Street Demon 625 experience so far

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trebor75 said:
Alright. I will have it apart and take a closer look at it. I already had the nozzle of to see if it was plugged. Depressing the pump arm with my finger I can feel that it is spring loaded and it returns nicely. There is a needle under the nozzle, the pointy side should face down right?
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Yes
 
That is the check valve. I had one that was stuck in a holley and the darn thing would not squirt. Its just a gravity check valve. The acc pump plunger may be a double spring loaded affair: The linkage acts on a rod that pushes a spring that acts on the plunger that has another return spring under it. This style prevents the linkage from "hydro-locking" and bending in the event of a plugged squirter and it also allows the pump plunger to provide a controlled push when the throttle is blipped and the pump cannot discharge fast enough to keep up with the mechanical linkage. Holley has them on the end of their acc pump arm too. Your "pushing on the pump rod" may have just been the first spring rebounding, against a stationary piston.
 
So far I have 3 people interested in the carb & tuning kit for $150 plus postage. One of you PM'd me but I have not heard any response to my reply. Right now, I have to say first-come-first-served...
 
Had it apart today and I really could not find anything wrong with it. I cleaned it and put it back together and now I have a pump shot. I'm suspecting somethings up though. It's not squirting unless I really open up the throttle. Should it not squirt instantly? No play in linkage whatsoever, linkage is set for the biggest pump shot.
 
trebor75 said:
Had it apart today and I really could not find anything wrong with it. I cleaned it and put it back together and now I have a pump shot. I'm suspecting somethings up though. It's not squirting unless I really open up the throttle. Should it not squirt instantly? No play in linkage whatsoever, linkage is set for the biggest pump shot.
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Go to page 10 & 11 of these instructions. Your pump rod needs adjustment to the .25" dimwnsion shown. You'll need to bend the linkage.
http://documents.holley.com/lit701rev10.pdf
 
trebor75 said:
Yes I am sure. The wideband pegs super lean at the bog.
Geographic coordinates of Stockholm, Sweden
Latitude: 59°19′57″ N
Longitude: 18°03′53″ E
Elevation above sea level: 28 m = 91 ft
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Damn ,that's sweel cool good air....
 
Great video.. sure doesn't sound,like a 273.. Nice attention,to basics ,Trebor....
 
Thanks for sharing your experience, this was helpful as I dialed my SD 625. My engine is a 340, x-heads, stock compression, performer intake, mild cam, electronic ignition. Getting an AFR gauge revealed I was running too rich with factory settings, went "up" one size in both primary jet and rods and did a lot of playing with idle mixture screws. Now running 14's for AFR at idle and cruise, 12's for hard acceleration.
 
Had to make a comment.
This is an old thread, but I missed it last year, glad b5cuda brought it back. Now I'm interested in the Demons and TQ's. A lot of good info and trouble shooting from pishta.
And I love to read RRR remarks. Man He kills me! Take no prisoners! ILI
TREBOR75 was fortunate that MDEROY340 was available to help. He knows his Demons ! One of the best.
 
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I still run the Demon :) Now it's going on a 360 I'm building. I got sound advice and help in this thread! Have a good weekend!
 
trebor75 said:
Yes that sounds like something I should try asap. Before I went home from the garage today I leaned over the carb with a flashlight. I could not see any gas from the pump shot. I really made an effort but I could not get a visual of gas coming out of the accelerator pump nozzle when opening the throttle. The linkage has no play. I need to take a closer look at this. I'd be really surprised if there was something wrong with the pump because throttle response is amazing. Just weird that I could not see it.
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Did you adust (bend) the pump linkage as stated in the manual after changing to the different arm hole?
 
12many said:
Did you adust (bend) the pump linkage as stated in the manual after changing to the different arm hole?
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This is an old thread, the demon works great now. Yes, I did bend it.
 
This is what makes this a great site. Tons of information and helpful, knowledgeable people willing to take the time to help others.
 
trebor75 said:
I bought this carb about a year ago, brand new. Have not been doing much driving until lately though. This is my experience so far. Since it's a different design my old Moroso air cleaner hit the choke, so you either have to get a spacer to bring the air cleaner up a bit, or get the Street Demon air cleaner. The fast idle adjustment for the choke is accessed thru a hole in the back of the choke, facing the firewall. It's very hard to adjust without removing the carb.

Out of the box it has excellent part throttle response. The engine feels really happy and responsive. Easing into full throttle it pulls very hard. Great driveability so far! Returning to Idle it has some binding/sticking issue. I set it up to idle at 800rpm, I noticed it dropped to 600rpm sometimes. I removed my linkage and air cleaner and it's still there. This is after it has come of the fast idle cam. Pushing the linkage down with my fingers brought to it 600 rpm. I took the carb of to check the transfer slot and it was almost not visible. Set it to a square and opened and closed the throttle many times to get a feel and check for binding. It seemed alright but after installing it the problem remains. I have a fresh pair of return springs installed as manual suggest. So I need to take a closer look at this.

