Old style (62l) fuel tank to replace newer (85l) fuel tank

[ALEX P]

I picked up a new/old tank this week that was for sale locally but it is from an early race car so I need to try to make the fittings work for my 1985 fittings.

3.2 tank (pic nicked from another thread)



Here is what I think may be the way to route the lines on the new tank. Does anyone know why there are two blanking plugs/drains on the older tanks? Would I be better off putting the return through the top or through the second blanking plug at the bottom?



I don't really know much about the fittings on the older tank so was hoping to get some advice. Here's a few pics of the new tank:

[ALEX P]

Can nobody help with the fitting locations on the older style tanks?

[TRE Cup]

you are on the right track about using the bottom right bung for a return.
What you may not know is that 74-89 tanks have a "swirl pot" in the tank for the supply to the pump. This design is so there is always gas available , till its very low, for the pump to suck on.
Early design tanks do not have this and what happens is that when you get into a fairly sized curve (going left more so than right) the pick up is exposed in the early tank. No gas. You can hear the pump get louder and higher pitched when this happens. This will shorten the life of the pump dramatically if this happens a lot.
You will adjust to what level works for your car after hearing the pump whine a few times and noting the conditions/ fuel level
Other than that , looks like a neatly done extra capacity tank. Make sure there is no rust as that will play havoc with your cis parts

[ALEX P]

Thanks for that, I did know about the swirl pot as it prevents you from applying any protective coating to the inside of 3.2 tanks right?





I've managed to get a light inside the tank and did see a little bit of light rust in there, I also see that there is a load of sponge type material, presumably this helps prevent the fuel 'sloshing' around too much.



I was hoping to seal the inside of the tank, maybe with a product like POR15 but I guess the sponge material won't allow this. The car has a later engine so Motronic but obviously I don't want be running contaminated fuel.

POR15 Deluxe Big Fuel Car Tank Repair Sealer Kit | Frost Auto Restoration Techniques

I hope I haven't bought a big lump of scrap. Maybe it will need surgery to put it right as in a panel removed to get proper access to the inside and then welded back in place or am I getting carried away? The tank hasn't been used for a number of years so I guess moisture in the atmosphere has created the internal corrosion.

[TRE Cup]

well.. the fuel cell foam that someone put in there does reduce slosh, but pray that it has not broken down from long term exposure to gasoline. Another concern would be how that old foam reacts with the crap ethanol in present day gas. I would make sure that the fuel filter is replaced after a few tank fulls and cut open to check for debris.
Safest to cut open the tank, remove the foam and get it treated/sealed. You can fabricate some anti slosh plates and install them before welding it back up.

Bottom line is how much do you want to spend, getting the larger capacity and period rally look when you open the hood

[ALEX P]

Cut open the tank you say? Why not!!

I managed to get my hands on a reasonable 3.2 tank so cut that in half too. Plan is to use the bottom half of the 3.2 tank with the top half from the race tank so I get the correct fittings and keep the swirl pot. I may also add the boss from the sender whilst it's all in bits.

The foam that came out wasn't great so I'm glad I never ran it. The corrosion inside the tank was also not as bad as I first thought so it should clean up ok.

Has anyone got a recommendation for a coating product other than the POR product above to use to protect the inside of the tank?

I was thinking of cleaning it all up, coating the inside up to the seam then welding around the seam and carefully pouring some coating/paint into the tank then 'rolling' it around the seam to coat that without getting it near the swirl pot/filter etc. Does that sound a sensible plan?

[ALEX P]

Just thinking - my current fuel pump is a but of a lashup/eyesore so will be replaced when I swap the tanks over with a new Bosch 044 pump.

Is there any reason I can't weld a bracket onto the fuel tank to mount the pump instead of mounting it to the car?

