32/36 DFEV on 78

[architect]

Greetings,

I'm about to replace my fuel lines with braided (from front to back).... and came across a thread regarding 32/36 DFEV conversion.

Is it true that a fuel return wont be needed? If so, this could save 120+ bucks in braided lines / fitting.. and I could put that $ towards a fresh carb.

Would anybody agree this is a good move? (upgrade, downgrade, wash?)

Thanks!

[MattVAS]

It's not that the 32/36 doesn't need a fuel return....
It is that the 32/36 doesn't have a return line on it. This is really Weber's way of slowly trying to move everyone to using electric fuel pumps.

[architect]

It's not that the 32/36 doesn't need a fuel return....
It is that the 32/36 doesn't have a return line on it. This is really Weber's way of slowly trying to move everyone to using electric fuel pumps.

I see. Clever.

I swapped out to electric a few months ago.. so I'm getting closer?

[architect]

So just curious - do you need a return fuel line with an electric fuel pump?

I installed a Facet square pump. Big reason asking, I am about to pull the trigger on new braided lines, and don't want to waste the extra 150-200 on fittings / lines on the return.

[architect]

So just curious - do you need a return fuel line with an electric fuel pump? On the stock 34 ADF? Vapor lock?

I installed a Facet square pump. Big reason asking, I am about to pull the trigger on new braided lines, and don't want to waste the extra 150-200 on fittings / lines on the return.

[architect]

So just curious - do you need a return fuel line with an electric fuel pump? On the stock 34 ADF? Vapor lock?

I installed a Facet square pump. Big reason asking, I am about to pull the trigger on new braided lines, and don't want to waste the extra 150-200 on fittings / lines on the return

[AndyVAS]

Check your fuel pressure. A Weber carb doesn't like more than about 3.8 PSI. If you have higher, then you need a return line to bleed off pressure or you need a fuel pressure regulator.

[architect]

Check your fuel pressure. A Weber carb doesn't like more than about 3.8 PSI. If you have higher, then you need a return line to bleed off pressure or you need a fuel pressure regulator.

Ah okay! So if I'm understanding this correctly - the mechanical fuel pump is driven by the motor - which provides more pressure at higher rpm... thus needing a fuel return to maintain pressure (3. and "by-passing" the extra pressure back to the tank.

If using electric pump, then you run can run a regulator to keep constant pressure (3. and elimate the fuel return all together. (Which I like better?)

So I'm assuming that replacing just the fuel supply line, adding a FPR (which I already have) and deleting the return will be acceptable, regardless if I decide to keep the 34 carb or replace later with a new 32/36 carb???



Or am I completely wrong? Haha

[architect]

Duplicate post

[AndyVAS]

Mostly right. If your electric pump doesn't provide more than 3.8psi you can skip the regulator and return line both.

[nelsonj]

Hmm... I have a 32/36 with a mechanical pump and NO return fuel line. My car runs great - but I don't get great gas mileage. I'm not sure there is anything I should (or can) do differently. Any chance my not-so-great mileage has something to do with over pressure/no return line?

Thanks.

[AndyVAS]

If you are getting too much pressure it can force past the needle and seat and over feed the motor. Since this would only happen at higher RPMs and maybe only a little, you could feel to run well but suffer a significant loss in MPG. I would check your pressure by holding the pedal down so the motor free spins at around 4k RPMs. At that RPM for 30 seconds to a minute you should easily see a pressure spike or maybe even see fuel spitting out of the top of the carb before being sucked back in.

[nelsonj]

My car revs at 4500 at freeway speeds so it's definitly spending a lot of time where there may be an issue.

Question: should I put a pressure regulator between the fuel pump and carb to eliminate the issue? If so - does anyone sell such a regulator to keep me at/below the magic 3.8 psi?

Very interesting thread, always more to learn I guess.

[architect]

So... not providing a return line = deadhead config

I am reading about un-even pressures and possible wear on the pump. Is this something I should be concerned about? I would understand if you had a 10-12 psi pump, but the Facet only pushes 4 lbs, and I am only restricting by .25 lbs or so..

What do you think?

[AndyVAS]

You want a regulator as close to the carburetor as you can get it while supporting it from something other than the feed nipple.

Are you making exactly 4 psi? Most pumps have a range that they run at. Most of the low pressure pumps are 2.5-4.0psi.

A bypass regulator is considered best but I've seen simple regulators run for tens of thousands of miles and the pump behind it was still going strong. You can find countless regulators on the market with all kinds of fittings, adjustments, and gauges. Do a bit of reading and decide on the style you want and then find the regulator you like best.