hole for sealing purposes. The new pump has an entirely different casting from the original design. The original had the mating flange immediately around the pump arm, with the pivot pin pressed through the side of the casting through the meat of the mounting flange, through the arm, and back out the other side of the casting. The new pump's casting has a wider mating flange to allow the arm and pivot pin to be installed into the casting together through the mating flange, then pinching the pivot pin in place inside the casting's mating flange hole. The pivot pin appears to be the same length as the original, having roughly 1/4” of pin on each side of the pump arm. This makes the width of the mating flange about 1/2” wider than the original pump flange. This pump design change probably saves 2-cents in manufacturing costs.

To compensate for the difference I made an adapter plate out of 1/8” thick aluminum with external dimensions to match the new fuel pump, and the hole dimensions to match the original fuel pump's mating flange. The pump was installed with a gasket between the block and the adapter, then the adapter plate, then another gasket, followed by the pump. Actually before installing the pump, I had to shave down a non-conforming rib at the bottom of the casting which interfered with the installation of the lower bolt into the block. After snugging up the pump to the block, the fuel line between the pump and the Q-jet carburetor needed to be massaged a bit to make the line mate up to the fitting on the pump.

Working on old cars - always an adventure!
 

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Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
3,831
2,568
113
Galaxy far far away
Do you know how much pressure that Delphi pump is putting out or any rich fuel mixture issues? I just replaced the fuel pump on my 305 SBC and while it bolted on and sealed fine, its putting out 9 psi just cranking the starter.
 

jiho

Royal Smart Person
Jul 26, 2013
1,001
508
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Thinking this manufacturer being loosely connected with General Motors previously, I should have confidence in using their product.

[ .... ]

This pump design change probably saves 2-cents in manufacturing costs.

Well there you have it. That's the connection you can have confidence in. :mrgreen:

But talk about being cheap. At GM pennies here and there can make the difference between profit and loss. For you, another pump is how many bucks?
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
8,090
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For reference, 1985 VIN 9 originally takes ACDelco pump, GM p/n 6472172. Delco p/n 42218. It's a "special" pump with fuel return line. Only used on 84-90 VIN 9 307 best I can find. It's not even in the parts books for 83 and 84 VIN 9, though. The Bulletin announcing the 84 H/O has a parts list that shows the 2172 pump, however. 1983 used a VIN Y pump 1743 (see below) best I can tell, but I'm sure a 6472172 would work just fine. The parts books from that era get a bit wonky in that regard.

Don't know what's so special about the VIN 9 pump.

Another reference, the VIN Y pump is GM p/n 6471743, ACDelco number 41567. I can't forsee this pump being so weak as to not keep up fueal demand from a behemoth 307 VIN 9. :)

There is also some aftermarket pumps that claim to have ethanol friendly construction, but I have no idea about those pumps. If they were any good, that would be a plus.
 
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pizza442

Not-quite-so-new-guy
Sep 9, 2017
23
17
3
I just bought the same Delphi pump MF0006? Trying to get a grasp on what you encountered; are you saying the new pump won't mount flush to the block without the extension you made?
 
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