How To Measure Fuel Volume.

-
SpeedThrills

SpeedThrills

FABO Gold Member
FABO Gold Member
Joined
Jun 3, 2008
Messages
2,673
Reaction score
1,546
Location
Very South Jersey
I have about 15 runs on my street/strip Duster with maybe 350-380. HP, 3200 (actual) convertor, 727, 4.30 gears, and when I last ran it, 26" tires (It has 28's on it for the next trip.)
Only about half the runs were any good because of shifter problems. I shift it at 6k. I haven't gotten a good read on what it traps at. (See below. The laziness seems to make it vary a bit.)

It runs 11.80's @ about 109-110. It doesn't pull hard at the top end. No ducks, just seems to give up some. I think it should run about 113. (3000# at the line.) But I don't know.

Valve springs seem okay. It revs fine in 1st and 2nd. The pull just tapers off in high gear.

I'm looking through my fuel delivery. I have 1/2" (-8) line from the sock to the Blue Holley pump, through a Fram HPG-1 filter, and up to a Holley regulator on the inner fender. From there, it's 3/8 (-6) to the 750 Holley vacuum secondary (lightest spring) "Street Avenger" carb.

I checked to see if it was pulling vacuum in the traps, and maybe closing the secondaries. I have also checked for full throttle.

The float levels are okay. Fuel pressure shows 6 3/4 idling, a little over 6 in the traps.

To my question: How do I accurately measure volume? I know to pump it into a bucket. The easiest and safest way would be with the engine off and ignition disabled. Would the pump be putting out enough without the alternator putting out the 14.2 v it puts out when the engine's running?

What's a good flow per minute?

I'm also going to compression and leak down tests.
 
The bucket test will be the easiest. A holley blue pump is rated at 110 gph, Flows 88 GPH at 9 psi, so at 6-7 psi I'd think you'd want a little more than a gallon a minute as 9 psi is 1.46 gallons (88 pgh/60 mins = 1.46). I honestly don't think fuel is your issue. Can you provide more specs on your engine.
 
I agree with above.

I did not see carb combo posted.

Could it be lean or perhaps too much timing (suggest 34 total
to start at Sea Level). Both of those would be more apparent
in high gears as RPMS increase.

With the 26 tire or even 28 = It might be happier with 3:91 gearing

I would be interested in more details on your combo to give you better feedback.
 
Last edited:
Put a battery charger on the battery to raise voltage.

Or just start the car with fuel line in a can. It will run a minute before gas in carb runs out. Needs to run 15 seconds for the test.
 
I doubt you have a fuel system problem. I have almost the identical setup regards fuel system hardware( except my pump is a hair smaller than a Holley blue) and it should get my 3330 race weight to 130+ in the 1/4. Been close in really bad air already.
Although I think I have outgrown this little All star pump from Lane automotive( Motorstate)
What exactly is your combo. Sounds like a lot of gear with 26 inch tire if you don’t have much head on the car
 
Free flowing into a bucket off the regulator tells you nothing useful.
Under those conditions the pressure after the regulator is zero.

What matters is how much does the system flows while maintaining your minimum desired pressure.

For that test you need to put a valve at the end of the line going into the bucket.

Then you adjust the valve with the pump running so the gauge reads the lowest pressure you want to see(around 5psi).

Shut the pump off, don’t touch the valve.
Empty the bucket.

Have someone turn on the pump and time how long it takes to pump one gallon.

It’s pretty safe to use .5 lbs per hp/per hr for figuring fuel consumption.
Figure gas is about 6lbs per gallon.

So, if it takes 90 seconds to pump 1 gallon while maintaining 5psi, that’s 40 gallons per hour, x 6 = 240 lbs/hr.
240lbs/hr divided by .5 = 480hp.

All that said, If your system is maintaining 6psi thru the finish line, it’s unlikely you have a fuel delivery issue.
 
PRH said:
All that said, If your system is maintaining 6psi thru the finish line, it’s unlikely you have a fuel delivery issue.
Click to expand...

This. Put a fuel gauge on it that you can read while driving.

If you have 3.5 psi at WOT and 0.120” dia. fuel inlet valves, you can support well over 500 hp.

