Fuel tank sending unit for more HP

All.

I installed a reproduction gas tank and sending unit, and I am going to run new fuel hard line. Currently it has the stock 318 but I can see more cubic inches in it future (360 or 390 stroker possibly).

I want to run 3/8" hard line to feed the larger cubic inches in the future, the problem is that the tank's sending unit is only 5/16" line.

Is there a sending unit that will work on a stock tank from another vehicle that has 3/8" line that will also has the same ohm rating as the original?

What are you HP and big block guys doing?

Thanks...Keith

A cure for a line change is an electric fuel pump. regulate up front, as the engine needs the electric pump will provide faster than just a larger line will.

I'd suggest removing the sending unit, bending up a new 3/8" pickup line, drilling a hole and soldering, brazing or welding this into the sending unit. The original line can be used as a return (high HP electrical pump) or sealed off. Don't forget to increase line size the full length of the run and putting a pickup sock on the end of the new pickup.
if this is race only, you can install a sump with hose fittings to the bottom rear of the tank.
https://www.summitracing.com/parts/cee-4041?seid=srese2&cm_mmc=pla-msn-_-shopping-_-srese2-_-competition-engineering
This is not legal for the street (would drain entire fuel load if damaged), and requires welding.

Guys, Thanks for the great ideas / information. It gives me some ideas.

Keith.

I'm installing a 410 stroker and having researched the possible need for upgrading the fuel supply decided to add the Carter P4594 electric fuel pump (Rock Auto has best price) along with the Carter M6866 mehanical with the oem 5/16" line. This cost about $65 total, and for street rodding around will be fine, once at the strip we'll see, probably will be alright, if not then I'll look into fuel line and sending unit upgrades. No sense in doing all that up front when it may not be needed. Cheapest route first for me.

lws67 wrote:I'm installing a 410 stroker and having researched the possible need for upgrading the fuel supply decided to add the Carter P4594 electric fuel pump (Rock Auto has best price) along with the Carter M6866 mehanical with the oem 5/16" line. This cost about $65 total, and for street rodding around will be fine, once at the strip we'll see, probably will be alright, if not then I'll look into fuel line and sending unit upgrades. No sense in doing all that up front when it may not be needed. Cheapest route first for me.

I would like to hear your results. My thoughts are that a 5/16" "straw" will not flow enough to feed a 750 or 800 CFM carb with big jets (or multi carbs). It seems like the float bowls will go dry at high RPMs no mater how high flow the fuel pump(s) is.

Please let me know... Also would like to know how you like the 410, should make tons of torque.

Keith D wrote:

lws67 wrote:I'm installing a 410 stroker and having researched the possible need for upgrading the fuel supply decided to add the Carter P4594 electric fuel pump (Rock Auto has best price) along with the Carter M6866 mehanical with the oem 5/16" line. This cost about $65 total, and for street rodding around will be fine, once at the strip we'll see, probably will be alright, if not then I'll look into fuel line and sending unit upgrades. No sense in doing all that up front when it may not be needed. Cheapest route first for me.

I would like to hear your results. My thoughts are that a 5/16" "straw" will not flow enough to feed a 750 or 800 CFM carb with big jets (or multi carbs). It seems like the float bowls will go dry at high RPMs no mater how high flow the fuel pump(s) is.

Please let me know... Also would like to know how you like the 410, should make tons of torque.

Absolutely, the main reason I'm going the original line etc is that I just bought a new repro sending unit, not really inclined to butcher it right off the bat, and that I ran a 64 Sport Fury w/ a built 440 and Holley 750 with only a Holley electric pump years ago and never had any fuel delivery issues with I'm certain 5/16 line, I may be mistaken  as it may we'll have been 3/8, but original regardless.. I'll be running a Demon Street Demon 750 (similar to a Thermoquad) and estimated 450 hp, hopefully low to mid 12's in the 1/4 mile. If I have to enlarge, will absolutely do it.

One other thing to consider along with the amount of fuel pushed forward to the carb is the weight of that mass.
Many guys running the strip upgrade in steps. They have found that with each upgrade, another problem may occur.
In this case, a big fuel line with a 'street' pump will also tend to starve for fuel at the top end. The reason is that the pump can push the volume and weight of the fuel in a 5/16" line, but the increase to 3/8" means a lot more effort is needed. This increases as E.T Drops due to the added G force. This might happen at 12 second quarter mile times. That's pretty quick. Only super tuned hemis and similar high HP cars did that back in the time of these vans, and they weren't pushing a barn door through the wind, requiring even more power (and fuel) at the top end.
Also, darn near every low priced mechanical fuel pressure gauge I've seen is pretty inaccurate. They need to be accurate at 0-10 PSI. I've had three on the same system read 1-3 PSI different. That's 10-30 percent off! Which one is right?

So, the first step is clean, leak-free stock setup.

Second step is an electric 'street' pump back by the tank pushing forward thru stock setup. Hopefully you are supplying power through a nice thick wire, since it's a long run. This should feed about 250-300 HP.

