Late Tank Early Car - Help

[Neunelfer]

Hi Gang,

Has anyone ever put one of the late model gas tanks in an early car? I'd like the extra capacity.

I have a 71 RS Clone (T based). The new tank is out of a 1987 car. I have both tanks here now and I noticed a fairly large difference in the connections.

My current connections are a banjo fitting for the return and the screened outlet both with female screw fittings on the tank. Both are toward the center of the tank.

The new tank has a simple press-on clamp style outlet (I'm guessing outlet due to the size) and a screw on (male this time) return. Both are toward the outside of the tank.

I'm guessing the outlet on the new tank won't be a problem. Is there a fitting for the return line that I can put in-line?

Any advise from anyone who's BTDT is greatly appreciated.

Thanks!

E.

[rst73]

Eric,
Give me a call at my new work number, 714 546-6939 ext.14
All the best!
Roger Grago

[911pcars]

I posted a reply to your question on PParts forum first. Forgive me.

Sherwood

[Neunelfer]

Thanks Sherwood,

I'm wondering why no need for a return line with carbs? My fuel pump (stock) has a return line in it... Seems like you need a return, but evidently not.

Fill me in.

E.

[ttweed]

I'm wondering why no need for a return line with carbs? My fuel pump (stock) has a return line in it... Seems like you need a return, but evidently not.

You don't need it with carbs, because of the low fuel pressure used (3.5-4.5 psi) compared to MFI or EFI injection, but it is still a nice thing to have. A recirculating fuel system keeps the gas cooler in the fuel rails and float bowls on the carbs, and can help prevent vapor lock and percolation problems. I have a later tank and return line in my '73, which Alex (RussianBlue) had installed with the 3.0 SC engine he had put in it, and when I went with PMO 50s on a 3.4, Steve Grosekemper at Dieter's plumbed them as a recirculating system when we put the new motor in the car.

TT

[911pcars]

Tom,
I'm sure recirculated fuel in the lines stays cooler. However, I'm not so sure the fuel inside the float bowls is heated from the same source; that being more of a function of heat transfer through the intake manifold and carbs. A return line can't hurt though, but you'll have to plumb in a return line if one doesn't currently exist. If you already have a return line, then it's a simple matter of connnecting it to a later tank.

E,
To prevent vapor lock from a hot soaked engine, a low cost computer fan on the underside of the grill controlled by a thermal breaker might be all that's needed. Have you installed the PMO heat insulators and performed the anti-percolation modification? Personally, I haven't yet had a need for any extra cooling. YMMV depending on many variables.

Sherwood

[ttweed]

Tom,
I'm sure recirculated fuel in the lines stays cooler. However, I'm not so sure the fuel inside the float bowls is heated from the same source; that being more of a function of heat transfer through the intake manifold and carbs.

You're probably right about this, Sherwood, I was just thinking if the fuel stays cooler in the lines, it can absorb more heat inside the carbs before reaching boiling point. The heat insulators on the manifold are certainly a key ingredient for keeping the carbs cooler. The RVP of today's readily available fuels has increased so much since these cars were built that volatility is a real issue.

TT

[Neunelfer]

Well... having the current factory fuel pump and factory lines, I already have a working return system. I'll just find the proper adapters to make this new tank work.

I'll call Roger again today to see what he has to offer.

Thanks guys!

[ttweed]

I'll just find the proper adapters...

Pegasus should have them, or Earl's. Roger might be able to have custom lines made up for you, if you specify the length and the fitting on each end.

TT