Holley/Demon Carb stumble

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'63GT said:
OH ! I guess I missed that.. you have a carb that works? (ProForm)
Who has been doing your converters? 9 1/2"?
Click to expand...

kind like the Johnny Cash song "I built it one piece at a time". In the end i had two carbs.
So i put the Demon back together to see if i was going to keep it as a spare or sell it..........still haven't decided that.
 
He is very competent ! normally an 8" guy though.. Yours a 9" or 10"
 
9 Inch i think, we talked about a 8 inch but he talked me out of it.
its not a 10. 9 or 9-1/2
 
The 9 1/2 offers a lot of unique capabilities..
 
I when from 8.10- 8.20 and 95 96 mph
To a best of 7.78 1.5 mph faster and 200 less rpm at the 1/8 finish line.
I am not unhappy with my TQ....just my Demon carb that keep complaining.:D
 
Good ! looks like you've been taking bites out of the clock ! that's always fun :)

To be fair... your car would be a different animal at sea level.. that converter too.
It's not uncommon for a class racer to have an 'altitude' converter for that reason.

Did Lenny know about your altitude ?
 
Yup happy with the combo but never satisfied
At see level i would probably pop a head gasket.
12.8 compression and a custom cam spec for this High altitude.
 
:thumbsup:
Great chattin with ya! got to hit the hay, before I turn into pumpkin lol
 
Cudafever said:
9 Inch i think, we talked about a 8 inch but he talked me out of it.
its not a 10. 9 or 9-1/2
Click to expand...


Thats weird because a few months back I ordered a converter for a street/strip 56 chevy truck and it came down to a 9 inch case and an 8 inch stator or an 8 inch case with an 8 inch stator.

We ended up going 8/8 and it’s amazing how it works. It’s a PTC and it’s their Drag Week converter. And that was picked because it’s 80/20 street.
 
Cudafever said:
I when from 8.10- 8.20 and 95 96 mph
To a best of 7.78 1.5 mph faster and 200 less rpm at the 1/8 finish line.
I am not unhappy with my TQ....just my Demon carb that keep complaining.:D
Click to expand...

It" not that the TQ is to tight, it's that the Demon is just to big, so big that i can't over come it with the combo i have.
Still plan on a ET Slip or two on this Demon carb before i pull it off. As well as some Gopro/ o2 run readings.
Then put the Proform back on and do the same test.
 
OK HERE WE GO!!!!!!
Mitty Demon 850 ET slips,
850 Proform carb ET slips,
Same day, Same air, Same launch.............How will they stack up.................
Final comparison

Only thing different is that the Demon got 6.5 PV, Removed for a 10.5 PV..........will it make any difference in the stumble???........ Probably not.
Hope to get lots of answer tomorrow..........Or at least good data
First 2 run will be a long High gear pull. hoping i can get the gopro to capture some O2 reading pulling thru top gear, with both carbs.

Will be starting out the day with a vacuum gauge tape to my windshield
Several runs with the Demon, then run the Proform the rest of the day.
 
Cudafever said:
Its a 850 double pumper carb running on a 12.8:1 compression HYd roller cam 408.
4200 stall and 4.56 gears out back.

Now this stumble started show it ugly head the first of this year. And Every Holley book and YOUtube i have watched say if it stumble at the first of the full throttle stomp. YOU NEED BIGGER SQUIRTERS.
I started out with what can in the carb, which is 31's, then 33 and seamed to fix the problem......
next race had the same stumble problem so i when to a 35 and stumble when a way............
Last race had same problem and when to a 37. problem solved and ran good again. Vary confused but fix the problem so well ok.................

So today i install my 90/10 shock up front and put my GoPro back under the car to see how the 90/10 work.
Guess what!!! Yup the stumble is BACK.
Now one more tidbit before you watch the video. I made sure there was 0 play between the squirter arm and lever. secondary need a slight adj and figured it was going to run even better. But NOOOO

With all of this i don't' think the Squirter is the problem, but what is?????

You can watch the hole video but the "drive and stumble" is about 1.30 into the video
If i roll the throttle in it works just fine. but if i stab it, it stumbles........

Click to expand...

I would think perhaps the fuel level has changed in the float bowl?
Can’t imagine it getting leaner however
 
Cudafever said:
OK HERE WE GO!!!!!!
Mitty Demon 850 ET slips,
850 Proform carb ET slips,
Same day, Same air, Same launch.............How will they stack up.................
Final comparison

Only thing different is that the Demon got 6.5 PV, Removed for a 10.5 PV..........will it make any difference in the stumble???........ Probably not.
Hope to get lots of answer tomorrow..........Or at least good data
First 2 run will be a long High gear pull. hoping i can get the gopro to capture some O2 reading pulling thru top gear, with both carbs.

Will be starting out the day with a vacuum gauge tape to my windshield
Several runs with the Demon, then run the Proform the rest of the day.
Click to expand...
Perhaps a vacuum leak, enriching the squirter has been covering for?
 
BRING ALL THE IMPORTANT STUFF UP TO THE PRESENT PAGE
Expand and watch video V V V V V V V V V V
Cudafever said:
First of let get up to date.
This is my Mighty Demon Carburetor. All the part i put on this one to fix the problem i ended up with another carb. and was able to put this one back together.

