Holley/Demon Carb stumble

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LOL Reaction times Sucked.......Less....... with the proform.
My 1.767 60' run, I was told by a friend that i had pack the front wheel!
Handed him my gopro and say PROVE IT! He was unable to do so.:(
 
Cudafever said:
LOL Reaction times Sucked.......Less....... with the proform.
My 1.767 60' run, I was told by a friend that i had pack the front wheel!
Handed him my gopro and say PROVE IT! He was unable to do so.:(
Click to expand...
Well I was thankful to see they got better from the first time slip you showed...
when I seen the first time slip all I could think was hey wake up it's time to go LOL... But the last one .014 that's ok...:thumbsup:...
 
j par said:
Well I was thankful to see they got better from the first time slip you showed...
when I seen the first time slip all I could think was hey wake up it's time to go LOL... But the last one .014 that's ok...:thumbsup:...
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Lol that was not mine. That was the reaction of the dragster. All my runs were in the Left lane.
 
Cudafever said:
LOL Reaction times Sucked.......Less....... with the proform.
My 1.767 60' run, I was told by a friend that i had pack the front wheel!
Handed him my gopro and say PROVE IT! He was unable to do so.:(
Click to expand...
with the car shading the wheel you can't see it. BUT in the slo mo you can see the front Wheel slow just for a moment.
 
So i'm done with the Mitty Demon.
It's a good usable carb now and i probably could make it work with a 50cc squinter pump but the proform will 60' all most 2 tenths better........The carb is off and will stay off until i build a bigger motor and decide to twist it 7500 rpm(no money for any of this)
The only thing that was not apples to apples comparison was that the Demon was jetted up 3 size bigger then what i was running it before. Trying to help with the stumble along with a change of power valve from 6.5 to a 10.5.
first on is the best run on Saturday
IMG_0128.jpg
with the Demon and the 2nt on is the best run with the Proform.
IMG_0129 (1).jpg

all runs were in the left lane
 
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Can you post a couple of pictures of your spark plugs? Not all of them, just one from each bank. And if you can, take the shell off one of them so you can see the fuel ring.

I’m not sure if you posted what you have for a high speed air bleed, but if it’s too big it can delay the start of the booster enough you’ll get a hole in the fuel curve that you can’t cover up.

Also, since I can’t remember the details...did you install T slot restricters? What about the PVCR’S? Did you put brass in them so you can tune that circuit?

TIA
 
We all know pic are hard to read a plug. but i haven't pulled a plug in a while so i will do that.
think i still have one new plug so cutting off the threads of one should be now problem.

Explain to me again what "T slots do and where you install them and what it accomplishes.
 
Cudafever said:
We all know pic are hard to read a plug. but i haven't pulled a plug in a while so i will do that.
think i still have one new plug so cutting off the threads of one should be now problem.

Explain to me again what "T slots do and where you install them and what it accomplishes.
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The T slot is where you get fuel when you transition (or transfer) from getting fuel from the curb discharge port and getting on the booster/main jet.

After this weekend I’m going to start doing more 1:1 linkage carbs again. It keeps you on the transfer slots longer. And they just drive better.

They are installed in the main body where the metering block bolts on.
 
Ok i was thinking that it was some screw you drilled in to the transfer slot in the bore. You know the the one you set square in the bore with the butterfly
also no drilled and tap for the PVCR
Pic on the way but one question
how does restricting the transfer slot help make the booster come on sooner or transfer hold on longer.
 
Here you go.
Just a reminder the demon only had two run on Saturday the last 4 of the day was with my proform.
The plug on the left was put in at the end of last season. The plug on the right (right side #2 plug) is vary old.
the one on the left is cyl #1 and is the one that i cut the thread off of.

If i had realized it was so ease to hacksaw of the thread i would have been doing this long ago.
IMG_0141.jpg
IMG_0142.jpg
IMG_0145.jpg
 
IMG_0146.jpg
IMG_0146.jpg
I also did a video with my phone. don't know if i can make it work.
But if not, here is a couple more pics
To big of a file so i updated to YouTube

Removed video, so you didn't have to here me say bad words LOL
But mostly because it was blurry even in full screen. pics are better.
 
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so i was able to come up with a couple new plugs
so i cut the other one up as well.
left is #1 and right is cyl 2
 
Cudafever said:
Ok i was thinking that it was some screw you drilled in to the transfer slot in the bore. You know the the one you set square in the bore with the butterfly
also no drilled and tap for the PVCR
Pic on the way but one question
how does restricting the transfer slot help make the booster come on sooner or transfer hold on longer.
Click to expand...


