Holley/Demon Carb stumble

[Cudafever]

In terms of absolute capacity, CF’s fuel system has plenty of flow.
It’s way better than 85 seconds at 6psi....... so, fundamentally it’s fine.
At this point I’m just seeing if there is a way to adjust the regulator differently so there isn’t a 2psi system pressure drop when going from idle (9psi) to wot at rpm (7-ish psi)........ to try and minimize the float drop.

If none of that seems to have any impact on the laying down in high gear...... then the “what I would do” test would then be put the Demon completely back together, put it back on and verify that with the same bowls, and the floats adjusted the same way...... it doesn’t lay down 1/2 way thru high gear(after pulling strong through the first two gears).

This will happen eventually for sure.
but will buy proform bowls floats in the end. so i will have a legit Proform and Demon 850 carb.
Wife had cut me off on my spending spree, at least until my next paycheck
But i did buy the proform metering block that proform recommended, before she cut me off Shhhh

But anyway, back to proving my fuel system good or bad. When i get the time you will get the data.

 

[Cudafever]

I think he is focusing on what what the pumps can supply and how they interact with the regulator. View attachment 1715382130
I prob shouldn't answer for Dwayne though.View attachment 1715382131

I wonder if Mallory has some flow graphs at different pressures. I do have a little bit of Mallory tech liturature from 15-20 years ago. If the pump you have was also made back then, I can take a look.

Just to look at how presure and flow relate with a typical electric pump, here's a couple graphs from the 2014 Holley catalog.
View attachment 1715382125

It is a Mallory 4309 It is designed for a boosted application.

 

[Mattax]

I was thinking 'bout the pumps but that's fine.
Here's what they have on the 4309 regulator in this catalog.
Also the promo/tech on their regulators from the inside back cover.
Under that are a couple of pump delivery graphs also from the inside back cover.

Vertical axis is % of free flow. This is an in-line restricting type, not a return type.

 

[Cudafever]

Thanks.
I couldn't fine that part # anywheres. Do you know what that part # up dates to and is there a rebuild kit for it?

 

[Mattax]

Thanks.
I couldn't fine that part # anywheres. Do you know what that part # up dates to and is there a rebuild kit for it?

Yes. See if FABO doesn't shrink it too much.

Not sure how to attach it so you can click to see the original.

Here's a cropped shot

 

[flyfish]

That's funny that Mallory's propaganda says that their regulator is soooo much better than the Holley.....yet the diagram shows that they are the same on the inside, lol.

 

[Cudafever]

Ok here is the skinny!
Regulator at 9 psi, flow restricted too..........
6.5 psi =55 sec (Per gal)
7.0 psi=1:03 or 63 sec
7.5 psi=1:40 or 100 sec

 

[Mattax]

That's funny that Mallory's propaganda says that their regulator is soooo much better than the Holley.....yet the diagram shows that they are the same on the inside, lol.

I think the ball seat regulator is a deadhead type. Goes in line with the flow.
And it works something like this.
When pressure on the ball and diaphragm is low, fuel flows past the ball.

As pressure in the regulator rises, the diaphram moves up allowing the ball to seat.

With the Bypass regulator, I think it works like this.
As long as pressure is low, fuel goes straight through.
As pressure against the diaphram rises, the return valve opens; and the stem may also partially block straight through flow.

 

[flyfish]

Ah, Gotcha, at a glance they look very similar.

 

[Mattax]

This is the pump i'm running.
Walbro High-Pressure Inline Fuel Pumps GSL392BX

Here's what I found on-line for that pump.

That says to me that if the pump outlet sees about 9 psi, running on battery it will move over 70 gallons per hour.
Here's an instruction sheet for the regulator (which Holley has given a new number but the Instruction sheet still has the old one; 4309. )
https://www.jegs.com/InstallationInstructions/600/650/650-4309.pdf

And if I understand correctly, then the Cudafever car is plumbed like this.

When the bowls are filled high enough so the floats can keep the inlet valves shut against 9 psi,
the fuel flow into the regulator equals the flow returned to the tank (70 gph to 80 gph).

When fuel in the bowls is lower, then pressure at the inlet must be lower.
The more open the needle valves, the lower the pressure.

Pressure fully open is not known, but its above zero.

Ok here is the skinny!
Regulator at 9 psi, flow restricted too..........
6.5 psi =55 sec (Per gal)
7.0 psi=1:03 or 63 sec
7.5 psi=1:40 or 100 sec

Putting the first test result on the diagram shows this.

and with the inlet valve open less so its at 7.5 psi

 

[Mattax]

Love to see you do this:

Set the regulator to 6.5psi, set the ball valve for 5.5 and 6.0psi(test both), and see if it’s still in the 50 second range per gallon.

That would represent the carb inlets just somewhat open but the regulator set lower. Should be easier on the carb's inlet system to control and have less turbulence and aeration.
Then you could try with the ball valve set at 4 psi, which would be the same pressure drop between the regulator and the carb as in last night's test (9 psi to 6.5 psi).

