Drag race fuel system

[Glen]

ironic.  I ran an orange Henry J Saturday and the gentlemen was explaining the problem to me.  After I ditched his full race car on the starting line I knew his problem still existed.

When I added my new Pro Systems carb last week the builder explained to me that i may have to change fuel pumps.  He explained that when releasing the transbrake, the inertia may push the fuel back toward the tank and suck a vacuum on the float bowl......He told me if I had that problem I should change my fuel pump setup to a bigger capacity.
He was saying that problem usually pops up when a 60 ft time is less than 1.5

[Crosley.In.AZ]

thanks for the replies and idears.

As I mentioned everything has been looked at , changed , altered ... cept for the fuel system.  We initially were so sure this crapping was an electrical problem , that is where we focused the attention.

We figured the Holley blue pump would feed two Holley 450cfm carbs or the Carter cabs that were on the car earlier.

The fuel tank is vented well.  

MSD tech has been called a few times.  The MSD box is wired ( positive and negative) directly to the battery in the back of the car per the tech line.

As I posted earlier the chassis dyno computer indicates there is no mis-fire in the ignition system when the motor craps out.

Glen,

The Henry J should run in the mid 11's  around 115 - 120 mph.  Shifts at 7k, through the lights at 7300- 7400 rpm

[enjenjo]

You might want to check that the engine had a good ground. Under load strange things can happen with grounds. It may not show up on a dyno, but only under accelleration.

[GPster]

That accelleration thing brings back memories of tech acticles. Is the engine carburated? What about what happens to the fuel in the float chamber? Also, using old technoligy. what are the differences between the atmosphere wher the dyno is and the drag strip? I imagine there is a cooling fan in front of the car on the dyno. At the strip you're dealing with stagnant under hood airwith a different outside temperatureand sun beating down. How about altitude? Is it giving him different fuel/air ratios than the dyno room? GPster

[C9]

I've read the bit about fuel inertia on a hard launching car.

Usually worse with big lines - 1/2" and up.

Now that I think about it, the fuel line on my 32 is #8 from splitter to carbs whether dual Carter 500's or single Edelbrock 750.
The single Edelbrock 750 has run both #6 and #8.

Shown in the pic above is #6 all the way - bit of a lashup when the mechanical pump first went on.
The line from oil fill cap on rocker cover is a #8, no big deal, but just for comparison.


Any possibility the vent gravity check valve ball is upside down?

Wondering too if the dual Holleys are oriented sideways?
As well as what kind of floats - center pivot or side pivot?

I remember AFBs having a problem in corners where one float chamber went dry and the other flooded due to centrifugal force on a hard corner.
Seems like Holleys may have had a similar problem with side pivot floats on a hard accellerating car.


You said you pulled the chip on the MSD?

On my 6AL with built in rev limiter, chips are changeable and I believe it comes with a 3000 rpm chip - and some others with higher RPM ratings.

The 3000 rpm chip is for testing and I found it to be just the thing when someone else took the car for a drive.

I'm not sure what happens when the MSD doesn't have a chip plugged in.

Little brothers HJ did the stumble off the line bit when it was running a 468" Olds, 850 Holley double pumper.
I believe it ran a Holley blue pump, not sure about a regulator.
This was when the car was running mid-10's.

He got into a stumble problem at launch on a hot day at Famoso.
The problem was determined to be flooding, but for the life of me I can't remember how he cured it.

At the time I tried to convince him that a vacuum secondary carb would be a much better way to go, but at the time, he was like a lot of guys and if it ain't "Official Drag Racing Stuff" he didn't want to run it.

He's gotten over that now.

If you have access to a different pair of carbs or even a single intake with one large carb I'd give that a try.

I'm still thinking a fuel pressure gauge would tell you a lot.


Here's some pics of little brothers HJ fwiw.










500" DRCE engine with Olds billet heads, aluminum block, 6800 rpm chip at launch, 9000 rpm chip on the top end, Lenco trans.

8.13 @ 166 mph.

[Hooley]

WOW, Little bro's Henry is Top Drawer.  I had a problem off the line with a rich condition due to fuel being pitched out of the carb vents and down the carb. It would pick back up and run to the end.  I fixed this by running a tube from the front bowl vent to the rear vent with holes in the middle. Problem went away.  I believe their problem was running out of fuel futher down the track.  Hooley

[Crosley.In.AZ]

Fuel system on this Henry J has been modified .  Filter is now after the pump on the side of pressure to the carbs.

There was a 50 - 50 split on the filter before or after the pump...  previously the filter was before the pump.

Plumbing to the carbs was split off the pressure regulator , one line to each carb.

Dead head pressure test of fuel pump shows 14 psi...  flow test of Holley pump  shows correct amount  at 1/2 gallon of fuel in 20 seconds.  I think that is a low amount of fuel in 20 seconds for this car.

These are 450cfm Holley carbs.. side hung floats.  The J does not bog off the line , the engine starts crapping at 5500 rpm in each gear.

[Glen]

FYI....Firebird is running their friday night "Run what you brung" program on Friday and Saturday this weekend.  Should make for a nice saturday night with fewer cars than a normal friday night.

We are taking both cars.  I am trying to get in more tuning time before it gets hot and starts going backwards.

