rainman69

Just simple question(s):

Holley or Speed Demon for a dual street/strip Corvette? Why?

ZORA_RULES

Unfortunatly my new SD 650/vac secondaries is still sitting in the box...won't be able to install it till next week. I think it depends on which Holley you're talking about....the new street avenger sounds pretty cool. I had an older version Holley on my 70 and wasn't crazy about it...ran great when tuned but required tuning a lot. But I would imagine oppinions here will be varied a lot, as holley's have done great for years....but the Demons are great as well from everything I've read on them.....hopefully I find the same experience.

Clink69

I have the Street Avenger (Holley) and so far would recommend. Especially for the price. Easy Jet changes. Forget the elec choke, I milled that off....

:flag

vettecor

Holley should be cheaper, but I would go with the Demon. I plan on a 650 this Summer.


Larry :seeya

compuvette

Got a Holley 80508 (750 vac. sec. electric choke) going on the 412, but lars tuned it and tried it out on Jeffs 66 427 and it ran great! But the whole time Jeff kept telling me that his BG was better. He said mine ran really good "for a Holley".

Sigforty

I just bought a road demon for my 350 and it runs awesome. It cost me about 100 dollars less than the speed demon. The only thing I can say about demons is use a less cfm rated then you think. I know some people who put 750's on 383's and bigger motors and had a horrible experience. The people at demon recommend the 750 for a 500 hp 454.

Mark B.

verskel

Based on the above comments,
Does this mean I need to 'trade-in' my Holley for a Speed Demon ? :confused:

71roadster

I just replace my carter 625 with Speed Demon 750 VS and it instanly made a difference and this is on a 350. I am building a 383 which is why I bought a 750. I have never heard of a bad experience with a demon and a lot of folks on other boards are saying BG is telling them to run an 850 on anything bigger than 400ci, so I think the 750 will be perfect for a 383.

Chris

rainman69

Interesting...because BG recommended a 750 Vac Secondary Speed Demon for my 355, which is producing 400+ HP. I know it's "too big" per the equation for CFM, but I figure that the boys and gals at BG know their stuff.

dman535

Hmmm

Based upon this profile :
355 ci 9:1
World Sportsman II 2.02/1.60 heads
Comp Cams XR-282 Roller Cam .230 .236 (.050)@ .510 .520 I/E
Weiand Stealth
Edelbrock 750 cfm carb
HEI
1 5/8" headers - 2 1/2 " True Dual Exhaust
700r4 Auto
3.55 Rear Gear

They reccomended a 650 Speed Demon. I have a 400 sitting in the garage, I think I just might end up going with the 750 for the sake of spending major $$ for a carb that will work on both motors.

robzr

My .02 on Demon Vs Holley and if it's worth it, it really depends on how much money is worth to you. Demons have some real nice features (4 corner idle, billet metering blocks/baseplate, beautiful design), but they really are just fancy Holleys. Not a huge world of difference between the two. I ran a few Holleys before I switched to my Speed Demon 750 and I love the Demon. I am selling it soon though as I'll be switching to EFI.

Rob

74vetteman

On the dyno, my 406 made 476 hp and 494 tq with a 750 speed demon double pumper (no choke installed). We then bolted on the dyno operators Holley 750 double pumper (with open choke), and made 469 hp and 490 tq. We didn't try to jet the Holley but it was fairly close already. The dyno operator said that this was the first time he saw another 750 carb make more hp than his.
We also tried a 950hp holley which made 493tq and 474 hp. Again we just bolted it on with whatever jets were in it.

I guess the point made is that the Demon just isn't that much better a carb than the Holley. If we played with the jetting, we might have made more hp, or we may have lost some. These were also carbs that had been around a while (the Holleys), so maybe the new ones are even better.


[Modified by 74vetteman, 12:15 PM 4/6/2002]

rainman69

When you get in to the nitty gritty of it, Barry Grant used to work for Holley unless I am totally insane. It's my understanding that he broke off on his own when they didn't like some of his ideas...so he made the Demon.

Someone correct me please if necessary? Thanks, I was just looking for a general opinion. :cheers:

robzr

I'm no better with history than you are ;) But I think BG used to sell modified Holleys, or he built his own version of the Holley until they sued him. He had to change a bunch of things, and I believe the result of that was the Demon series.

Rob