As a rule, never wire the electric choke to an ignition circuit.  This creates a voltage drop which potentially either causes the ignition module to fail prematurely or just creates a situation where the engine misses due to not having enough voltage to the ignition coil.  An electric choke needs to wired to a circuit independent of the ignition but still turns on and off with the ignition switch.

Lorena, Texas (South of Waco)

I just put a Holley 390 on my stock as a rock 272. I put an electronic ignition module in it with new 7mm plug wires and Autolite platinum plugs. Everything is fine. Started right up and runs strong. Not sure about that electronic choke yet but so far so good. Has enough get up and go for me. I have it on top of a 1" spacer. Tons of torque, but it is a torquey old motor anyway. And it looks pretty ..

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

i cannt agree more on the demon carbs they are slick and nice thats what wil be going on my 55 vic as soon as i get the intake changed over

y-block newbie

The gaskets, needle seats, jets, and power valves are basically interchangable between the Holley and Demon carbs.

Lorena, Texas (South of Waco)

Thanks, Ted. If it worked on your 254 deg cam then I probably will not have much trouble. In fact, I was looking at my Edelbrock book last night and it says that the 600 I am currently using is for cams with less than 220 degrees as well. I'm also curious about what makes the difference between the edelbrock 600 and 500 carbs. The book says that the primary and secondary bores are the same, as well as the venturi diameters. An Edelbrock 500 will be easiest for me to swap but if you all are having good results with the demon...

Do the Demon carbs use Holley jets and power valves? I haven't noticed any Demon jets or valves.


Lawrenceville, GA

I just put an "out of the box" Holley 390 on my 272 with a 57 up manifold. I converted the ignition to a 57 up distributor with a Mallory electronic kit, new MSD 7mm plug wires and Autolite platnium plugs. Fired right up, set the timing and am good to go. Works fine and I never fiddled with anything.

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

 

Ted,

I didnt intend to reinforce/perpetuate that myth; sorry if it came across that way.  I certainly understand/agree with your (and others) previous explanations on bigger carbs running leaner.  I was just commenting on how my 500 cfm showed a LOT of fuel dilution on a UOA vs. the 390.  May have been as much an issue of the carb itself as the size...

I have yet to find a setup that is really all I want it to be; for starters I cant really pull much more than about 10 in hg at idle... but that is a question for another thread!

 

Ron Grove

Wauconda, IL

Charlie.  The camshaft in my 272 is 216° @ 0.050” with the lobe centers being ground on 108° and the 525 cfm Demon Jr. is fine with this.  There will be a certain point where the manifold vacuum drops off enough that the idle bleed holes will need to be tinkered with and this is where screw in air bleeds would be nice.  But those screw in air bleeds would appear to only be available on the higher end carbs and those of a larger cfm capacity without going to the trouble of retrofitting a non-equipped carb with them.  With the pressed in bleeds, it’s trial and error on addressing idle and low rpm fuel mixture issues with a much larger than normal camshaft.  Changes are typically made in 0.003" increments.  But  if it makes you feel any better, the Road Demons and Speed Demons basically have the same size idle bleeds and I have ran both on a Y with the 254° @ 0.050” camshaft without major differences in idle quality.

Lorena, Texas (South of Waco)

With regards to grinding the manifold,  if you want to get better performance with the Iron manifold grind the flange area out like this.  Be sure to remove the sharp end edges where the holes enter the "roof" of the passage.  Also eliminate the pinch point where the passage dives down and under.  Your can just see that place in the pic in the right passage.  I glass bead and fill the flange with high temp epoxy mixed with the iron filings that result from the grinding. This has not been done on this manifold yet.

Use a plastic spacer under the carb. 1/2 or 1 inch max performance is a single square hole spacer.  Smoother operation is with a 4 hole spacer and is recommended for street.

These modifications will support over 300HP with other engine mods. And with a proper metal spacer this could probably be done to '55 and '56 manifolds also so that a more modern carb could be used.

Doug T

The Highlands, Louisville, Ky.

Thanks Steve,What is required to match manifold to carb?Boring the holes larger in the manifold or can the spacer be tapered to match carb on one end and smaller holes in the manifold on the other?Thanks for your help.Regards Mark