Based on you et verses mph, you could have a fuel delivery problem, iMO.
 
@SpeedThrills , what are your 330 and 1/8 mi times?
Agree, 11.80s should be close to 113.
Where are you getting your fuel pressure readings from? Before the regulator or after? Can you see the gauge during a pass?
 
If you have access, or can borrow one, I'd stick a double pumper on it.


Oh, and according to Wallace, you are around 64-6500 in the lights at 110 with 4.30 and 26"tires.
 
I'll try to address all of the ideas that have been posted!

First, I did a compression test (warm, throttle open), but haven't done a leakdown yet.
1) 180
2) 170
3) 185
4) 185
5) 170
6) 180
7) 170
8) 170

The entire drivetrain is out of a totaled Pro Street D150. It's a .030 360 that the seller didn't know much about, so I took it apart. It was all good so I reassembled it with new rings and bearings. It has the 750 vac carb I mentioned. I put the lightest spring in it. (Jetting info below.) Torker II, Unilite w/o vacuum advance, heads are 3418915's that have 2.02's, 1.60's and have been ported. I don't know anything else about them. MP 292* 508 cam, installed at 108 ICL (per Mopar Perf.). Total is 35*. I neglected to check valve spring pressure, but I haven't floated them. Crane gold 1.5 rockers. KB 190 pistons. I don't have the numbers handy, but the static compression worked out to about 11.1:1. I have no idea about dynamic compression. Hooker 1 3/4 (Part no. 5204, I believe?), w/ 2 1/2 H-pipe, Hooker Max Flo mufflers (no drone!), dumps.

It pulls 7" vacuum at 1200, out of gear.

I just checked valve adjustment the other day. They were good. About a half turn past zero.

I just took the line from the carb and put it in a gallon bottle. Turned the pump on and the jug was a bit over 1/2 full in 20 seconds. Seems good there.

The truck I took the drive line from had a 9" Ford rear with 4.10s' that were noisy. Being a Pro Street, it had tall (and wide) tires. Soooo, I put a 26" tire on it and 4.33 gears. Now I have 28" tires, that I haven't tried yet. Sounds like I am over-geared?

I don't record air conditions because it's a toy, but I guess I should. I ran it last summer and last fall. I used to race, and I would call the summer conditions "average". They weren't nasty humid summer days, but it wasn't "mineshaft". Jetting then was 72/76.
When I went in the fall, I used 74/78, but had no basis to do so. Jetting and air didn't affect the feeling of it laying down. Seems it was going 90's in the summer, and 80's in the fall. But I don't have enough good runs on the car to say for sure.

Fuel pressure readings are taken from the carb, where it splits from front to rear. I have a cowl mounted gauge that I can see on the track.

I'd like to try a double pumper. I'll have to make friends with the right person!

I cherry-picked 2 good runs from my fall outing.
1723244380797.png
1723244323384.png
 
Last edited:
Now that you have posted your combo, I can pretty much guarantee you a “ real” convertor would really wake your combo up all over the time slip.
Would be nice to know how good the heads truly are, but that cam is almost 250@50, it’s gonna pretty much be a dog at where the convertor you currently have is hitting at. It would probably like something 42-4500 for sure. Even more.
You mentioned the cam, from what I have seen, it’s ground on a 108, it’s likely gonna be most happy stuck in at 104. You didn’t install it straight up at 108 did you?
If my understanding of that cam is correct, the above could really affect the time slip too, especially with the vert you have.
 
113 with the 26" tires would be 6600 in the lights. With 28s, around 6100.i think the taller tires are a good move.
And (according to wallace) that 92 mph 1/8th pass should have been a 113, and about a tenth quicker.
Find somebody with a valve spring pressure checker for on-the-head.

And, I agree with ^^^^^^^. A 4200-4500 converter will be a dramatic improvement, .... if it hooks.
 
Also doubt you have a fuel delivery problem. More likely to have a problem in the lower gears where the fuel gets used at a faster rate.

I would be more worried about 7" of vac @ 1200 rpm. Seems very low...
 