[TRE Cup]

Sure: Two things if you try this
1) welding may very well cause an explosion
2) the tank will not be able to be removed or installed from the car

So... NO . don't do that

[ALEX P]

Originally Posted by TRE Cup

Sure: Two things if you try this
1) welding may very well cause an explosion
2) the tank will not be able to be removed or installed from the car

So... NO . don't do that

Well, it's a little late to not weld the tank as it's currently in two halves!! (see my previous post). Welding a bracket to the bottom half won't make it any more dangerous.

Currently to remove the tank from the car (not a regular occurrence) I have to undo the feed and return pipes so the only real difference would be that I would also have to detach the pump from the tank which would be two bolts or similar.

The current setup is not pretty and I'm not proud of it, it was more of a quick fix from the previous owner who just had a single jubilee clip round the pump to the chassis which broke so I replaced it with two new ones and a bit of rubber behind it.

I'm now looking for a better way of mounting the pump as I may switch to a Bosch 044 pump and the stock setup is quite crude so thought mounting it off the tank could be a viable alternative?

[TRE Cup]

oops- did not read the threads to see that you had cut open your tank. so #1 explosion risk no longer applies.

ok- back on topic; any brackets you weld to the tank will interfere with the opening in the bottom of the car. You have to curve the tank install as it is, to get it to seat properly and expose the entry/exit fittings in the right place. Weld too long a bracket there and it won't go it.
You MIGHT be able to weld a small saddle bracket to the tank next to the fitting holes, but test fit your experiment with hoses, fittings, sample saddle, and the 044 pump. really tight down there

[ALEX P]

Originally Posted by TRE Cup

oops- did not read the threads to see that you had cut open your tank. so #1 explosion risk no longer applies.

ok- back on topic; any brackets you weld to the tank will interfere with the opening in the bottom of the car. You have to curve the tank install as it is, to get it to seat properly and expose the entry/exit fittings in the right place. Weld too long a bracket there and it won't go it.
You MIGHT be able to weld a small saddle bracket to the tank next to the fitting holes, but test fit your experiment with hoses, fittings, sample saddle, and the 044 pump. really tight down there

Hahaha, no worries, I'm not brave enough to weld onto a used fuel tank with old petrol swilling round the bottom

I thought of basically adding a simple bracket to pretty much replicate the current position of the pump just mounting it from the tank instead of from the car.

Good call on the 044 pump being a bit more of a squeeze. I will do a trial fit first - I haven't seen any photos of one fitted so can't gauge how much space there is or isn't!

[TRE Cup]

one last thought before you go ahead with the weld on bracket, for the pump. consider that you are mounting a vibrating pump to a bracket that is welded to the tank. Sooner or later you run the risk of the vibration causing a crack, around the welds, and hence a leak.
Also, me thinks that the pump will hang down and be the lowest part of the car , exposed below the tank. Food for thought when you have the unavoidable obstacle in the middle of the road

D

[ALEX P]

Still undecided on the best way to mount the pump but still have some time to figure it out.

In the mean time I've just been cleaning up the two tank halves.

Fitted them together with the extra rear section removed so that I can paint inside the tank when it is 3/4 welded up but may have messed up as I cut a 'V' in the top of the tank to allow for the baffle in the bottom of the tank where maybe I should have just removed the baffle in the bottom of the tank?

End result is that I have a double wall so after an opinion here - would you cut the top section so that there is half and half, leave as it is with a double wall or remove the bottom baffle.

Does that make any sense?

[ALEX P]

I couldn't resist removing the swirl pot and quite glad I did as it had a fair bit of corrosion around it and it also makes cleaning the fuel lines and all of the nooks and crannies around the swirl pot a lot easier.

The main surface rust came off ok with a wire brush and it will all re-assemble no problem but I was kinda thinking that while it's all apart maybe it would make sense to make a slightly cruder steel replacement without a lid just by rolling a bit of sheet and tacking it to the bottom.

I've been trying to figure out whether it's necessary to have a lid on the swirl pot if the tank is already quite baffled.

