Holley/Demon Carb stumble

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Cudafever said:
It easy to overlook and even easier to Assume.
So i had to go back out and pull the base plate back off.
Yup both holes drilled out on both side.

Good thought thow.
If it was only drilled out on one side........It could only go on one direction and work.
Click to expand...

Well....... you coulda just slid a small drill bit into the hole and made sure it went in pretty deep :p
 
PRH wrote
I don’t see any way that if both of those carbs were as sorted out as they could be...... that the PF bodied carb(with its smaller venturi) wouldn’t end up being the better choice for your application, especially at the elevation you race at.

After tweaking the calibration my 850 MD worked pretty well....... but I really only used it on motors making over 600hp.


Well it has been discussed...but not in this way.
How about a little bit more thought as to why you think the Demon would work better at elevation.
 
I rewrote that post, because I could tell it was going to be interpreted incorrectly.

If you take out the middle of the sentence it’s clearer......

“I don’t see any way that the PF bodied carb(with its smaller venturi) wouldn’t end up being the better choice”
 
Ok
I have heard people say that a bigger carb is better in HIgh elevation is better because the air has no ram aka air pressure.
Now i can jump on bored with both trends of thought.

I thought you were going down that road.

The hole reason i'm going down this road(besides not wanting a Demon spare parts box) is to see how it works. The Demon still has the best mph(but that was with 26 inch slick not the 28s i have on it now).
 
Cudafever said:
Ok
I have heard people say that a bigger carb is better in HIgh elevation is better because the air has no ram aka air pressure.
Now i can jump on bored with both trends of thought.

I thought you were going down that road.

The hole reason i'm going down this road(besides not wanting a Demon spare parts box) is to see how it works. The Demon still has the best mph(but that was with 26 inch slick not the 28s i have on it now).
Click to expand...
Maybe injecting some air...:D..
 
It takes air flow thru the venturi and booster to create a pressure differential to get the fuel flowing.
At elevation, the air is less dense, so it requires a larger volume of air to create the required differential.
The smaller venturi speeds the air up and makes it more dense, which helps activate the main circuit earlier........ which should make tuning the bog out easier.......which should make it 60’ better.
 
I know when I go visit my son in Colorado everything boggs! I mean every car I hear everywhere coming off of stop lights make a big bogging noise..
 
:eek::eek::eek:
That's a low altitude-r Trying to breath up here.:D
Like i have said before, it take a lot of work to make something N/A fast, up here.
 
My AFR recently started going full rich 10:1 after the motor was up to temp during highway cruise. Turns out the mechanical pump was percolating and the fuel bowls were low. I'm changing to an electric pump with a return line. The ethanol in the gas today sucks.
 
mderoy340 said:
My AFR recently started going full rich 10:1 after the motor was up to temp during highway cruise. Turns out the mechanical pump was percolating and the fuel bowls were low. I'm changing to an electric pump with a return line. The ethanol in the gas today sucks.
Click to expand...
Could be the winter fuel. But low in the bowls should have been a slightly leaner mix if anything. Do you have a fuel pressure gage you can mount on the cowl?

I have one but don't usually leave it on the car. its not waterproof (and draws extra attention that not always a good thing)
It sits in this location.
upload_2020-4-16_22-28-35.png

The steel tubing gets held under the black backet atteched tothe the washer nozzle screw.
Red strap hold s the gage to the cowl.
AN-line goes to a tee in the carb feed. AN cap when not using the gage.
 
Last edited:
Mattax said:
Could be the winter fuel. But low in the bowls should have been a slightly leaner mix if anything. Do you have a fuel pressure gage you can mount on the cowl?

I have one but don't usually leave it on the car. its not waterproof (and draws extra attention that not always a good thing)
It sits in this location.
View attachment 1715509616
The steel tubing gets held under the black backet atteched tothe the washer nozzle screw.
Red strap hold s the gage to the cowl.
AN-line goes to a tee in the carb feed. AN cap when not using the gage.
Click to expand...
I have a SW gauge reading zero under the hood. I'm installing a low pressure fuel switch 4 psi with the new system. Turned on the electric pusher pump and motor recovered. It happened at idle after a local drive and I was able to see the empty bowls, low fuel pressure, and crappy idle. In FL there is no winter blend that I'm aware of.
 
