3.2 in a 73: Center tunnel fuel line options?

[Shaun @ Tru6]

I'm taking the 3.2 out of the 86 and putting it in the 73. Coming along are the oil system and the fuel system. But I have no desire to pull the center tunnel lines, and am pretty sure that the fellow buying the 86 tub agrees.

What options do I have for mating the front and rear 86 lines to the 73 center tunnel lines?

[E Sully]

I made a bracket and installed the '86 fuel pump up front on the cross member. I then bought some fuel line and metric fittings from BAT and connected it to the '86 fuel filter on another bracket I made to replace the stock one in the engine compartment. I just used the stock tunnel lines. No problems were encountered. Does your 73 have both supply and return lines?

[E Sully]

It's been working great with no problems.

[gregwils]

I don't know if the '73 tunnel is the same as the '86, but I just pulled new lines last weekend. My motor and steering rack were out, so the additional effort was modest.

Here are some options....Fuel lines in Tunnel?

[Shaun @ Tru6]

Thank you Ed and Greg.

Ed, so you have simple hose clamps going into/out of the front and rear tunnel lines?

Seems like a bear to put in new lines, but one of those things where you just do it once.

[E Sully]

I used fuel line rated for fuel injection and hose clamps. It's a little tight, but works well. Fuel pressure for the '86 is also lower than the '73 cis.

[Gogar]

Shawn,

Where do you have the fuel pump on the 73, and what kind of pump? CIS or MFI?

IMO it would be a great time to move it up to the crossmember, if you have not already. Get it out of the wheelwell.

IF you want to use a high pressure (a-la CIS) pump for the 3.2, then you will have to pull the metal send line from the tunnel and replace it with the hard plastic CIS line; many folks don't like any kind of clamps on the pressure side of a CIS pump, although it was that way for years on my '72 and I wasn't the wiser.

If the motronic pump is lower pressure and you put it in the front, I don't know if folks recommend running a new line or using the metal send line that's already in there.

[E Sully]

The front cross member is a better place for the fuel pump, no engine heat.
If the steel lines are not corroded there is no need to change them. The 73 cis used hose clamps, and it ran at higher pressure than the motronic.

[Shaun @ Tru6]

When I had the carb set-up, I put the Pierburg fuel pump up front, and I'll be adding the Al crossmember from the 86 as well, just for the easier pump mounting of the motronic pump.

Looks like I'm just going to go with hose clamps, though I may flare the tunnel lines if I can. They are just flat metal tubes and I'd feel better with a flare and clamp set-up.

[spuggy]

Originally Posted by Gogar

IF you want to use a high pressure (a-la CIS) pump for the 3.2, then you will have to pull the metal send line from the tunnel and replace it with the hard plastic CIS line; many folks don't like any kind of clamps on the pressure side of a CIS pump, although it was that way for years on my '72 and I wasn't the wiser.

If the motronic pump is lower pressure and you put it in the front, I don't know if folks recommend running a new line or using the metal send line that's already in there.

Bosch just make fuel pumps. The pressure *capability* of a pump is irrelevant; a pump suitable for use with CIS is entirely suitable for EFI as well, because it is the regulator that determines the system pressure, not the pump.

From the Bosh "Motorsport Components", "Fuel Pumps" document:

Modern electric fuel pumps are “Positive Displacement” type pumps, this means that the pump cannot produce pressure unless it is acting upon a restriction. The only restriction in the system should be the fuel pressure regulator. The regulator controls the system pressure; the pressure ability or flow volume capacity of the fuel pump will not alter the system pressure.