 

[Mattax]

Here's a consumption estimate for engine that peaks at 450 hp at 6500 rpm:
Just give you some idea of what the delivery look like vs Hp, which of course is rpm related.
RPM HP Fuel Use in Gal/Hr
5000 375 31
5500 400 33
6000 425 35
6500 450 37

 

[Cudafever]

Love to see you do this:


That would represent the carb inlets just somewhat open but the regulator set lower. Should be easier on the carb's inlet system to control and have less turbulence and aeration.
Then you could try with the ball valve set at 4 psi, which would be the same pressure drop between the regulator and the carb as in last night's test (9 psi to 6.5 psi).

I don't see how this would teach us anything......A what the hell it's still hooked up. be back

6.5 regulated
5.5 psi 60 sec per gal
6.0 psi 65 sec
could not believe it so i checked it twice.

Well there you go...................

Edit didn't to the 4 psi sorry
i need to get my new metering blocks in as the race is Saturday and i'm not ready.
analize a way.
I will be back later

 

[Mattax]

Close enough. @PRH What do you think?
My takeaway is setting the regulator at 6.5 psi will supply more fuel into the bowl with less float drop.

 

[Cudafever]

and i check it twice
with the same results.

 

[PRH]

6.5 regulated
5.5 psi 60 sec per gal
6.0 psi 65 sec

I suspected there would be less pressure drop with the system pressure set lower.
So, it looks like there would be less than 1/2 a pound differencial between the set pressure of 6.5psi vs the max consumption flow of about 1 gallon in 85 seconds.
That’s how I like to see it, so I’d leave it set like that.

I not too optimistic this will solve the laying over problem, but at least we have a good handle on the system capabilities, and know it’s up to the task of CF’s requirements.

 

[Mattax]

Probably will have to reset the float adjusters to get the same fuel level in the bowls with 6.5 instead of 9 psi.
Just a reminder to check after firing it up.

 

[mderoy340]

I would be more concerned with how much fuel flows in 12 seconds @6psi thru 2 .110 orifices.

 

[Cudafever]

Ok so here is the precursor.
Installed Proform metering block with same jets and jet extension in the rear.
As i'm starting to buy in to the change in P.V set up, i pull my 4.5 and put my 6.5 P.V. back in.........had a 10.5 but not tempted to us that on just yet
When back and forth about the regulated pressure. altho i have been convinced that 6psi is better then 9........I set it at 9 to see how my metering block will act, compared to the Demon one's.
will make a couple laps and then drop it to 6 and probably just run it that way the rest of the day. sure i will have to raise the float, once i do this.

Started, set floats, warmed and tested........"Garage Nationals" say it's not bogging.........we will see........

In neutral revving the eng up slowly to 4000 rpm, it seam much cleaner...........Idles better, even in gear......

Fuel mixture screws are only 1/4 of a turn out for the best vacuum, which is the same as with the demon metering block.

Way to late to test it any more. loaded it on the trailer,... Going Racing Tomorrow!!!!! If i don't get called out. FINGERS CROSSED!
I'm hopeful but not holding my breath. If it don't work i will load it up on the trailer and do some testing next weekend when im not on call.

Wish me luck!!!

 

[Cudafever]

I suspected there would be less pressure drop with the system pressure set lower.
So, it looks like there would be less than 1/2 a pound differential between the set pressure of 6.5psi vs the max consumption flow of about 1 gallon in 85 seconds.
That’s how I like to see it, so I’d leave it set like that.

I not too optimistic this will solve the laying over problem, but at least we have a good handle on the system capabilities, and know it’s up to the task of CF’s requirements.

Holley says 9 psi is the max that should be run. So that is what i have been running thinking it was the fastest way to keep the bowl full. Any you could never convinced me otherwise, had i not gone through all of these test.
Glad that i did these test. A Real Eye Opener. Never thought about turbulence in the fuel bowl with Higher pressure and never ever would have believed that lower pressure equals more steady flow.

We got a little frustrated with each other(because i Knew you were wrong) but i'm glad i did the test to find the Truth...........OK ok, that you were right!

 

[yellow rose]

Ok so here is the precursor.
Installed Proform metering block with same jets and jet extension in the rear.
As i'm starting to buy in to the change in P.V set up, i pull my 4.5 and put my 6.5 P.V. back in.........had a 10.5 but not tempted to us that on just yet
When back and forth about the regulated pressure. altho i have been convinced that 6psi is better then 9........I set it at 9 to see how my metering block will act, compared to the Demon one's.
will make a couple laps and then drop it to 6 and probably just run it that way the rest of the day. sure i will have to raise the float, once i do this.

Started, set floats, warmed and tested........"Garage Nationals" say it's not bogging.........we will see........

In neutral revving the eng up slowly to 4000 rpm, it seam much cleaner...........Idles better, even in gear......

Fuel mixture screws are only 1/4 of a turn out for the best vacuum, which is the same as with the demon metering block.

Way to late to test it any more. loaded it on the trailer,... Going Racing Tomorrow!!!!! If i don't get called out. FINGERS CROSSED!
I'm hopeful but not holding my breath. If it don't work i will load it up on the trailer and do some testing next weekend when im not on call.

Wish me luck!!!

