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Trying to improve cold starts with a Demon 850

Kern Dog

Kern Dog

Life is full of turns. Build your car to handle.
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I have been having some rough running episodes when starting my car for the first time after a cool down. It runs lean, sputters and runs rough until it gets up to temperature. My air/fuel gauge shows it running between 16.0 and past 18.0 which is off the gauge's limits. Once it warms up, it settles into a 14.0 range.
There is no choke on this carburetor. There was when I bought it but in a moment of stupidity years ago, I pulled everything "choke related" off and tossed it. I have seen that many of the parts to retrofit an electric choke are available. What are the suggested Air/Fuel numbers for an engine at cold start? I'm currently looking for the parts to put it back together but for my own curiosity, the A/F target number would help.
Oh, if anyone has a dead 850 Demon that has all the choke parts intact, let me know!
 
On say 60 degree cold starts, you are looking for a 10-12 AFR. 18 is obviously lean enough to cause a stall.
 
I have strayed from that monster as much as I can.
Thanks again though!
 
It turns out that the choke kit listed above is out of stock and may have been discontinued. Son of a bitch..
 
Thank you. I just called, the man said it is not available. The search continues!
 
Talked to the holley rep he said they no longer have the parts an are not making them any more. He did tell me to look for a guy who bought out Barry Grant and has a ton of demon parts. Who you want to look for is Ninja Fuel Systems.

Here is the facebook info for Ninja fuel systems. may have what you need.
https://www.facebook.com/pages/category/Cars/Ninja-Fuel-Systems-104972756252025/

Here is the ebay store.
https://www.ebay.com/str/ninjafuelsystems

and last but not least his Email.
[email protected]
 
Holeeeee Crap. YOU are a helpful guy!
I have hit a brick wall elsewhere. 4 online sources and a local speed shop and everyone shows it being discontinued despite it being found in a search.
 
I have been unable to find these parts but the search continues.
I've tried emailing the Ninja guy. He never responded. I have been too busy working to step away and call Holley directly.
It is getting colder and I'd really like to get this done.
 
Boy 18 is really lean on a cold engine. Can't find a choke for your carb? I know, go EFI! (Just kidding).
Another consideration is the 800 CFM Edelbrock AVS2 with electric choke. I was just looking at them because Eddy had a 10% Halloween sale.
 
Thanks...
I just talked with a friend that owns one of the few carburetor rebuild shops in the Sacramento area. I didn't want to lean on him because he is really busy with his shop and a '70 Dart project that has been a pisser.
I might have him go through the carburetor since he has far more skill with them than I do. I can spray cleaner through everything but I don't know where most of the passages go.
Another thing: This cold start difficulty seems to be a recent thing. I bought this carburetor in 2003 or 2004 and the car has usually started up and ran okay after 30 seconds of fast idle without using any choke. I could start it, baby it for less than a minute and lift off the throttle and it would run fine. Over this past year, it runs really rough when I first start it. I have to run it for a couple of minutes before it is okay to idle on it's own. I filled the tank a year ago and have only ran the car in the neighborhood in that time. The tank is down to just over a gallon now. I wonder if the old gas has gummed up the carburetor in that time.
I'll take the carburetor to Bob on Monday. He will rebuild it and...He thinks he might have a Demon core in his stash that may have the parts to get the choke working.
I will report back....
 
Today I pulled the Demon and put on a Holley 750 from my 67 Dart.
It ran lean at cold start but richened up nicely with the manual choke. I was able to start it and walk away and let it run. I haven't been able to do that with the Demon for awhile.
I took the carburetor to by friend. He is going to look around and see if he can find the choke parts.
 
how much initial timing are you running
does the carb have adjustable air bleeds
what jets are you running front and rear
 
These carburetors come with 85 primary and 92 secondary jets. I'm at 83/90 and have had that setup since 2014. 6.5 Power Valve. There are no adjustable air bleeds. Timing is at the same settings I've had since 2014. 17 initial, 33 total.
To recap, up until 6 months ago, the car could be started and it would run okay with a little feathering of the throttle for about 30 seconds, then it would idle on its own around 800 rpms, going to around 1000 once it warmed up. Lately, it runs as if it is hitting on 4 cylinders, the air fuel gauge reads WAY lean and it takes several minutes for the engine to smooth out and idle on it's own.
The lean A/F number has me curious. If it was overly rich, I'd suspect a fouled spark plug or some other ignition problem. I have messed with the idle mixture screws to get it to idle in the 13.5 to 14.5 range.
I have not driven the car much in the past year. I wonder if the gas has gummed up a passage or eroded part of a gasket.
The guy rebuilding the carburetor is Bob at "The Carburetor Factory" in Citrus Heights.
 
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