67' Deville back to original fuel pump

[FPM]

Hi!

Working on a 67' Deville. Had an electric pump, which caused trouble, nom going back to original with a mechanical fuel pump.

Working fine, but wondering if there is a return path from carburetor ( COudln't find) in case of excess pressure.

Asking since I found two pipes coming from fuel tank.


Any thought or diagram wellcome!!

[klinebau]

There is only one line from pump to carburetor.  Cars with AC have a return line from pump to tank.

[TJ Hopland]

I would agree, if the car originally had AC then there would be a 3rd port on the pump for the return line. 

What year did they start doing the charcoal canister for the tanks?   That would add a 3rd line to the tank on a AC car. 

[Daryl Chesterman]

According to Caddy Daddy, on 1967 Deville A/C equipped cars, the return line came off of the top of the fuel filter housing, as illustrated below.

https://www.caddydaddy.com/shop-parts/1958-1959-1960-1961-1962-1963-1964-1965-1966-1967-cadillac-with-air-conditioning-glass-bowl-fuel-filter-assembly-used-free-shipping-in-the-usa.html

Daryl Chesterman

[MikeLawson]

Inline Tube sells a set of fuel lines for the engine, the supply line goes from the fuel pump to the fuel filter housing and the return line goes from the top of the filter housing down along side the engine where a rubber hose connects it to the tank return line. If your tank return line is missing, that is also available from Inline Tube. You may also have to do some searching for the correct original glass-bowl fuel filter and mounting bracket.

https://www.inlinetube.com/pages/product-list?year=2030740453787183228&make=3735070329799088786&model=5457996286564957516#?f=6646315064106597807|

[jims427400]

This picture kind of shows the 2 lines in and out of the fuel filter. It is an AC car.

[TJ Hopland]

Interesting,  I didn't know they still used that style filter in 67.   Lots of changes going on in this period.   

[fishnjim]

If not original owner, anything is possible after so many years/owners.   Need to check the build record as to how it was configured.   Can get one from GM Heritage Center. com, if not in the car.
There should be a diagram or description in the '67 shop manual.   Suggest you find one, if not on-line.
Electrics often have too high flow and/or pressure for mechanical systems,(usually used on fuel injection which requires higher pressure and feeds a fuel rail) so they have what in essence is a by-pass for the XS flow/pressure.   They need a lot of controls for a safe conversion.   
My understanding for the early A/C cars return line was more of a safe guard and prevention for vapor lock.   Lots of xtra under hood heat from the A/C system.  10-15% of the motor is running the A/C plus the heat rejected from inside to the high side exchanger with fuel bowl on top of the motor, some came with exhaust in the intake manifold.   (Not real sharp engineering but period correct.)
A proper mechanical won't defeat the needle valve on the float. 

[MikeLawson]

Here are some more pictures showing the correct fuel filter, fuel pump and the connecting lines.

[Daryl Chesterman]

The fuel filter assembly that I linked to from Caddy Daddy would not fit the 67, as it does not have the threaded mounting bracket hole in the top. That must be an error in their listing.   These listed on Ebay do have the threaded mounting bracket hole on the top.

https://www.ebay.com/itm/RESTORED-64-Cadillac-429-FUEL-FILTER-GLASS-BOWL-3-PORT-A-C-NEW-FILTER-SEAL/283775183378?hash=item421251aa12%3Ag%3Aj5cAAOSw04pePbi2&fits=Year%3A1967%7CModel%3ADeVille%7CMake%3ACadillac

https://www.ebay.com/itm/64-65-66-67-Cadillac-Deville-Eldorado-429-Fuel-Filter-Glass-Bowl-Assembly-w-A-C/223787302659?fits=Year%3A1967%7CModel%3ADeVille%7CMake%3ACadillac&hash=item341ac33f03:g:KIkAAOSwHP1d7cZQ

Daryl Chesterman