Holley EFI Fuel Tank Module (Holly 12-305)

[kevinshi]

Has anyone attempted an install of the Holly EFI Fuel Tank Module (Holly 12-305) into a 1964 or 1965 coupe/sedan/vert (not wagon)?

Holly stipulates that that unit "Fits 1964-1970 Mustang - 1960-1965 Falcon - 1967-1970 Cougar."

I know enough to be afraid... the fuel tanks/senders on the 1964/5 Comet vs. Falcon confuses the begeebers out of me. I am still not entirely clear whether both had a 20 gallon tank...I know the Comet does and the Falcon MPC says it was 20... but Google has plenty of evidence the Falcon was a 16.

In any case they had a different tank part numbers (C4GY-9002-A vs. C4DZ-9002-A) and different sender part numbers (C4GY-9275-A vs. C4DZ-9275-A). Melvin's Falcon Sender description even warns "FOR FALCON ONLY - NOT FOR COMET."

Anyone understand the difference (and care to speculate on whether the difference is material to that Holley in-tank fuel pump module)? I would really like to use that fuel pump - it will make installing an EFI a ton easier. I worry the sender difference is electrical - that the amount of resistance sent to the comet vs. falcon in-dash gauges is different (and I am using a stock gas gauge...).

My current guess is that the Falcon was indeed a 16. Different tank geometry led to a different sender geometry. Meanwhile that fuel pump has on its list of compatibility the 20 gal tank on the 1969 Mustang/Cougar... and the sender on that '69 tank appears to be super close (identical) in geometry to the '65 Comet's (based on Google images). The fuel pump kit includes three different (swappable)arms with floats, each corresponding to 19, 20 and 22 gallon tank sizes used on various Falcon, Stang and Cougar tanks.

If the differences between the original units is limited to arm float geometry then I think I stand a pretty good shot at getting the file pump to work. I think the '69 float arm is very similar and I would just bend it to match my OE sender (yes I still have mine though it is inoperable).

However if there are other salient differences then the pump may not work. In particular the stock Comet guage would not read correctly if these senders used different electrical logic (i.e. if the amount of resistance is different relative to the coorisponding in-dash guage).

I guess I can call Melvins' in the morning - if Melvin is still around I bet he knows the difference of the top of his head... he knows more about my car than I ever will...

[Baileysvillager]

I ran into this problem when I installed the Holley EFI in my 64 Comet wagon. I opted to go with the Holley external pump and it has worked great. No regrets.

[kevinshi]

OK more information... I can't get Melvin's to answer their phone to I called Jeff @ Falcon Parts. I had just ordered a column shifter detent from them so I didn't feel so bad asking for some free advice...

Jeff confirmed that (excluding wagons) the 64 Falcon exclusively had a 14 gallon tank, the 65 Falcon exclusively had a 16 gallon tank... and of course the 64/65 Comet had a 20 gallon tank. Further the sender to gauge electronics (the amount of resistance) is identical. The salient difference between the senders is the geometry of the float arm.

I then asserted that the geometry on the '69 Stang sender is probably quite similar to the 65 Comet (as they were both 20 gallon tanks). Jeff agreed - said it may very well be that those two are similar. So at the moment it seems like I have a reasonable shot getting the Holley '69 Stang float arm to work in my 65 Comet tank (or at worst bend it a bit to match my OE sender).

Also the two tanks look very similar (1965 Comet vs. 1969 Mustang). On the surface it appears the only difference is where the filler hole was placed (offset for the Comet, centered for the Mustang). I am beginning to wonder whether the 1969 Mustang fuel sender is a reasonable backup option for use on the 1965 Comet (as the later is somewhat difficult to find - see this thread about the fuel sender from a while back).

I will report back in a few weeks as to whether I was successful with the Holley fuel pump...

[SASSY]

"Further the sender to gauge electronics (the amount of resistance) is identical. The salient difference between the senders is the geometry of the float arm."
huh????
Im gonna bend da arm
Lol

[kevinshi]

huh????
Im gonna bend da arm
Lol

That's pretty much where I always end up. A hammer can fix anything.