Mech Fuel Pump Arms

[Ernest]

For SBC,.. whats the difference?

I recently bought a Carter M6900 so i can have a steady 6psi of fuel pressure w/o the use of a regulator.

The original pump that was on my ZZ4 engine and the delphi unit i replaced it with, have the same pump arm shape versus the carter unit i just bought.

Using the edelbrock fuel pumps as an example of what im talking about, 1st pic, my carter m6900, the 2st pic(#1721) and the 3nd pic(#1722), according to edelbrock, the 1721 is for SBC and the 1722 is for BBC, the carter has the 1721 arm and the delphi and the pump prior to that has the 1722 arm.

Why im asking is because, with the engine set to cylinder #1/TDC, the cam eccentric for the mech fuel pump should be on its heel, when i installed the delphi pump some time ago, i remember the pump arm was pushing against the pump rod slightly and i had to put some pressure on the pump itself just to get the bolts lined up on the block to bolt them down, now when i put the carter m6900 pump on, it bolted right in with just about zero resistance, so i dont know if the pump push rod is even touching the cam eccentric. and that bothers me, but i see the reason why now, the pump arms are different. I put the carter pump in earlier today while also revamping the pump to carb fuel line and filter route, but i havent started the engine yet because of this conundrum.

Can anyone shed any light on this, is there really SBC and BBC pump arm only differences?

Thanks

EDIT - This is one fine example why i'd rather convert to an EFI gas tank, route supply, return and vent lines along with a FP regulator and do away with the whole mechanical fuel pump debacle till i can totally commit to EFI.

 

[Ernest]

Happy to report... everything is A-OK, i've used this same pump back in the mid 90s with my '75 chevelle 355cid build, it worked great then, and it works great now, no odd noises or anything, everything sounds normal as it did before, so all that worrying over the fuel pump lever and pump rod was for not.

The fuel pressure bumps between 6.5 and 7.0 psi only, no more, no less, gauge drops back to 0 with engine off, i was hoping for a liitle less pressure, like 5.5 to 6.0, but its much better than it was, and this was just a test run in the driveway, to test for leaks, but i'll be taking the mali out for a drive soon, lastly, i tossed that prior pump, Delphi AMF0001, specs rated for 5psi, it was way off, anyways, right into the trash can, i'll just keep the original one off the motor as a spare.

 

[mikester]

Do yourself a huge favor and get rid of that glass fuel filter. Thats a fire waiting to happen. My buddy had one in his 79 Camaro. I kept telling him to get rid of it. He insisted it was safe. One day he called me at home. He was driving home from work. The glass cracked and his whole engine compartment got gas washed. He was stuck on the side of the road. He didnt realize that the glass cracked when he was leaving work until smoke started coming out from under the hood. Didnt ignite but there was a heck of a mess. Now hes got an AN filter.

 

[Ernest]

Thanks for the advisement on the see through fuel filter... figure the only complaint i see wouldnt be from the glass itself, unless one cranked down too hard inadvertainly cracking the glass, but from the seals, ethanol in todays fuels can wreck havok on them, not like fuel in the past w/o ethanol.

Funny thing is.... i bought the very same back in the mid 90s for my '75 chevelle 355cid build, it was used for 16yrs straight before i sold the car, not one single issue, but i tell ya, the see through type are mighty convinient, at least you can see if the mech pump is pushing fuel or not, but then again,the fuel pressure gauge will tell me the same thing, pressure wise.