mderoy340 said:
In FL there is no winter blend that I'm aware of.
Click to expand...
Meh. Looks like there is. At least that's inferred here.
US EPA approves Florida, North Carolina requests to change summer gasoline RVP | S&P Global Platts
Not surprising. It's cheaper to make and sell making consumers happy and more profit.
Many states have their own requirements, some including 'drivability' requirements. Bet Fla is not one of them.
previous (2013) map here Date of switch to summer-grade gasoline approaches - Today in Energy - U.S. Energy Information Administration (EIA)

mderoy340 said:
I have a SW gauge reading zero under the hood. I'm installing a low pressure fuel switch 4 psi with the new system. Turned on the electric pusher pump and motor recovered. It happened at idle after a local drive and I was able to see the empty bowls, low fuel pressure, and crappy idle.
Click to expand...
Sounds like vapor lock on the suction side. Putting the line under pressure rather than suction should help alot.
When I've had that problem, it was also after idling and the worst was after stuck in traffic on interstate and a very warm spring day with winter blend.
I've added several layers of insulation and a shield to the lines back to the cross member. I also keep some 'storage fuel' on hand, which might happen to be in the gas tank when those conditions are present.

You prob won't need to do that with the pusher setup.
 
Mattax said:
Meh. Looks like there is. At least that's inferred here.
US EPA approves Florida, North Carolina requests to change summer gasoline RVP | S&P Global Platts
Not surprising. It's cheaper to make and sell making consumers happy and more profit.
Many states have their own requirements, some including 'drivability' requirements. Bet Fla is not one of them.
previous (2013) map here Date of switch to summer-grade gasoline approaches - Today in Energy - U.S. Energy Information Administration (EIA)


Sounds like vapor lock on the suction side. Putting the line under pressure rather than suction should help alot.
When I've had that problem, it was also after idling and the worst was after stuck in traffic on interstate and a very warm spring day with winter blend.
I've added several layers of insulation and a shield to the lines back to the cross member. I also keep some 'storage fuel' on hand, which might happen to be in the gas tank when those conditions are present.

You prob won't need to do that with the pusher setup.
Click to expand...
Thanks for the info on the fuel. I also insulated the lines under the hood.
 
Return fuel system back to the tank is the solution for vapor lock. electric or manual pump.
I had a little electric fuel pump that gave a pound or two to the machanical pump on the block.

When i went to a big electric pump with a return line off of the regulator. Vapor lock is a distant memory.
 
Cudafever said:
Return fuel system back to the tank is the solution for vapor lock. electric or manual pump.
I had a little electric fuel pump that gave a pound or two to the machanical pump on the block.

When i went to a big electric pump with a return line off of the regulator. Vapor lock is a distant memory.
Click to expand...
Vapor locked? What's that?..
You could get frostbite touching one of my carburetors...
 
Well the ProForm finaly got it fuel bowls today
IMG_2413.jpg
IMG_2414.jpg

Which allowed me to put my Demon carb back together...............

The Demon dwarphs the ProForm in appearance
IMG_2419.jpg


Is this how you make a Dual Quad work?:p

Work day at the track tomorrow, then Mothers day.................probably will be next week before i can test it out.
Solder the hole up in the butterflies, in the demon carb that were to large anyways.
If necessary, i will drill a much smaller hole back into them. we will have to see............

need to set float level and pump arms, air cleaner bolt and throttle bolts so i can put the throttle cable on.(complete carb so easy carb swaps)
Will do a street test on both carbs...........then get a ET from Both of them at the track on the 18th.
 
Cudafever said:
Well the ProForm finaly got it fuel bowls today
View attachment 1715524532 View attachment 1715524533
Which allowed me to put my Demon carb back together...............

The Demon dwarphs the ProForm in appearance
View attachment 1715524534

Is this how you make a Dual Quad work?:p

Work day at the track tomorrow, then Mothers day.................probably will be next week before i can test it out.
Solder the hole up in the butterflies, in the demon carb that were to large anyways.
If necessary, i will drill a much smaller hole back into them. we will have to see............

need to set float level and pump arms, air cleaner bolt and throttle bolts so i can put the throttle cable on.(complete carb so easy carb swaps)
Will do a street test on both carbs...........then get a ET from Both of them at the track on the 18th.
Click to expand...
I like that pro form
 
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