It doesn’t. I was saying opening the primaries and secondaries 1:1 will keep it on the transfer slots longer. I’ll see if I can find a picture of where the T slot restricters go. I use 10-32 brass set screws for those. You can get away with 8-32 but you may not be able to get the hole big enough.
 
Cudafever said:
View attachment 1715549730 View attachment 1715549731 I also did a video with my phone. don't know if i can make it work.
But if not, here is a couple more pics
To big of a file so i updated to YouTube

Removed video, so you didn't have to here me say bad words LOL
But mostly because it was blurry even in full screen. pics are better.
Click to expand...


Put the video back up!!!! Bad words don’t scare me!!
 
Cudafever said:
View attachment 1715549771 View attachment 1715549772
so i was able to come up with a couple new plugs
so i cut the other one up as well.
left is #1 and right is cyl 2
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You are still rich everywhere. I look at the porcelain in thirds. The top third (this is a very loose measure...sometimes it’s not quite equal thirds...so the more you cut apart plugs the more you’ll learn to discern what you are looking at more accurately) is idle and just off idle. You can get screwed up looking at this part of the plug if you are a throttle blipped or you have relatively big squirters or worse...both. The pump shot can make that part of the plug look fat when it’s not. It’s the throttle blippers that feel the need to whack the throttle 6, 7, 10 times to “clean it out” when in reality they are dumping a crap load of fuel into the engine.

The middle third is T slot and cruise which depending on gearing and tire size can also be on the main jet, and most likely will be showing both T slot and main jet. Learning how to tell what you’re looking at takes time and reading as many plugs as you can, and just looking at them close and observing what it’s telling you. Also, there are some great plug reading articles out there, so reading them is a big help. I read them often so I don’t get set in my ways of looking at plugs, because when you do, you can fool yourself.

The bottom third (or a bit less in many cases) is WOT. If you are picking the fly poop out of the pepper, you can get the fuel ring down to .080-.100 wide. And none of this is set in stone either. If you keep trimming the fuel ring at WOT down and the car looses MPH, then you need to give it what it wants, to a point. If your car has a higher MPH with a wider fuel ring, then give it to it, unless it’s as wide as yours. That has to be about .250 wide or more and that is just too wide. If it’s faster with that tune, something else is wrong.
 
Cudafever said:
Ok you can get a laugh out of it but the video Q Sucks!
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That is classic! I love it, but what came up next was unreal. I’ve never seen the video of demon carb doing that.

What I do know is I had a Holley carb that did the exact same thing. I never fixed it, and no one else would (or could) either. When I called with the list number every carb guy in the country said just get a new carb. That happened to be an annular discharge. That damn thing had an 850 venturi and 1.688 throttle blade, which is *** backwards. It had a giant hole in the fuel curve just like that.

That carb was bought by my brother back in 1988ish and was used on several different combinations and it was always the same. I could never figure it out and never found anyone who was willing to try and fix it.
 
A carb configured like the 850MD, 1.560v x 1.750, downleg booster, DP, can be a challenge to get to leave hard....... even when it’s the right size for the motor combo it’s sitting on.
Which in this case...... it’s def not.
Add in the 8000’ DA and it just gets worse.

Watching the vids of it on the motor, looking down the carb during the attempts at winging the throttle and seeing it’s not anywhere even remotely close to working as well as it would have to, to get good launches by footbraking.......it’s time to accept that no matter how much you mess with it....... it’s not going to work as well as something that’s just a better match for the overall combo.

If you’re having a good time messing around with it, that’s fine.
The fact that there’s .2+ gain in the 60’ by swapping to another carb tells the tale.
On that combo, at that elevation...... it’s the wrong carb.
 
That damn thing had an 850 venturi and 1.688 throttle blade.
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Holley 9381.

At some point, the 1.560 x 1.688 configuration became the NASCAR standard sizing.

The Street HP 850 also uses that sizing.

Not a fan.
 
PRH said:
Holley 9381.

At some point, the 1.560 x 1.688 configuration became the NASCAR standard sizing.

The Street HP 850 also uses that sizing.

Not a fan.
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Thank you, that’s the one.

BTW...any chance an annual booster would help that demon? It dang sure didn’t help the 9381.
 
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