Filling Tanks--Fuel Cutoff

[Chris Kennedy]

Hi:
As I "learn" more about my GT40 MKII, I am now turning to the subject of filling the gas tanks. So far I have been putting in gas in discrete volumes of 5-10 gallons, and am now ready to take the big step of filling until "full", as if it were a normal car----this sounds like a dumb question, but when filling at a typical gas pump will the pump automatically shut off when the tanks are full in these cars? Typically, I take off both caps, and fill from the driver-side intake. Any tips/warnings are also appreciated.

Thanks!
/s/ Chris

 

[Rick Merz]

Yes, near the tip of the nozzle is a small hole, and a small pipe leads back from the hole into the handle. Suction is applied to this pipe using a venturi. When the tank is not full, air is being drawn through the hole by the vacuum and the air flows easily. When gasoline in the tank rises high enough to block the hole, a mechanical linkage in the handle senses the change in suction and flips the nozzle off.

Are your tanks connected? If so there may be a lag for the opposite tank to fill so you may have to wait for the tanks to equalize and add more gas to get both tanks to the same level.

Rick

 

[DaveM]

Rick is right about waiting for the second tank to fill with the crossover pipe. I have to hit the nozzle multiple times as it keeps shutting off too soon. Finally I remove the nozzle and barely hold it into the filler to get the last 3-4 gallons in. You should be able to see gas come up into the filler tube. Should hold about 22 gallons.

 

[Chris Kennedy]

Thank you both--yes, I do have the crossover piping and I have noticed the slight delay in loading the opposite tank, even just adding small amounts of fuel. I feel sort of silly asking whether the nozzle still shuts off automatically, but have learned to ask anyway. I also appreciate the quick response AND the description, Mr. Merz, of how the nozzle actually works!

Thanks!
/s/ Chris

 

[Rick Muck- Mark IV]

Better to ask and not have fuel spilling all over your car than not ask! I find the crossover rate is about 1/3 of the volume going into the tank being filled so it does take some time to get both tanks full.

 

[Rick Merz]

There are no silly questions since we gain a bit of knowledge with every question that we ask. Many times we ask just to get confirmation or alternate solutions to our task at hand.

 

[Bill Kearley]

I will not rely on any automatic shutoff ( other than my pic-up or the wife's car ) as there is all to often a slight delay or splash. I'll be holding the handle and filling each tank and not waiting for the crossover. You MAY get away with a very slow fill rate on automatic if the handle has one.

 

[Neil]

I had the same concerns with a small mid-engine Sabel sports racer that I built. I found two mechanical float level gauges and mounted one on the top cover of each tank. Watching the gauge needle as the tank filled was far easier than peering into the dark filler neck to see the fuel level. The gauges were an aircraft part but I have no idea which plane it was used on.

 

[Chris Kennedy]

I intend to take it really slow (and I have been doing that even putting in discreet 5-10 gallon batches). Basically, what I do is manually hold the nozzle slightly open so it it is filling slowly, like I do in the '65 Mustang I have, which my father bought when new (when the Mustang was new, not my father). I just was wondering if I would feel it want to click off automatically, again like with the Mustang so that it doesn't spit back, like the Mustang, or "up", in this case. You know, what is it about GT40s and '65 Mustangs which just go together----the movie "A Man and a Woman", a Glescoe track video I was watching the other week, etc.?

/s/ Chris

 

[Dave Hood]

Based on my seven years of Superformance ownership.... Before you fill your tanks, make sure you take the caps off both fuel inlets. I've also found several gas stations where I can pull up to the pump (on the right) and the ground slopes down a bit to the left. This really helps promote the flow of fuel through the cross tube.

 

[Chris Kennedy]

Based on my seven years of Superformance ownership.... Before you fill your tanks, make sure you take the caps off both fuel inlets. I've also found several gas stations where I can pull up to the pump (on the right) and the ground slopes down a bit to the left. This really helps promote the flow of fuel through the cross tube.

Thanks, Mr. Hood--- your suggested technique worked great and the fuel tanks filled totally and the gas gauge actually behaved like a normal gauge for a change. Over about 140 miles of driving and three topping off fills at the same pump I was able to get a reliable calculation of fuel used/mpg.
Regards,
Chris

 

[DaveM]

One thing to be careful about is don't run the tanks too low. I did once and calculated that 1.5 gallons in each tank is about the limit where the pump won't pull anymore gas out of the tanks. That's just above 1/8 on the gauge.

 

[Chris Kennedy]

Yeah, I have read about that other places, which is one of the reasons I needed to get some feel for the gauge and the mpg of the car, itself.

Again, thanks,

Chris

 

[Tom Democko]

So Chris, what have you determined about miles per gallon from your car? What size engine do you have and do you know what your final gear ratio is?

 

[Chris Kennedy]

I have a Roush 427 SR with ZF 5 spd with 3.78 rear and .646 5th. The average over the two runs totaling 140 miles was 15.6 mph. It was mostly on I -10 W out of Houston. The car has the Speedhut speedo, and I calculated mph in 5th at 32.4 mph per 1000 rpm using the Wallace Racing converter calculator, and revs and speedo were spot on.

This is exactly the sort of driving I like to be doing while I figure the car out, and it gets run in.
Chris