[C9]

The good dyno runs probably disprove this, but I'll toss it out anyway.

Run the engine in a dark place and see if the plug and/or coil wires are flashing over to ground.

Found one hard to diagnose problem this way.

Seldom happens with todays quality plug wires.


Any chance the coil wire is long and perhaps flailing around due to airflow through the engine compartmet?
And maybe going to ground?

Sometimes too, things look ok and closing the hood can create a problem with long wires.
Kinda doubt this one, but it happens now and then.

[C9]

Getting back to the fuel problem, what kind of fuel cell are you using?

Or is it a tank?

I'm wondering if something can be floating or rolling around inside the tank and shutting or slowing fuel feed under accelleration.

If it's a fuel cell, more than likely that wouldn't be a problem.

Most of the race-o fuel cells have #8 outlets and vent which is sufficient.
Even a #6 line works fine as a vent when the main feed line is #8 all the way.

I had a fuel cell in my 32 - first cell tried, vertical like a 63 Chevy half ton pickup - and it had #6 outlets at each bottom end.
You were supposed to use one end and plug the other, but I ran both into a home-made fuel block and went #8 line from there to the regulator.

That tank got swapped out in a matter of days because the fuel filler system was a quick and dirty deal and leaked - not quick and dirty by me, but by LTL.

If a cell and I'm betting it is, is it the drag racing style with bottom sump and outlets?
Those work great at the track.

The circle burner type fuel cells have a top outlet with the pickup plumbed to a rubber fuel line that's placed in the right rear corner bottom of tank and then the cell foam is added so as to hold it in place.


If the pickup was installed in the wrong place and maybe even pointed up I can see where the fuel system would work ok in a static situation like a dyno, but become 'uncovered' by fuel under accelleration.

Your vent system is probably ok, problems there usually show up farther down the track if there's a clog or semi-clog.

One thing that gets a lot of guys is a 'flapper' in the fuel line.
Not so much of a problem due to the way Earls braided lines assemble on the re-usable nipples, but you can still get em if you're not careful.

And before you tear into stuff, get a fuel pressure gauge in the car so you can check pressures under accelleration.
They're a great diagnostic instrument and I run em in the hot rods along with a vacuum gauge which is great on a street runner, but not necessary on a drag racer.

Use an isolater as noted before.
Auto-Meter has a great combo with both gauge and isolater in the package.

In my opinion, a fuel pressure gauge is 2nd only to the oil pressure gauge in importance....

[wayne petty]

i know its expensive...     but if it has a fuel cell...  has it been tried with an almost full cell...     not just the few weight saving gallons most people run???

perhaps there is only a problem do to the low fuel level...

[C9]

I read back through the posts.

Are you running the small Holley pressure regulator?

I note you're using the regulator as a fuel block also.

Any chance you got one of the flathead, 97 Stromberg low pressure regulators?
They drag pressures down to about 2.5# - 3# or so.

Seems like the small Holley regulators we see on everything may not have the capacity required.
I say that cuz I see lots of dual quad installs where they run one of these regulators before each carb.

Probably a "looks cool" deal instead of a necessity, but maybe it is required on some big CID engines as well as those who turn some high RPMs as your engine is doing.

Could be more restriction in these than I think and that's why two of them on the dual quad setups.

Right now, I'm running the small Holley regulator on the 32 and it's working ok with the single 750 Edelbrock and 4 1/2# - 5# at the carb.

I seldom run the engine over 5000 rpm so I'm not requiring the fuel volume you guys are, but with the big engine it's probably not too far behind.

Thinking too that 14# on the regulator inlet side is way too much for the carbs if, big if here, the regulator is defective and not regulating as it should.

Even so, the defective regulator should have shown up on the dyno pulls.

You've probably already done it, but if not I'd check float levels, especially the secondaries.

That's one place that stumbling can occur under accelleration, but not on a dyno.

Nuff for now - need more coffee....

[Crosley.In.AZ]

HI,

the Henry J has a fuel tank of aluminum with sump at rear of tank.  Tank is new

I have learned and never noticed on t he car... my budddy had the pressure regulator on the frame under the passenger door.

it was explained to him the regulator needs to be close as possible to the carbs , then split off each side of regulator to each carb.

he had the regulator on the frame under the door, with one line feed forwar to a Y  that split off to the carbs.

System has been replumbed , larger line from tank to pump... then filter , then #8 line up to the engine bay where regulator is... #6 line to carbs off each side of regulator.



 :?  

[Crosley.In.AZ]

FYI....Firebird is running their friday night "Run what you brung" program on Friday and Saturday this weekend.  Should make for a nice saturday night with fewer cars than a normal friday night.

We are taking both cars.  I am trying to get in more tuning time before it gets hot and starts going backwards.

hi Glen,

I have the Falcon apart for more changes.  I will mod the log manifold for better flow.

I would like to have an aluminum cyl head with intake , but there is no money for that.. about 2500.00

[HYPORX]

Just got here...

If it's not fixed by the next run, get him to shut down after it begins and coast through the traps in neutral.
I want to see a photo of all the plugs, numbered if possible.

Sounds to me like fuel starvation, I just want to see how bad it is.