Tell me what you think of the video. i was able to get closer and a better, Clearer video of the carb/fuel flow
after the slow mo,(EDIT: the slo mo is in high gear) all the rest are with it in high gear, foot on the brake.
THE SLOW MO WAS IN GEAR FULL THROTTLE

2nd video is only me raising RPM up to what i'm at staged and ready to good and what vac the eng has at that point.

With all that, look at it and tell me what you think
Woop!
I uploaded the UN edited version.:realcrazy: O well here you go.



Click to expand...


'63GT said:
Look at that ! the 2:30 slow mo shows it. No fuel flow at the boosters = bog
Reduce the HSB 2 sizes and try it again :)
(qualifier: that 850 is probably too big and signal drops to nearly nothing.. exasperating the isssue)
Click to expand...
:thumbsup:
Cudafever said:
Thought i would give you all a day to tell me what you saw before i went and did the same.
First off....Yup, like has been said and implied all threw this thread, the Speed Demon 850 is JUST TO BIG!
And watching the booster trying to draw fuel and only being able to dribble is "dead truth!"

But this is what i notices beside from the bad Shake, dim lit video.

At the beginning of this thread when i keep throwing bigger squirted in it to fix the bog and every on said Put A 50cc pump in it. I never could decide if i should put it in the primary side or the secondary side.!? Well that video showed the primary side squirt er die out much sooner then the secondary.
NOTE: 50 cc on primary side.

I noticed that the left/drivers side Rear Venturi would dribble a little when i open up the secondary, manual.

In the slow mo video, even when the mains came on, they were more drippy then spraying.
Primary never did more then drip.

Why does it bog/act up, MORE when it warm then when i have run it for a while at eng temp??????
MY Answer: when the fuel come out of the mains in a dribble,(droplets) the bottom of the manifold is hot enough to put it into suspension...or more of the droplet into vapor.

My Cruise rpm is steady state around 12" of vac and 9 under slight acceleration.
My staging rpm is around 9" and i have a 6.5 PV in it right now.
Would replacing my 6.5 for 10.5 PV help????? Probably but not enough. The full throttle dribble would still be the same as we r at (0) vac at that point.

As far is the o2 meter. that is as much live data so far.
that was from about 20 mph in 3d gear 4000 stall up to 5000 rpm.
Ran out of road to go to 5800 rpm
Like the fact that it leaned down to around 12.6 then when back up to 13.5 and look like it was going to hold around there.
Note: only full throttle, is accurate numbers as the sensor is a foot from the exit of the exhaust


"Whats next?"
Well i want a ET slip with a good mph from this carburetor, then pull it off and start to figure out why the Proform don't pull as well on the top.............or that my butt odometer is incorrect and there is no different in the top rpm/ HP between carburetors.(same day same air)
Was going to have a T@T this week end but Mother Nature say NO!!!!
Click to expand...

Houseoffubar said:
I would think perhaps the fuel level has changed in the float bowl?
Can’t imagine it getting leaner however
Click to expand...
FLOATS ARE ACTUALLY SLIGHTLY HIGH IN THE BIG DEMON SITE GLASS

Houseoffubar said:
Perhaps a vacuum leak, enriching the squirter has been covering for?
Click to expand...
NO VAC LEAKS, AND NO BRAKE BOOST TO COMPLICATE THING EITHER.

I'm exited, think this will be a vary interesting day..............a day that need to happen long ago.
 
Well grate intentions but not grate results.
Had the largest crowd ever. We had So many that the street tire cars had to park on the grass.
So my intention of getting 4 or 5 test runs on each carb......Well that when out the window.

I'm beat and will type more tomorrow but the high lights is that the Mitty Demon MPH the same and the Proform. 86.4 to 86.7 esh on both carbs. So the Demon didn't mph better then the Proform
Demon only got two test runs before i pulled it off and installed the Proform.
Also the Adj Air density stayed in the mid 8500 foot range all day, so was a grate day to compare these two carbs

Just a small Teaser for tomorrow.
We built a sand trap and catch net at the end of or track.........and i was 10 feet from being the first to test it out!!!!!!!:wtf::BangHead::realcrazy:
 
Ok so the video is dark when i'm trying to get the car shut down, but you will get it.
Only had 2 run with the Demon. the 2nt one, i just tried to make a normal run and then grab the gopro to show the o2 reading in high gear.....Fail!!!!

It's kind a funny, what you think you can do in your minds eye..........you just can't do that fast.
Just before my first test run i practiced what i was going to do with my gopro.......didn't happen and all most found the sand trap...
Any hoo, this video is on the runs with the Mitty Demon and the proform will be on the next video

 
OK
so you can't see the ets here they are'
first run
1.925 60 foot
8.289
84.07
2nt run
2.044
8.207
86.64
 
Hay Jpar FIND SOME OTHER THREAD TO PICK A FIGHT IN.
WITH 318 OR ANY ONE ELSE.

318 6600 foot elevation.
 
Is that the way to treat the only person that responded to your carburetor tuning career...
 
These are the ET slip with the proform.
will add dialog latter.
IMG_0125 (1).jpg
IMG_0126 (1).jpg
IMG_0127.jpg

Proform 60' a lot better.
 
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