I have a demon 750dp, and i need to convert the 30cc pump to 50cc on both the primaries and the secondaries. Can i just change the diaphram, or do i have to get the whole kit thing?

I looked for a kit from BG, but couldn't find one. The holley ones i have seen are all that gold color, which would look pretty silly on my silver Demon.

Any suggestions? part numbers would be great

Eric

 

The only kit I know of at this point is the Holley kit..and thats also according to Demon (real help guys!).Yeah I hear ya with the gold parts on the silver carb..but if it works I am OK with that.Does Demon make anything besides the carbs?!?!I am going to get the Holley kits this weekend for my Z (fingers crossed that it works).On another note..what power valve are you running?I went with a 8.5" or a 9.5"..can't remember now..have to look at my notes but that made a huge difference in the hesistation/flat spot.I get around 11" of vacuum at hot idle in neutral so I chose one that was around 2" below that according to Holley and Demon for a healthy street/strip motor.

 

i cant seem to run a power valve any higher than 6.5". i put a 7.5 in it and it wouldn't idle. I'm assuming it was open at idle. Vaccuum stays around 10-11 most the time.

Is there some sort of special technique for putting these power valves in? cause now that i think about it, mine wouldn't idle with the 6.5 or even the 4.5 without putting two of those little gaskets between the pv and the block.

Eric

 

No special technique i know of..I just install it.I use the gasket it comes with..just the one.Is there junk in the power valve cavity that holds it open when it gets tightened into place?Look for machining chips and flash when you have the carb apart.I have found quite a bit throughout the numerous times I have had my Demon apart..just a thought.

 

correction, i can't get any higher than a 7.5 pv. The 9.5 one i had in there caused the car not to idle, and my eyes to burn....

Eric

 

at idle with the 9.5pv did you try tightening the idle mixture screws to lean it up slightly?

are you absolutley sure theres no gas coming from the venturies?

 

Yea, the fuel should be coming from the idle feed when idling.
There's just not enough air velocity to draw the fuel out of the boosters when the throttle blades are closed.
So basicly the PV should'nt have any or no effect on the idle richness.
Make sure your block & bowl gaskets are properly installed on reassembly.
I use the Moroso buma gaskets, and they work very good.

If you can't adjust the idle richness via the idle screws then you have a different problem dealing with the primary blades being to far open at idle causing to much fuel to be drawn out of the idle feed. Still the PV shouldn't have any effect with this problem either.


>>>Again you guys are lucky!!! I only get 5 or so inches at idle.
High Alt + Over sized Carb + Big Cam + Single plane Intake = FLAT SPOT FROM HELL...Further reading makes me believe I will need to enrichen my idle circiut to cover it up, but I won't bore you guys with my situation

Ron

 

ronterry..are the idle air bleeds adjustable on your model Holley?I installed the tap in air bleeds included with my Demon and it cleened my idle right up.It is still a hair rich but WAY better than stock.

 

My idle is pretty good, but I have a part throttle lean spot while driving.
The PV are right on, but my vacuum is crap... Even Engine Analyzer software shows a predicted idle vacuum of 7.7" at sea level -- actual at 6300ft is currently about 5.5".
So I'm guessing either live with it (It's road race only car anywho) or go back to my dual plane intake orrr I could have an intermediate circuit installed on the carb...

BTW: Everything was ok till I went to a Victor Jr. Intake. (Again the Engine Analyzer states an idle vacuum of about 10.1" with my old Performer RPM -- actual at 6300ft was about 8" w/Performer RPM intake)

I really don't want to compromise on the Cam or carb, cause there just so matched. This combo would be awesome a sea level, but up here I need more air pressure to activate that main circuit sooner!
I even have annular boosters???

Ron

 

BTW: I just bought one of those Proform main bodies off of Summit, so well see if I can get a little bit more tune-ability at this altitude with my combo.
At the very least I think the bores are 1 3/8 with the Proform vs. my 1 9/16 830cfm, so this should help speed up the main circuit a little.
Smaller air bleed might help kick the mains in sooner?

Hey 'zupmanZ28' I saw this while browsing at Summit.

Summit Part # HLY-34-505 50 cc Chrome Accelerator Cover
Unfortunately it will tack another $13 bucks to the conversion.


Ron

 

Raising the float level is another way to speed up the activation of the main circuit also.Have you tried that just for the hell of it.A smaller air bleed also speeds activation up by raising the velocity in the air bleed via the smaller orifice.It worked wonders on my Demon.

 

I didn't know that about the float height, so I might mess with that.

I did bump my timing to 20° intial. The car just starts & idles so much better than the previous 16°...

I was looking at the air bleed kits. 170 bucks !!!! & back ordered to boot!!!
I might get some blanks, and drill my own on the drill press?

With all this super tuning, I might achieve 8MPG

Ron