Third step is a biggie, because you are making a lot more changes. Most people tend to do this part in stages and have issues.
A 'race' pump fed with a relay, through bigger lines, using a good quality tested fuel pressure gauge (often with an isolator so you don't have gasoline at the back of the gauge where you can see it), with a pressure bypass/return back to the tank. The 'race' pump supplies a lot more volume and pressure than the carb can handle at idle and cruise, so you have to be able to tone this down. The bypass/return also helps keep the pump and fuel cooler and prevents vapor lock.

Forth step is when you are going a lot faster or running a big nitrous system, which requires 2 pumps.

I just did a search for this and found this article. I skimmed through it and it seems good. I'm sure there are a lot more out there.
http://www.musclecardiy.com/performance/holley-carburetor-fuel-and-fuel-supply-systems-guide/

I'd talk to guys in your area that run cars at least a second quicker than you expect your van to run to compare fuel systems. This should cover your extra fuel needs due to air resistance. Also, ask to see what they are running. We have all met the guy who says "it's all stock, just a 318" and runs faster than a 440.

Keith D wrote:

lws67 wrote:I'm installing a 410 stroker and having researched the possible need for upgrading the fuel supply decided to add the Carter P4594 electric fuel pump (Rock Auto has best price) along with the Carter M6866 mehanical with the oem 5/16" line. This cost about $65 total, and for street rodding around will be fine, once at the strip we'll see, probably will be alright, if not then I'll look into fuel line and sending unit upgrades. No sense in doing all that up front when it may not be needed. Cheapest route first for me.

I would like to hear your results. My thoughts are that a 5/16" "straw" will not flow enough to feed a 750 or 800 CFM carb with big jets (or multi carbs). It seems like the float bowls will go dry at high RPMs no mater how high flow the fuel pump(s) is.

Please let me know... Also would like to know how you like the 410, should make tons of torque.

OK, took a while, but results are in after a summer of 1/8 mile runs winding up with a 1/4 mile run last month. With the 5/16" line, and running both a recently installed the Carter strip mechanical and electric pumps there appears to have been no issues with fuel starvation running the 1/8 mile. Best times were 7.85@87.3mph, but the season ending 1/4 mile run showed fuel starvation a few feet from the traps. Best time was 12.19@107.6mph regardless. So 3/8" line is being installed to hopefully eliminate that, and maybe pickup some more mph through the traps.

Rather impressive, how did you get it to hook?

OutofSight wrote:Rather impressive, how did you get it to hook?

255/60-15 Mickey Thompson ET Street drag radials @16psi, MP adjustable pinion snubber just touching, pinion angle set, basically a dialed in Chrysler engineered leaf spring suspension, and studying the book "How To Hook And Launch" Best 60' time so far has been a 1.68, this run it was a 1.75, it was about 52 degrees that day. You can hear it running out of fuel at the traps and beyond  

Very impressive!

Low 12's in a A100 van (maybe high 11's soon?) that is freaking awesome!!!

Along with the fuel line upgrade, I'm swapping out the 3.73 gear for a 4.10, the goal is high 11's for sure!

I ended up disecting an old sending unit. Bent some 3/8" tubing to the angles needed, cut off the old tubing, drilled out the mounting plate to accept the 3/8,  then used a MAP torch and brazed it. Tried to salvage the sending unit but messed it up disassembling it. Carefully drilled out the plastic strainer, luckily theres enough meat to drill to 3/8" The heat needed to braze cooked the stud seal/insulator on the plate so I plugged that with a nylon washer and bolt. Being mostly for the drag strip who needs a guage anyway! I'll just keep track of the miles I put on it. Probably could have used some high silver content solder and done the same with less heat but it works.....

Nice work!

LWS67,
Awesome is right. Do you have a build thread here on VV? Would love to see it.

Lws67/12many,

Thanks, Great thread on FABO. Your van is very cool and really hot!

Richard

Yes, very good read. Congrats on a job well done 👍

Post deleted by Sweetvan.

nice!

Keith D,
Sorry for diverting conversation to LWS67. I will send him a private message. How is your project coming?
Sweetvan

sweetvan wrote:Keith D,
Sorry for diverting conversation to LWS67. I will send him a private message. How is your project coming?
Sweetvan

No problem at all... That's what I like about this forum, I learn all kinds of new information especially when things change directions some.

Help everyone learn new good stuff by keeping the questions and information coming.

Keith D

Keith,
Something that hasn't been mentioned yet is the vent on the gas cap or the vapor recovery system. Early Dodge vans had a vented cap that could leak gas when near full, on acceleration or right turns. If it was replaced with a non-vented cap, a vacuum could be forming in the fuel system, which could inhibit gas delivery and cause fuel starvation. You could find out if this was happening when you remove the gas cap; it would be difficult to remove and you'd hear a sucking sound as the vacuum was relieved. If a fuel vapor recovery system was installed, it would also need some way to relieve a vacuum by letting air in as the fuel is drawn down.
Richard