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!
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!