Holley/Demon Carb stumble

[Cudafever]

But, when do you "cruise" a Drag Car????
I have sence learned the PV has nothing to do with idle........unless you have blown diaphragm on it. two separate circuit.

Thanks by the way......just couldn't pass up being a smart arrs

 

[yellow rose]

But, when do you "cruise" a Drag Car????
I have sence learned the PV has nothing to do with idle........unless you have blown diaphragm on it. two separate circuit.

Thanks by the way......just couldn't pass up being a smart arrs

LOL. You are correct. You don't cruise a drag car. If you are going to run a PV and if you are foot braking it, a PV that opens quicker makes the transition cleaner.

Transbrake and a two step and maybe you just eliminate the PV, but even driving back to the pits can dirty the plugs up a bit.

 

[Cudafever]

So got my ProForm main body several day ago and and when to putting it together tonight.......I guess it's actually morning now.
so here is a picture of the two main bodys together. Both clam to be a 850. wow what a difference!!!

I didn't fine any differences, one from the other as far as passages go. but i think i found some of my problem that i have removed and clean and scraped with a pick to make sure.

This is what i found in both fuel transfer slots on the secondary side. and then i found a bur/ thread in the bottom of one of the main jets in the valve body. took a little time with a pick to bend/ and brake it off. and then made sure it landed in my hand when i turned it upside down. Needles to say, I when threw 2 full cans of carb spray on this main body swap.

Start and test it out tomorrow. Cross your finger for me...............

 

[skrews]

You get the carb up and running?

 

[Cudafever]

yes and no.
Its together and i took it for a stomp. that's when the o2 gauge took a crap.
It didn't stumble and it didn't hook but then it stumbled after the 1-2 shift. idled it back and check the float bowls and haven't started it sence.
When with the stock jets that came with the main body and also didn't change the main bleed as you had suggested.
was hoping to get a baseline, with my o2 gauge, and then play with them. But that failed.

I have got to go back out to the track in the morning, hope to play with it tomorrow night.
The main/secondary jets are to large for sure(sea level jets)
how far down would you suggest i get them down(Main/secondary jets) or do you think i should be messing with the air bleeds or maybe squirters?

If i wack it to the floor, and then back it dies and takes opening the throttle to re start. if i bring it back up to a high idle afterwards i can keep it running.

 

[skrews]

I'd go down 4 jets at the most without confirming the AFR with the wideband. You might try a 36 hi speed air bleed and see what it does, if it hates it try a 28. Basically up 4 sizes or down 4 sizes.

 

[Cudafever]

What am i expecting to happen when i change the high speed jets
describe hates

 

[skrews]

See if it changes your hacks/stumbles. I don't think it will but its worth trying. The HS bleeds change the fuel curve. A larger bleed will generally lean out the higher RPM range and a smaller bleed will fatten it up. They can also change the sensitivity of the main circuit to tuning changes. Bottom line make a change, if the drive-ability gets worse make a step in the other direction.

 

[Cudafever]

K Thanks.

 

[yellow rose]

See if it changes your hacks/stumbles. I don't think it will but its worth trying. The HS bleeds change the fuel curve. A larger bleed will generally lean out the higher RPM range and a smaller bleed will fatten it up. They can also change the sensitivity of the main circuit to tuning changes. Bottom line make a change, if the drive-ability gets worse make a step in the other direction.

And the larger bleed will delay the start of the booster.

 

[Cudafever]

Got it together tonight, jetted down 4 front and back. Seem a lot snapy-r. Dark so hope to get home early(on time) so i can take it for a stomp tomorrow.
Saturday is coming up way to fast for me.

 

[Cudafever]

Well took it for a drive tonight.
launch stumble is gone!!!!!Yeah
but it start to break up on top end. float bowls are in the center of the Sight glass.
can't get my o2 meter to work properly to give me any help with the situation............

 

[Cudafever]

Would 14.1 be lean enough to pop and bang at full throttle?
It's hard to hold the o2 gage and shift the car so i did a 20 mph 3 gear stomp. when it starts to do the popping and banging the gauge read 14.1

 

[skrews]

Zipp tie that gauge to the dash or column lol, then go ring that sucker out through first and second gear to get some good feed back from the wideband.

 

[Cudafever]

Ok so i decide to put my 600 holley back on.
just to make sure it was a carb problem and not a coil going bad or some ign problem.
no popping and banging ran thru all three gears with a 02 reading in the mid 12's

So back home and installed 29 high speed bleeds (originals 33) and swapped back on the ProForm/Demon carb.
Darkness came upon me before i could test it. Sooo hope to get home on time tomorrow. So i can do a test stomp and load it on my trailer. So i can go racing on Saturday.

 

[mderoy340]

I suspect something is wrong with the metering blocks you ran with the demon/proform main body.
I run a Demon 750dp with 3 hole emulsion metering blocks. I tapped the holes and run .026 bleeds in all 3 with a .028 MAB This setup gives me a flat fuel curve all the way thru to WOT at sea level. Use the MAB to obtain a flat curve and jet to set AFR you want to run. If your blocks are stock the emulsion holes are .031. If you decide to tap, drill the .031 out to .052 and use a 6/32 tap to set the allen head brass set screws flush.
https://www.amazon.com/gp/product/B01N0KM570/?tag=fabo03-20
You also need to check the brass plugs on the top of the metering blocks. If they are leaking they are adding additional bleed air to the emulsion well and the carb will go leaner than you would expect. You can seal them with any good fuel resistant sealant.

 

[skrews]

Agree with above.

 

[Cudafever]

Take a look and tell me what you think.
this is the Demon/ProForm main body with MAB Drop down 4 number
It barked mid way thru 2nd gear. Now it's 5 grand in 3rd.
Tried to stay in it longer so maybe the o2 could show something........to violent! couldn't do it

 

[Cudafever]

So do i add more jet? or smaller Air bleeds.
Im leaning toward smaller air bleeds. MAB.

O and that was me lifting on the throttle to keep from roasting my slicks on pavement when i launched,

 

[skrews]

I'd take the AB down to 27s and up the jets 2 sizes.

 

[Cudafever]

K thanks
will do that and then load it on the trailer.
Test it at the track tomorrow.
Thanks again.

 

[skrews]

Take your other carb along.

 

[Cudafever]

Yup have tested the 600. Will get me threw this race if necessary.
Jetted up, smaller MAB, ran it long enough to load it on my trailer. fingers crossed.
pulled out a MAB out of the demon main body tonight...................Have no clue what size is in there. There even smaller than the ProForm air bleed. o well, i guess i just don't care about that part.

 

[skrews]

Let us know how it goes.

 

[Cudafever]

sure will.
getting excited now.
just gotta threw my go pro and air density meter. in the truck in the morning and i'm ready!.....I think.