If you are only a 1/4 turn out on the mixture screws you can make the idle feed restricters .002-.004 smaller. Damn am I thinking correctly??

Yes, take a little fuel out, or make the idle air bleed a few thou bigger.

 

[Cudafever]

Hmmmm my have to think about that.........




OK so for those that like it short and to the point here it is
took three runs to dial in the carb, no bog no popping and banging on the top end. O and i got this!

 

[Cudafever]

Ok for those that need/want more info here it is.

first run was with req at 9 psi launched hard with no sign of stumble or sound of possible stumble. Top of 2nt gear it popped. shift into third and it came back around 4500 rpm lifted before the finish line 70 mph and a 8.18 et with a 60 foot of 1.748

So i dropped the fuel pressure down to 6.5 psi. Didn't affect the fuel bowls much so i left them alone, and made another run. At the finish line it started to pop and bang 85.5 mph, 8.00 et and a 1.752.
So took my sunglasses off and put my reading glasses on and set both bowls dead nuts center in the bowl. had to raise both up a little with the front needing the most adjustment.
No bog no pop or bang and i ran it past the finish like to hit my shift light in 3d gear, NOPE no bang!!!!. Worked great and did so the rest of the day. 86.3 mph, 7.89, and a 1.736.

As you can see above i made the next 6 round of racing, got the win in the finals. I dialed a 7.83 cut a .006 light and ran a 7.819. He dialed a 7.35 and ran a 7.30. and my 60 foot time was a 1.694.(only twice have i 60 footed in the 1.6's)

My best time is a [email protected] and that was in 7900 foot air. today the best was 8937 and most of the day was 90XX to 9391 adj altitude.

Didn't have to do any big smokey burnout to make it stick, hooked all day long at 14.5 psi in the slicks.
took some Gopro of the suspension and some other fun and funny things but haven't downloaded and edited then... Maybe tomorrow.

Got called out to work about 3d round. But was able to talk the operator threw the problem so i didn't have to leave. Sure glad too!!!!

OK now for the Proform metering blocks. I just threw them on! didn't clean or check orifice sizes just threw them one.

It's a brass jet in the top but that one for the emulsions is a brass plug. So there is 4 small opening and one plugged. wasn't happy with this when looked at it...........But i'm fine with it now..

 

[yellow rose]

Ok for those that need/want more info here it is.

first run was with req at 9 psi launched hard with no sign of stumble or sound of possible stumble. Top of 2nt gear it popped. shift into third and it came back around 4500 rpm lifted before the finish line 70 mph and a 8.18 et with a 60 foot of 1.748

So i dropped the fuel pressure down to 6.5 psi. Didn't affect the fuel bowls much so i left them alone, and made another run. At the finish line it started to pop and bang 85.5 mph, 8.00 et and a 1.752.
So took my sunglasses off and put my reading glasses on and set both bowls dead nuts center in the bowl. had to raise both up a little with the front needing the most adjustment.
No bog no pop or bang and i ran it past the finish like to hit my shift light in 3d gear, NOPE no bang!!!!. Worked great and did so the rest of the day. 86.3 mph, 7.89, and a 1.736.

As you can see above i made the next 6 round of racing, got the win in the finals. I dialed a 7.83 cut a .006 light and ran a 7.819. He dialed a 7.35 and ran a 7.30. and my 60 foot time was a 1.694.(only twice have i 60 footed in the 1.6's)

My best time is a [email protected] and that was in 7900 foot air. today the best was 8937 and most of the day was 90XX to 9391 adj altitude.

Didn't have to do any big smokey burnout to make it stick, hooked all day long at 14.5 psi in the slicks.
took some Gopro of the suspension and some other fun and funny things but haven't downloaded and edited then... Maybe tomorrow.

Got called out to work about 3d round. But was able to talk the operator threw the problem so i didn't have to leave. Sure glad too!!!!

OK now for the Proform metering blocks. I just threw them on! didn't clean or check orifice sizes just threw them one.

It's a brass jet in the top but that one for the emulsions is a brass plug. So there is 4 small opening and one plugged. wasn't happy with this when looked at it...........But i'm fine with it now..

View attachment 1715384090

So just a few touch up things and you'll be pooping in tall cotton. Nice job at the track!!!!!

 

[Mattax]

So took my sunglasses off and put my reading glasses on and set both bowls dead nuts center in the bowl. had to raise both up a little with the front needing the most adjustment.
No bog no pop or bang and i ran it past the finish like to hit my shift light in 3d gear, NOPE no bang!!!!. Worked great and did so the rest of the day. 86.3 mph, 7.89, and a 1.736.

Glad you were both dogged and methodical enough to work this through. Especially being willing to go back to the beginning. Not many folks like it when I say start with the fuel level. And in your case it meant going back to the delivery system.

Glad you were willing to test what @PRH was suggesting.

OK now for the Proform metering blocks. I just threw them on! didn't clean or check orifice sizes just threw them one

Now think how much better it will run when you make them right.
Just bustin on you. Glad they worked OOTB.
If you do decide to experiment with them, I'd start with the e-holes, and a logger or gopro on the AFR will help because that stuff happens quick. And if you don't want to experiment, that's cool too.