Driving it in a more spirited manner it has a bog when you stomp on it.
I borrowed my friends Innovate LM-1 wideband. The idle mixture was rich so I set it to around 14.7. That made it a bit leaner driving in low rpm's also. I get 12.5 on the highway at 2500 rpm. It has a bad lean bog going into WOT fast.

I don't have any jets or metering rods to swap as I just started tuning the carb. But I aim to lean it out a bit on the primarys. At WOT I got around 13, that's pretty good right? The Demon comes with 80 jets for the secondaries.

The secondaries have a air valve door to make the transition smooth. From manual: "The secondary air valve door is designed to dampen the transition from primary to secondary operation. Controlled by a torsion spring, the secondary air valve door is tunable to permit seamless primary to secondary throttle response regardless of the throttle rate opening. As an example, you experience a hesitation or backfire when the secondaries open. This means the secondary air door is opening to quickly, so it is necessary to adjust the door tighter (counterclockwise) until the hesitation disappears."

I've tuned this in small incremental steps to cure my lean bog going hard WOT. But the bog remains. So I moved the accelerator pump connection rod to the top position to give it larger pump shot. The bog remains. As I mentioned I dont have any jets, metering rods and accelerator pump nozzles to swap at this time.

I have a Pertronix Ignitor II & Flame Thrower coil. My initial is around 20-23. There is some lope in my cam so it's hard to say exactly. Total is locked to 36 and it's all in at around 2500 rpm. The motor seems happy, don't kick back, don't ping and don't get to hot.

I have checked float levels and they are spot on. I have checked the jets and nozzles for dirt.

So if I can get rid of the bog I will be a happy camper. Because I really like the throttle response of this Street Demon Carb. Compared to my Holley and Edelbrock I've had before this just feels much better for my combo. I'm not saying the other brands are bad in any way.

So I write this to get some tuning tips for the lean bog and just share my experience with the carb for anybody looking into getting one.

So this is my combo:
1970 Plymouth Duster
273 Commando - 1965
Compression: 10.5:1 (well this I dont know for sure, it's a true commando though).
Heads: Gasket matched and ported
Cam: Solid lifter Comp Cams Magnum 282S - 282/282 Lift 495/495 Beehive Springs
Edelbrock D4B intake / Street Demon 625 carb
PerTronix Ignitor II Billet distributer & Flame Thrower coil - Taylor plugwires
Hooker Headers
2.5" Dual Exhaust / Super 44 Flowmaster
727 auto / Shift Kit
10" Turbo Action Street "S-800" (17805SMED) converter (3200 stall)
8 3/4 - 3.55 - SureGrip
6 leaf - leaf springs from Espo
B&M Quicksilver Shifter
BF Goodrich 245/60-14 out back
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Did you ever get the binding/ idle problem fixed. My son bought a demon after his holley plugged up and everything seams to be fine except the idle. it idles fine on start up but as soon as you drive it and let off the gas it starts chugging really bad and wants to stall at stops. he is getting very frustrated.
his car has a slightly modified 318.
any help would be great.
 
trebor75 said:
Had it apart today and I really could not find anything wrong with it. I cleaned it and put it back together and now I have a pump shot. I'm suspecting somethings up though. It's not squirting unless I really open up the throttle. Should it not squirt instantly? No play in linkage whatsoever, linkage is set for the biggest pump shot.
Click to expand...

Exactly how is the linkage set? As many as I have built, I still get it backwards from time to time. The linkage should be in the hole nearest to the pump arm fulcrum for the biggest shot.
 
trebor75 said:
This is an old thread, the demon works great now. Yes, I did bend it.
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Well hot damn! It's more like a Thermoquad than I imagined, then, because linkage bending is common place adjustment with a TQ. That's pretty cool man. Glad you got it right. Are you happy with it now?
 
John Bare said:
Did you ever get the binding/ idle problem fixed. My son bought a demon after his holley plugged up and everything seams to be fine except the idle. it idles fine on start up but as soon as you drive it and let off the gas it starts chugging really bad and wants to stall at stops. he is getting very frustrated.
his car has a slightly modified 318.
any help would be great.
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Yes. I have had no problem since. Is it an electric choke on your sons Demon carb? I'm asking because it might be that the idle is to low when it comes of the fast idle adjustment screw. I oiled my wire from the pedal, aligned everything good and bought some new return springs. I also opened up full throttle and released it with my hand plenty of times on the carb. Cleaned everything on it too.

RustyRatRod said:
Exactly how is the linkage set? As many as I have built, I still get it backwards from time to time. The linkage should be in the hole nearest to the pump arm fulcrum for the biggest shot.
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Thats correct, the top hole is the one closest to the pump arm. It's kind of a funny angle.

RustyRatRod said:
Well hot damn! It's more like a Thermoquad than I imagined, then, because linkage bending is common place adjustment with a TQ. That's pretty cool man. Glad you got it right. Are you happy with it now?
Click to expand...
Just a little bend with my fingers worked fine. Yes, it has been really good on my 273 this summer. Great street carb for that engine.
 
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