[911pcars]

Not sure the objective of welding a bracket to hang a vibrating 2 lb. fuel pump off of it. If firmly attached, the FP will transmit and accentuate pumping noise - louder as the fuel level drops. What's the planned location for the FP bracket?

OTOH, what's wrong with the factory location on the crossmember? It's at the same level as the tank bottom (gravity supplies fuel to pump), conveniently close to tunnel line (shorter hose path) and fairly easy to access.

Sherwood

[ALEX P]

Originally Posted by 911pcars

Not sure the objective of welding a bracket to hang a vibrating 2 lb. fuel pump off of it. If firmly attached, the FP will transmit and accentuate pumping noise - louder as the fuel level drops. What's the planned location for the FP bracket?

OTOH, what's wrong with the factory location on the crossmember? It's at the same level as the tank bottom (gravity supplies fuel to pump), conveniently close to tunnel line (shorter hose path) and fairly easy to access.

Sherwood

It's a fair point Sherwood, empty vessels and all that!

I was just trying to explore as many options as possible while it is possible to weld to the tank but as you say a stiff crossmember is going to be a quieter mounting point than an empty tank.

A couple of posts ago I added a picture of my current lash up so maybe I'll explore better options of attaching to the crossmember than jubilee clips.

[911pcars]

Alex,
While an elegant attachment point to the crossmember is fine (e.g. factory OEM), like you, I merely clamped an aftermarket Airtex FP to the crossmember, making it a rigid mount. I wrapped the pump with some cut sections of radiator hose to help reduce pumping noises through the chassis.

FWIW,
Sherwood

[ALEX P]

I've been a bit lazy on this recently but car is back on the road in a couple of weeks so decided to treat it to a new Bosch 044 pump & keeping the crusty old pump as a spare.

I thought I'd be clever and bought a couple of pump clamps then cut the feet off them and attached them to bobbins bolted to the crossmember. It was a bit of a squeeze but worked out nicely and the fuel pump noise was dramatically reduced when I flicked the switch on a test run.



What I didn't consider was that these would then hit the belly pan so when I put that back on it clashes with the pump brackets and tightening the bolts bows the belly pan. Instead of binning the clamp idea I'm thinking that I may just cut a pair of slots in the belly pan and add some relief in the pump area.





While the tank was out it gave me the opportunity to do a quick trial fit of the two tank halves to make sure the bonnet would close. Bit of a mixed bag here as the bonnet closed fine however the duct from the front cooler just wont clear the front of the tank.



When I was running a full fat Bosch silver battery I had to add a cut out section to the duct so may have to extend this across the whole length of the duct to allow enough clearance.



It's never easy is it!!!

[ALEX P]

I've been off this project for a while as the car is off the road for much needed rust repairs but have booked some time in a couple of weeks to progress the tank.

I really don't want to re-use the swirl pot because when the tank is welded shut again I want to seal the inside with POR15.

I was thinking of simply welding a couple of baffles (possibly with a lid) around the pickup/return area to replicate the swirl pot. Something like in the crude photo below.

Has anyone else done this or knows of a good reason not to do this?

I would obviously add a couple of holes or slots to let the fuel in!!

[ALEX P]

Well if nobody has any objections! We replaced the swirl pot with an open top steel version which should hopefully do the job ok.

The 65l tanks had no baffle and no swirl pot and the 85l tanks had both.

I'm going to seal the inside of the tank with the POR 15 tank sealer or similar product such as the Bill Hirsch product (any recommendations?) so the original swirl pot had to go.










Next job was to cut the sender mount out of the old tank and weld it onto the new tank top because running a fuel tank and guessing the amount in it isn't really practical on anything but a race car.















Last job was to plasma cut the front of the the tank lid so that a flatter plate can be welded on there so I get the clearance needed to clear the scoop.







I want to end up with an under bonnet centre fill tank so I can bin the old filler cap/tube/pipe assembly and keep things simple and the spare wheel part of the tank was completely redundant because of my scoop so hopefully when all done this project will have made some sense.