jpony645

I'm going to give this a shot over here since it only got 2 views in Mustang chat. Sorry for the double posting.


I'm pondering (been around Lman too much) about going with a Demon carb in place of the 600cfm Holley I had. I'm just not sure which one I need to go with, the Road Demon jr, Road Demon, or Speed Demon. What are the differences in the 3?

I also think I need something in the 500-600 cfm range based on my engine mods. Would 650 be too much?

'65 289 block
.040 over with flat top pistons
.010/.010 under crank
.204/.214 dur. / .448/.470 lift cam

'65 289 iron heads
stock springs and rockers
triple cut valves
shaved (not sure of the amount but just enough to ensure flat surface)


Opinions?

Jay

Your car is not going to be roadworthy for sometime. One thing I have learned is not to buy in too early. By the time you are ready they will have improvements/new models/etc. at lower prices.

650 is too big for a Demon there. Demon themselves will give you the best recommendation on size. Don't think a Speed Demon is what you are after either. I don't have experience with the Road or Jr.

Nixon

For what it's worth.... here's my setup...

302 block, .030 over... flat top pistons... 9.5:1 (or so, maybe a little closer to 10) compression...

1970 351W heads, stock valves, 3 angle jobber, hardened seats, etc, etc...

Cramecams Energizer 272H10

Lift: Intake @Cam 3027 @Valve 484
Exhaust @ Cam 3027 @Valve 484
Rocker Arm Ratio 1.6

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 27 BTDC 65 ABDC 272 °
Exhaust 67 BBDC 25 ATDC 272 °

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 3 BTDC 33 ABDC 105 216 °
Exhaust 43 BBDC (7) BTDC 115 216 °

yadda yadda yadda... I got a Speed Demon 650 cfm carb from a VMF'er... (I bet you'll chime in here askin' for his $$, it's in the mail!) and I have had no problems with it. Good response and all that. Granted, it hasn't been dyno'ed and tuned very much, so maybe I'm running super rich/lean through the acceleration curve... But I haven't noticed any hesitations or bog downs because of it...

Just thought I'd throw that in.

67shelby

Remember too that you'll need less carb for a AT than a manual. You didn't list what you have in the question, and I don't recall if you have put it in previous posts. My 67 Shelby GT350 as a 595 CFM Holley because it is an AT. The manual 67 GT350's got a 715 CFM Holley.

jpony645

It's an automatic.



Jay, I'm fully aware that I don't need it right now. I've been told that already.


I was just doing a little thinking while in my quiet place. B)

Jay

Never hurts to think... that was more general adcvice for the populace at large

jpony645

Torquewrench

Since you're using stock heads and didn't mention porting them, and you're using a fairly tame cam, I wouldn't think you'd need to go over 600. Maybe 550 would be a better match. Now if you increase your cam duration or change the heads so the engine flows more, then you'd need to consider supplying more gas.

jpony645

Not much selection in the 550cfm range though. You either have 525, 600 or 625. Holley offers a 570 in their Avenger line up but I'm not a fan of Holley based on my previous experience.

I'd really like to know how people like the Demons and how easy they are to tune.

Sharp

I put the road demon on mine. I have a 351C 4v with an automatic. I love it. You'll have to get one with the automatic linkage hook up. Don't forget to order the ball stud kit to snap the linkage to the Carb. I had my original carburetor rebuilt by Pony Carbs and it didn't run any better than when I sent it out. I waisted about $400 on that old carb.

jpony645

Let's see if anyone has anymore information on this.......

bnickel

i've got the 625 road demon on 351w and it might be a bit big for the cam/compression i'm running. i would suggest the 525 RD jr for your car. especially since it's an auto. the kickdown linkage on the RD isn't easy to hook up, you basically have to relaocate the entire carb linkage including the kick down. that's ok for a car with a kickdown cable but mine uses a rod and i'm not about to try and bend the rod or fab a new either, so right now i'm not using one. the RD jr is identical to the 600 holley as far as the kickdown so it is a 100% bolt-in. the road demon, speed demon are just like the dual feed holleys in that respect