525cfm Demon Carburetor - good for the Y?


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By Daniel Jessup - 18 Years Ago
I have my intake, I have my linkage -my baby Y is hungry for a 4 barrel! Anyone running a Demon Carburetor on their Y block? A fella has a 525 cfm Demon Carburetor. Not knowing much about this brand, what can you all tell me? I have mostly dealt with stock Ford carbs.

Dan

By Ted - 18 Years Ago
I have the 525cfm Road Demon Jr. on my 272 and has proved itself in being a good all around performing carbureter while also providing better than average fuel economy.  The Demon carb does like more intial ignition timing though so don’t be scared to throw more timing at your combination.  I did have to modify the ported vacuum hole so it ended up lower in the bore and closer to the top side of the throttle blades as the original hole was initially too high and not providing enough vacuum to the distrubutor under light cruise conditions.
By pegleg - 18 Years Ago
I have an 850 on my pro street windsor powered Ranger. It's been absolutely bulletproof. I've been extremly impressed with the quality and engineering in Barry Grant's stuff over the years. He's making better stuff than plain Holleys any more.

     Ted what is the size of the primaries on the 525? And maybe you could offer to move the vacuum ports for some of these guys, that mod might be hard to duplicate without guidance and tools.

By Ted - 18 Years Ago
Frank.  I thought I could just look up the venturi size in my Demon book but the reference book I have was printed before the 525cfm was available and subsequently only lists the 625 Road Demon specifications.  I'll see if I can dig up a picture of the last Demon I modified in regards to the vacuum port hole.  I've done this modification a variety of ways over the years but have simplified it somewhat where it's not as complicated but still involves drilling a precisely located hole within the throttle bore.  I'll post more on this as I find the appropriate pictures.
By pegleg - 18 Years Ago
Ted,

        The reason for the question is that I keep seeing questions on this carb versus that carb on this engine. If we can establish what basic venturi sized primaries will work with 272,292, 312 etc. We can print that info and simply reference people to the article. Realizing that each situation is somewhat different (gearing, cams, tolerance for flat spots by the driver) blah, blah, it might be possible to build a chart or publish a list of carbs for various combos with some basis in (empirical) fact. I see an article for here and YBM coming.

By Daniel Jessup - 18 Years Ago
Hey guys - thanks! I thought I remembered, Ted, that you had a 525 cfm Demon on your driver. What about using the port off the spacer under the carb for dizzy vaccuum advance?

Old "pegleg" - you are right on the money with that chart - it would give us greenies a nice little reference.

Dan

By pegleg - 18 Years Ago
Dan'l,

          The port Ted's refering to is above the throttle blades, this is called "ported Vacuum." the plate gets you manifold vacuum. Ported vacuum wrks at cruise but not idle, manifold will add advance to the idle. Some engines don't like that. 

By Daniel Jessup - 18 Years Ago
thanks for that clarification.Wink
By Ted - 18 Years Ago
Daniel Jessup (9/9/2007)
Hey guys - thanks! I thought I remembered, Ted, that you had a 525 cfm Demon on your driver. What about using the port off the spacer under the carb for dizzy vaccuum advance?

Like Frank said, the hole I’m referring to is located above the throttle blades in the carburetor.  The Demon carbs have traditionally put the ported vacuum hole too far above the throttle blades for my liking and subsequently have a weaker vacuum signal at that point as opposed to putting the hole just above the throttle blades when they are at the idle position.  To drill the new hole, I’ve been pulling the base plate off of the carbs so I can get access to the topside of the blades and then drilling this new hole to align with the original passage going to the outside of the plate for the hose hookup going back to the distributor.  After doing this, I simply block the passage going to the original ported vacuum hole.  I thought I might have a picture of the modification but didn’t find one.  The next time I have one of these carbs in the shop for this modification, I’ll be sure to take some pics.