Demon Carb identification help needed

Posted By: Finoke

Demon Carb identification help needed - 10/20/14 04:35 PM

I got this Demon Carb with a parts lot that I picked up over the weekend.

It doesn't have any identification numbers around the top air horn.

Can anyone guide me on how to identify this carb and how to tell what SCF rating it is?

Any input is appreciated

Attached picture 8306266-20141020_094438.jpg

Posted By: Finoke

Re: Demon Carb identification help needed - 10/20/14 04:36 PM

Attached picture 8306267-20141020_094424.jpg

Posted By: Thumperdart

Re: Demon Carb identification help needed - 10/20/14 04:50 PM

Looks like a speed demon...............

Posted By: cruzin

Re: Demon Carb identification help needed - 10/21/14 12:55 AM

Most likely it's a Speed Demon 575 or 650. Down leg or annular booster?

Posted By: rickraw

Re: Demon Carb identification help needed - 10/21/14 01:37 AM

Measure the throttle bores & do a search.

Posted By: Finoke

Re: Demon Carb identification help needed - 10/21/14 04:55 AM

Quote:

Down leg or annular booster?

I'm not sure what that means. I'm showing my carb ignorance

Posted By: Finoke

Re: Demon Carb identification help needed - 10/21/14 04:56 AM

Quote:

Measure the throttle bores & do a search.

Will do. So is throttle bore the main influence on the CFM rating?

Posted By: cryplydog

Re: Demon Carb identification help needed - 10/21/14 07:01 AM

do not measure venture dia. measure throttle plate dia.

Posted By: Hemi Allstate

Re: Demon Carb identification help needed - 10/21/14 04:28 PM

It looks to be a Speed Demon
With the butterflies showing 1.69 I figure that to be 1 11/16".

I have the chart showing 1 11/16" vacuum sec. being either 650 or 750 CFm depending on venturi size.
650 is 1.28 and 750 is 1.40 venturi
Boosters are downleg
650 is .140 750 is .160

I hope this helps.
Mark

Posted By: Finoke

Re: Demon Carb identification help needed - 10/21/14 07:59 PM

Quote:

It looks to be a Speed Demon
With the butterflies showing 1.69 I figure that to be 1 11/16".

I have the chart showing 1 11/16" vacuum sec. being either 650 or 750 CFm depending on venturi size.
650 is 1.28 and 750 is 1.40 venturi
Boosters are downleg
650 is .140 750 is .160

I hope this helps.
Mark

So I found an identification chart on the Internet. A small number 6 is cast on the top of the carb meaning it's a 575 or 650 speed demon.

It's a 575 if the booster is annular. It's 650 if it's down leg. So it sounds like it's a 650.

What does each type of boost Venturi look like?

Posted By: Hemi Allstate

Re: Demon Carb identification help needed - 10/21/14 08:27 PM

From what I can see of your above picture yours are down leg.
Annular boosters are larger in diameter, and thicker, and that is why the reduced CFM rating when they are used.

Mark

Posted By: Finoke

Re: Demon Carb identification help needed - 10/21/14 08:52 PM

Quote:

From what I can see of your above picture yours are down leg.
Annular boosters are larger in diameter, and thicker, and that is why the reduced CFM rating when they are used.

Mark

Nice, thx!

Posted By: Hemi Allstate

Re: Demon Carb identification help needed - 10/21/14 08:57 PM

One more thing,
I don't show the 575 CFM annular booster as a vacuum secondary carb either.

Mark