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Sat Jan 01, 2022 2:56 pm

So I am having issues with my gas tank. Its a '73 (carbed car) Would it be possible to fit a gas tank from a later, fuel injected bus? I want the return connection at the bottom for the ALH motor that's in it now.

Sat Jan 01, 2022 4:10 pm

It'll fit, and most of the vent lines will be similar. If your bus is an early 73 with the tube style sender the fuel gauge will jump around like a blur with the later sender unless you swap the gauge as well.

Sat Jan 01, 2022 7:04 pm

Thanks for the reply. Do the late bays use the vibrator regulator? I can easily score one of those...what I cannot seem identify / find is a late fuel gauge. All of my searches bring up the earlier ones.

Sat Jan 01, 2022 10:06 pm

arminyack wrote: Thanks for the reply. Do the late bays use the vibrator regulator? I can easily score one of those...what I cannot seem identify / find is a late fuel gauge. All of my searches bring up the earlier ones.

My understanding is that the gauge, regulator and sender all work together as a team. Late units use a gauge that has a heated needle, an electronic or mechanical bimetallic regulator, and the sender. The gauge needle is moved by how warm it gets, which changes the position based on a bimetallic strip. The mechanical regulator turns on and off to keep the gauge heating wire from over heating, and the electronic one drops the voltage to reduce over heating of the gauge. The electronic one is used when the dealer installed electronics that could pick up the mechanical regulator turning on and off.

Sun Jan 02, 2022 9:18 am

Hmmmm....., I see what you mean about only early ones for sale, usually it's the opposite. There is one black faced one mis identified as 62-67, it's NOS and priced to reflect that. Keep searching, or contact sellers parting later buses and ask.
As SGK says the guts of the gauge are different and everything works together. The early gauge will work, but the needle will jump hysterically with every slosh of the tank. It's still better than no gauge at all, when the wiggling stops it's time to get some gas, and it's not something you have to pull the motor to replace if you ever come across the right unit.

After my initial reply I also thought of the upper center vent on 72/73 tanks that the later ones lack, you may have to fill slowly if you can't come up with a way to add a vent there.

Sun Jan 02, 2022 10:34 am

Fuel injected tank, late float type sender and a gauge cluster from a '74 (so it looks sort of proper colour-wise) No clue how much work it will be to make the late cluster work with the wiring of the '73, but there will be work. The early and late clusters are quite different, you can't easily take the guts of one and swap it into the other.

Another solution that might do the trick, if you're handy, is making some kind of adapter plate to allow the tube sender to work in an injected tank. For example gut the float type sender to keep just the top stamping that bayonet-locks to the tank, then machine a ring to suit the tube type sender and make a kind of hybrid early-late tank. Or cut your existing tank (shame to ruin it but...) and braze the part that carries the sender onto an FI tank. Third idea (easiest?) is just to add a nipple onto the existing tank for the return. There are 8mm screw-on nipples available that fit the early tank threaded nipples. A diesel will need these.

FI tank is the best tank to use because of the size of the nipples and the built in anti-splash baffle. Especially for diesel where the return will come into the tank at a very fast rate. The new "FI" tanks lack this baffle by the way.

The more I think about the gyrations needed to make watercooled engine swaps work, the more my head hurts. The downstream effects of changing something or a bunch of somethings can be hard to anticipate.

Sun Jan 02, 2022 11:14 am

It may be best to just Tee the return into the center vent nipple at the top of the tank you have now. So much less plumbing and wiring fiddling required for that.