Finally some Dany's Mag swap progress, and fuel line routing questions?

So we FINALLY got to the track this year and wow did the drag radials and slapper bars make a difference!! (Hats off to @318willrun!!)
The car is solidly in the mid 13's now when everything goes right, but...
We drive an hour one way on the interstate to the track, and by the tome we get there it is HOT!!
First pass you could hear it running out of fuel at mid track, we think because of the fuel boiling in the line where it goes next to the header on the pass side on its way to the pump.
and its running on what is in the float bowl for the first 3rd of the track or so.

We fought this a little last year, but then had an "Orange Box" crap out on us and spent time diagnosing that first.

Last year the fuel system got a new carter mechanical "race" pump and we insulated the fuel line for the 2 feet or so it runs along the lower inner fender, right by the Dougs headers.
It is still the original 5/16 line.

If we let the car set for an hour at the track, it makes a perfectly normal 13 sec pass, once..
if you hot lap it, it falls over at mid track again.
let it sit another hour, perfect pass, once..

So the plan is now to upgrade to 3/8 line, route it on the outside of the subframe and up the outside of the subframe connectors to the front of the car and into the engine compartment at or ahead of the pump to minimize the amount of line in the engine compartment.

Our question is, where is everyone else that still runs a mechanical pump running the line past the front suspension to keep it out of the engine compartment?
Thru the wheelhouse behind or under the upper control arm?
Thru the subframe itself?
Curious what others here have done.





Dany was so mad after that pass with the VW, She was like " I tree'd the **** out of him, if the car hadn't laid over I would have beat him and he has a faster car!!

This has been so much fun!!!

Personally, I'd get a return line plumbed in first if you don't already have one. Then use a 3 nipple fuel filter after the pump, that way you are constantly circulating fresh, cool fuel through the line and it doesn't have a chance to heat up and start vaporizing. You may not end up needing the 3/8 line. But if you really want the 3/8" feed, I'd still use the original 5/16" line for a return.

You know, Nick my youngest and I were discussing that very thing with the 3 nipple fuel filter.
I already ordered a 3/8 sender and it has a 1/4 return/vent nipple on it so that wouldn't be too hard to do.
If we use the current supply line as a return, would you still move it out of the engine compartment to keep it from pre heating the fuel on it's way back to the tank?
Or am I over thinking it??

Have you tried duplicating this on the street?
Does your fuel tank have a vent?
I am still running stock 5/16” fuel line in stock six cylinder routing in my 75 Dart Sport. Not same body as yours, but supplies plenty of fuel to run mid 12 second passes with a 400 cube big block. I doubt your fuel line itself, size or routing, is the problem.
I had the same symptoms on two different GM F-body cars. Both were immediately, although temporarily, fixed by removing the fuel tank filler cap. Long term I had to add a vent.

motorpirate said:

You know, Nick my youngest and I were discussing that very thing with the 3 nipple fuel filter.
I already ordered a 3/8 sender and it has a 1/4 return/vent nipple on it so that wouldn't be too hard to do.
If we use the current supply line as a return, would you still move it out of the engine compartment to keep it from pre heating the fuel on it's way back to the tank?
Or am I over thinking it??

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I'd just use it as is for now (I'm basically lazy), I don't think you'd have any issues using like it is as a return. Any vapors just vent back into the tank. Just make sure your tank is venting properly.
Just remember that with most, if not all, repro fuel senders there are issues with the sender accuracy. Not a huge deal, just be aware.

I never fixed this on my Challenger, would drive 60 miles to the track then drain the radiator and refill,
then get back in line. Long ride on the interstate warms up the whole car, quickest way to fix it is to dump all the water and refill. Otherwise I'd have to wait about an hour to make a decent pass. Much easier to dump the water and start over. I think moroso or somebody used to make a quick take apart for the upper hose that I saw on the serious racers. Of course they weren't running a thermostat either!

Bobzilla said:

Have you tried duplicating this on the street?
Does your fuel tank have a vent?
I am still running stock 5/16” fuel line in stock six cylinder routing in my 75 Dart Sport. Not same body as yours, but supplies plenty of fuel to run mid 12 second passes with a 400 cube big block. I doubt your fuel line itself, size or routing, is the problem.
I had the same symptoms on two different GM F-body cars. Both were immediately, although temporarily, fixed by removing the fuel tank filler cap. Long term I had to add a vent.

Click to expand...

I thought the same thing about the line size, but if we are redoing it, there is no kill like overkill, right?
Being a '66 it has a vented tank and not a vented cap. the vent is clear.
so far it can't be duplicated on the street, it really falls away at the top of 2nd and with trafic around here you can't stay in it long enough for it to nose over.

anyone have a part # or application that uses a 3 line filter?
Like 3/8 in and out with a 1/4 or 5/16 return?

This link has some numbers for 3/8 in/out and 1/4 return.
3 port fuel filter - (gmcmhphotos.com)

motorpirate said:

I thought the same thing about the line size, but if we are redoing it, there is no kill like overkill, right?
Being a '66 it has a vented tank and not a vented cap. the vent is clear.
so far it can't be duplicated on the street, it really falls away at the top of 2nd and with trafic around here you can't stay in it long enough for it to nose over.

Click to expand...

Nothing wrong with overkill, for sure. Hope you get it fixed quick.

My '82 B150 318 had a 3 nipple filter, was probably 5/16" but worth looking for.

sccachallenger said:

My '82 B150 318 had a 3 nipple filter, was probably 5/16" but worth looking for.

Click to expand...

I'm finding the 5/16 ones pretty easy, not so much the 3/8 ones so far...
Lots of good part numbers from Prof Fate, but so far no onne that actually has them in stock..

motorpirate said:

I'm finding the 5/16 ones pretty easy, not so much the 3/8 ones so far...
Lots of good part numbers from Prof Fate, but so far no onne that actually has them in stock..

Click to expand...

I just remembered one issue I had with the van. When the fuel level in the tank was low the engine would run rough.
I closed off the return line to the tank, and the problem went away. Hopefully you won't see that problem!

So my Googlefu is usually pretty good, but I am not finding anyone with the 3/8 filter with the return in stock (except 1 GM restoration place, $149..lol)

But I am finding lots of the 5/16 version for $6 or $7.
I have a 3/8 sender on its way with a 1/4 return fitting.

Would we be nuts to redo the system in 3/8 from the tank all the way to the pump, with a 1/4 return, then leave the existing 5/16 line to the regulator and from the regulator to the carb so as to be able to use the 5/16 filter?

Maybe a better question, should the 3 port filter be before the regulator?
Currently the filter is AFTER the regulator.
If we put it BEFORE the regulator it would end up standing upright, under the alternator.
It seems to me that 3 port filter would work better standing upright with the 1/4 vapor return on top.
The plan is to try to run the lines on the outside of the subframe as far as possible, maybe going on the bottom of the subframe to get around the front suspension?
has anyone here run them anywhere but on the inside of the front subframe (factory location)???
this was the only pic of the regulator/filter I had on the computer at the moment.

thanks guys!!