I'm bending up some tubing for the engine compartment area (from the tunnel on). So I've got the larger/feed 3/8" OD line done and am now realizing that the fuel rails both measure the smaller 8mm size (or 5/16").

What did the factory do about this connection? What's done with the aftermarket (tangerine, etc) stainless kits? thanks.

ps - the regulator out fitting measures 8mm, so that actually makes since for the return line.

The factory ditched the different sized lines when they switched to the front mounted pump.

This car's a '72.. but it's got the tangerine SS lines, which is a large and a smaller. What's intended for the hook up to the rail? ..Or maybe the later cars had a 10mm rail inlet ?


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If I'm reading this right, you have 3/8 hard line to plumb to the 8mm fuel rail? Maybe there's a reducer fitting that would fit up to the rubber
hose?

Yes you are understanding the issue...

Weren't the factory nylon hard lines in the engine compartment 8mm and 10mm (or something like that), or were they both the smaller diameter? IF they were two sizes, then what did the factory do there in the engine compartment to attach to the rail which IS 8mm ?

Also - Tangerine's SS kit provides two sizes for the short pieces at the engine compartment, correct me if I'm wrong. And it doesn't come with a reducer (tho I know they are available - I have one at the front pump area). So again, what's being done at the fuel rail hook up?

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When I got my tangerine kit I'm pretty sure they had you spec the year and some of the photos showed a reducer for just that reason I think. Check with Chris.

-Edit- description says order the 5pc kit if you want the reducer, https://tangerineracing.com/shop/ols/produc...STL-FL-LN-4-PC3

They do sell it separately.
https://tangerineracing.com/shop/ols/produc...F-UEL-ADP-STR-S

OK that's interesting.. so, two more freakin' hose clamps to deal with. Thanks for the info.

Alternative to the reducing adapter, I've heard of people adding a filter (I'd obviously need 10mm in / 8mm out) just before the injectors (tho I already have one for the FP in the front), so I may do that instead.

Still I'm curious what was done on the earlier cars to make this connection at the rail

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pre 75 the fuel pump is under the engine bay.
the larger diam line gravity feeds the pump from the tank (ie pumps don't really do suction they do push so they need a larger bore feed line). from the pump the pressure line to the fuel rail and return are same size. its the pump that did the reduction.

after 75 not sure exactly how it went in terms of diams but with the pump in the front i am guessing the whole line from pump to fuel rail was same size bore. but i have never seen a 75+ up close and personal to know.

so with a ss tunnel line kit with the two different bores its really replicating factory set up for fuel pump under engine bay? but someone or plenty of someones out there must have dealt with this as lots of pre 75s have had the fuel pumps shfted to front and retained the original tunnel lines (which are pretty much what the SS kits replicate).
some kind of reducer fitting?

using a filter to do the reducing as suggested by @Literati914 is a good one.
if you find the right size inlet outlet.
don't forget to make it a high pressure filter.
you didn't really need a high pressure fuel filter after the pump with the old roller cell pumps. they would never shit themselves into the high pressure line to the injectors.
but modern turbine pumps are perfectly capable os shitting themselves and it could end up clogging injectors etc. so a high pressure fiiter after the pump is worth doing.

i had to replace my original roller cell pump with a modern turbine pump and i have fitted a high pressure filter in the engine bay. its in-line on the hose section after the metal fuel line risers i used to replace the original plastics and before the fuel rail. i fitted it to the decal valve bracket. but i am pretty sure is same diam in and out.

Late cars only use larger diameter line between the filter and the pump (12mm). Everything else, including both tunnel lines, is the same diameter (7mm).

OK, so the answer is: on pre-75 models those shorter lines in the engine bay were the same size, a small diameter. That's what I was confused on. Thanks.

There must be a reason Tangerine's kit are two different diameters up top but I can not wrap my brain around that seems a couple of small diameter lines would be obvious and easy. Then again you'd still need a reducer I guess. Anyway I think some of the D-jet square filters have a big side and a small side ... but is it in the correct flow direction is the question

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i'll take a close look at mine tomorrow. its a 74.
i replaced the plastic lines. but i have all the original fuel lines still.
i see what you are saying tangerine had different diams up top.
that is the short line that come up from below.
i could swear they are the same size each supply to and return from fuel loop to injectors. i'll have a look at car tomorrow.
but my memory is its the tunnel lines that are different, not the engine bay lines after the fuel pump.

mine is an L jet. and.........maybe the d jets were different.

EDIT
just checked mine. both engine bay tube risers are the same.
didn't measure and can't remember but its around 7 or 8mm.
i duplicated the plastic lines.

Stock engine comp lines are both 8mm od. That's standard in my kits too. I offer a 9.5mm engine comp line for those who feel the need.
The factory adapted the diameter from 9.5 to 8 at the filter inlet by using a short reducing hose.

Good explanation and diagrams here :

http://www.914world.com/bbs2/index.php?showtopic=192867

Thanks for checking in Chris and providing a definitive answer on the engine compartment lines.

With an original three port pump (mine's now beside the steering rack).. the large dia. line runs to the pump and has to make it's first reduction going to the pump... then comes out of the pump and has to make it's second dia. change (this time an increase back to 10mm at the front of the tunnel)... then after the rear firewall at some point it makes it's third dia. change, a reduction to 8mm. Now, maybe the later cars didn't use a three port pump w/ all 8mm fittings, I don't know - but these facts are probably a good reason not to use one if moving your pump to the front (an issue I've never heard mentioned), but that's a lot of size changes. Is it necessary to have 10mm at all. I actually considered having both the tubes at the bottom of the tank be the 8mm size instead of large and small - to simplify things.

I'm sure there's a good reason for the 10mm line (which doesn't even run to the rails, but for giggles - what is it?

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When I make up a kit, I change the components depending on which pump and whether in original position or relocated. Changing diameter more than once is a pia so my kits are designed to minimize that. A front mounted pump should have the 8mm supply and 8mm return lines in the tunnel for that reason.
1975-76 model year cars had a front mounted two port pump. All lines except a short hose between the filter and pump are 8mm.

From the PET diagram, It look like the supply line from the tank to the filter is 8mm. Then the filter is 8mm in and 10mm out. 10mm line from the filter to the pump. Pump output is 8 mm all the way to the back.

Filter reduces the gravity pressure from the tank (less pressure out of the filter) so maybe that is why there is a 10mm line between the filter outlet and the pump?

Click to view attachment


If the pump is moved to the front and you want to avoid the number of adapters adding junctions/clamps, the best way is to duplicate the 75 setup and replace the tunnel 10mm for an 8mm. Not sure how easy/difficult it is to find 8mm in/10mm out filters today. Maybe easier to find 10/10 and therefore keeping the 10mm line from the tank to the filter...

Hose between filter and pump on late model fuel system is 12mm

I said that 10 posts ago.

Ah, interesting.. I "inherited" your tunnel lines (in large and small dia.) and made an assumption (ut oh ) that this was correct for all years. I'm gonna reduce with a couple of filters but i don't like the idea of having one in the engine compartment - so, I may replace the 10mm line I bent up the other day with an 8mm - @ChrisFoley would you sell me just that one short piece for the engine compartment (or anyone else have one not being used)?


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My engine comp lines are available individually on my website. I know because someone ordered two last week.