B3422w5 said:
Now that you have posted your combo, I can pretty much guarantee you a “ real” convertor would really wake your combo up all over the time slip.
Would be nice to know how good the heads truly are, but that cam is almost 250@50, it’s gonna pretty much be a dog at where the convertor you currently have is hitting at. It would probably like something 42-4500 for sure. Even more.
You mentioned the cam, from what I have seen, it’s ground on a 108, it’s likely gonna be most happy stuck in at 104. You didn’t install it straight up at 108 did you?
If my understanding of that cam is correct, the above could really affect the time slip too, especially with the vert you have.
Click to expand...
I’m thinking a converter would help too. That’s not in the budget now.
Cam is at 108. Would 104 lessen top end charge more? It would probably help the idle, if nothing else.
I also would like to avoid getting to where I need a roll bar and the pita 2 year belts. That sucks doesn’t it? The rules, though for everyone’s safety, dissuade me from going quicker.
33IMP said:
113 with the 26" tires would be 6600 in the lights. With 28s, around 6100.i think the taller tires are a good move.
And (according to wallace) that 92 mph 1/8th pass should have been a 113, and about a tenth quicker.
Find somebody with a valve spring pressure checker for on-the-head.

And, I agree with ^^^^^^^. A 4200-4500 converter will be a dramatic improvement, .... if it hooks.
Click to expand...
Hooked pretty good with the 235 MT ET streets. I only have front clamped slant springs and loosened front suspension. 28’s are 265’s. Cal Tracs are the long term goal.

Bewy said:
“I would be more worried about 7" of vac @ 1200 rpm. Seems very low...”

That’s what it had before I tore it down for inspection. Hasn’t changed. Maybe the cam at 104 will help.
 
The start of the run is where improvements will have the most impact on the time slip.
I would guess that cam is suggested to be installed at 104, as most generally want the cam advanced 4 degrees.
That is where I would want it, especially with a stock stroke deal.
 
B3422w5 said:
The start of the run is where improvements will have the most impact on the time slip.
I would guess that cam is suggested to be installed at 104, as most generally want the cam advanced 4 degrees.
That is where I would want it, especially with a stock stroke deal.
Click to expand...
I’ve always been one for advancing the cam. But reading about this 292, I heard enough to put it straight up. But I like what you’re saying and I’m going to advance 4°. I like that idea. Besides the bottom end grunt, I’m guessing that increased cylinder pressure would help all the way down the track.
Plus, it’s a lot cheaper than a converter! This combo seems to have been put together pretty well. But the converter does seem dated. It seems like they tried to keep the stall low because it was a street vehicle. I haven’t used any, but I hear converters are way better than they used to be.
 
SpeedThrills said:
I’ve always been one for advancing the cam. But reading about this 292, I heard enough to put it straight up. But I like what you’re saying and I’m going to advance 4°. I like that idea. Besides the bottom end grunt, I’m guessing that increased cylinder pressure would help all the way down the track.
Plus, it’s a lot cheaper than a converter! This combo seems to have been put together pretty well. But the converter does seem dated. It seems like they tried to keep the stall low because it was a street vehicle. I haven’t used any, but I hear converters are way better than they used to be.
Click to expand...
I can agree with "pretty well". For a stock stroke 360 with a pretty mild cam, and not great heads it e.t.'s quite well, imo. Figure out the reason it feels like it lays down, it will get quicker too. (I don't believe it's a fuel problem either).
 
mopar race manuals, says have to pump 1 gal.in 25 seconds or less. that is Minium volume. i use a areomitive fuel pump and reg.and 1/2 line. just food for thought
 
Advancing the cam to 104 will shift the rpm range lower by about 200 rpm. It will improve idle quality & vacuum, but only by a small amount.
 
A few pulls on a chassis dyno to get a look at the power curve would probably answer a few questions.
They often have an o2 sniffer they can slide in the pipe to check the a/f ratio.
 
Bewy said:
Advancing the cam to 104 will shift the rpm range lower by about 200 rpm. It will improve idle quality & vacuum, but only by a small amount.
Click to expand...

It also will improve the bottom with that large ish
cam and smallish convertor, which will positively effect the Et slip.
Will create more torque around where his convertor hits.
For a cheap investment, I would also throw a 4 hole spacer on the car.
Especially with the single plane on it.
 
Last edited:
You must log in or register to reply here.
-

Back
Top