Fuel Tanks, Fuel Returns For Sniper on a Lump

I have split this off from my generic XJ6 Jaguar fuel tank and returns discussion as it now includes how a Holley Sniper will cope with the smaller return pipe in the tank and and the 6mm feed to the pump even though it’s only about 30cm from tank to pump.

Actually the tanks go to a Pollak 6 port valve first as it will be a single external pump.

The discussion is where it is because the original tanks in my '75 series 2 have blanked off returns (6mm) and it would make life a lot easier if I can avoid removing the tanks to replace with series 3. Plus I’ve hit a brick wall getting the mufflers out :hot_face:.

Am I correct in assuming that with immersed pumps (in fuel injected cars) there is no return? I only ask because instructions for fitting the Sniper say a return is only necessary for external pumps and reg. An immersed pump does not require a return or external regulator.

Plus I was having a squiz at new XJ6 tanks and the ones for immersed pumps have no spigots apart from the vent.

Both my LSx corvette and bmw with in tank pumps have returns. Never seen an injected motor without a return of some sort. Btw… Andrew at jag specialties has done this every way you can imagine and is a great guy to talk to.

They return, just not from the rail. Think it was about 03 it came along in trucks, but the 00 Camaro 350 we have is returnless as well so I’m not sure. There’s a handful of different ways to make it happen when doing swaps.
I kinda prefer a return style tbh.

Okay then, that’s what I thought too then I saw pics of replacement XJ6 tanks for immersed pumps with no spigots so I got curious.

This style is pretty common, long as your pump will do 60psi or so, stick this in and plumb it up.

OE’s have been using PWM and there are some aftermarket solutions to keep fuel pumps from overheating on higher HP apps, lots of neat stuff out there anymore.

That’s what I used on my corvette but it still requires a short return to the tank. I think that was Dons concern, his tank doesn’t have a return fitting.

Which would be ideal but I think the Jag immersed pumps only do 36PSI.

Well, yes and no. I discovered the tanks in my '75 ex-carb car actually has plugged-off returns but are only 6mm. The fuel feed is also only 6mm but may still work okay.

I’ve managed to upgrade the in-tank pumps on a couple of LS swap vehicles with higher pressure units via some creative hanger modification. I don’t know anything about the XJ6 setup off hand but it’s worth a ponder. There is probably a fuel flow needs vs fuel line size calculator online somewhere.

Yes. 3/8th fuel line to the front and 5/16 return. I was hoping to get away with the short 6mm lines from the tanks to the pump and returns because of how low the pump and return spigots are. Of course the long line to the front and back again are bigger.

I ran a warmed SBC 350 off the original (1975 xjc carb car) fuel line with no problems, prob 350hp, ran it hard too. Personally I would stay with an external pump in the trunk with corvette filter regulator, and the stock tanks and plumb it all for the Sniper fi. The existing returns would be easy to plumb, I still don’t think the sizes are going to hurt anything. Andrew at Jag Specialties has the really hard to get odd size fittings.

That’s still 8 something pump PSI against 58PSI for the Sniper. 6mm to the pump may cause starvation issues even though it’s only about 30 cm but we’ll see. 58 PSI is a lot to suck thru 6mm to 10mm. The 6mm return I’m not really worried about.

Understand Don, and I have to agree. Only way to know is to try it, so could be worth the money to get new clean ser 3 tanks now and have it all done. Around 300 ea from rock auto btw… Same Spectra tank as everyone else’s.

An update for those who may be interested. After a consensus of FI experts that the smaller return lines would be fine, I decided to take a chance on the original tanks with the 6mm return. One little win was I discovered the feed line to the carbs was 8mm anyway so I’ll use this for the longest return.

As they were relatively clean and without issues whilst in service with the 350 I took the tanks to a well regarded tank and radiator workshop to get a good dipping and new spigots soldered on.

I went with soldered rather than stuffing around with made up and old threaded fittings as I wanted to install the tanks without having to worry about possible leaks. Just the thought of having to get those flippin’ tanks out again just for maybe one drip made me want to puke.

Should get the tanks back next week.

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Watching your thread Don. Any progress? What location on the tanks did you put the returns? Or did your tanks have the returns just aft of the supply lines? If so I suppose you would have brought them in the car maybe using the same holes as the supply lines?

Apart from occasionally going out to the shed to stare at the monster I’ve created and immediately running back inside sobbing loudly I haven’t done much at all lately.

As previously mentioned, I did take the original tanks out and found I could have used them with the existing blanked off 6mm return and enlarging the feed line but as they were out I thought I may as well start again with new tanks. The issue with that is the return is at the front because the series 3 plumbing is routed between the boot wall and the diff cradle.

In answer to your last question, yes, next thing is to bring the return line rearwards and and across thru where the supply cross-over goes.

I made some progress yesterday. As I’m going to use the original fuel line as a return I began on the opposite side to feed a 3/8 soft fuel line over the cradle and will then make a hard line to the front.

I had big plans of installing a complete series 3 main fuel line but as this would require the removal of the entire suspension assembly I went with the soft fuel line over the cradle.

Now I’ve got over the heeby jeebies and started again I’ll post some pics.

Today I started installing the new RH tank. I should’ve read some more because I discovered the mounting bolt threads are different. Grrr. Out it came and down to the bolt shop tomorrow for some new bolts. Two steps forward and one back.

I think that this could be true for every single one of us on here… :slight_smile:

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Don, the new tanks I got had the same bolt threads? Fine thread standard bolts I think?