Holley vs Demon?

**TDW** · #1 03-20-2012, 12:56 AM

I have a 750 Demon on a 500 HP 427. It seems "sluggish" on take-off. It is a double pumper. I have been reading about the new Holley Ultra series. The reviews are pretty good. I am wondering if the 4 corner idle is a big improvement over the old style Holley. I have a decent 4780 that I thought about sending to Eric for a freshen up. Anyone have any real world experience with the 3 different carbs? Or even a vacuum secondary Holley? 427, 4 speed, 4.11 gears. 3400 lb Nomad is what I'm playing with.

**69 Post Sedan** · #2 03-20-2012, 01:04 AM

I'm sure a lot of more experienced carb guys will chime in but I have heard nothing but bad things with Demon carburetors.

I would get rid of it and install a Holley. :twocents:

Kurt

**PxTx** · #3 03-20-2012, 02:10 AM

I have had good luck with both Holley and Demon carbs. The ones with more adjustment are nice to dial in, but I wouldn't get rid of a good carb just to gain 4 corner idle.

Those Innovative wide band O2 sensors can really spoil a backyard guy and help dial in your tune or point out where you need some adjustment.

What type of ignition tune are you running?

VintageMusclecar · #4 03-20-2012, 02:58 AM

Tony;

What's the stats on the 427?

Unless it's a relatively serious build, I would probably lean towards a good 780 vacuum secondary for overall street manners.

The 4 corner idle is nice on a wild engine but is unnecessary for 90% of "real" street applications.

Eric

**Lynn** · #5 03-20-2012, 04:31 AM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TDW</div><div class="ubbcode-body">I have a 750 Demon on a 500 HP 427. It seems "sluggish" on take-off. It is a double pumper. I have been reading about the new Holley Ultra series. The reviews are pretty good. I am wondering if the 4 corner idle is a big improvement over the old style Holley. I have a decent 4780 that I thought about sending to Eric for a freshen up. Anyone have any real world experience with the 3 different carbs? Or even a vacuum secondary Holley? 427, 4 speed, 4.11 gears. 3400 lb Nomad is what I'm playing with. </div></div>

427 4 speed Nomad? I think I see the problem here. That car is REALLY tired of Michigan winters. You need to send it down to Oklahoma with me for about a year (don't forget to send some cash for tires, as I have a feeling those rears are going to need replaced regularly). I promise to take real good care of it (except for those rear tires). Oh, and I have two really nice 780 vac secondary carbs to try out on it. One of them was done by Eric, so it should be perfect!

**TDW** · #6 03-20-2012, 11:50 AM

Thanks for the replies. Here's the engine specs.

1978 445 casting, 2 bolt block, line honed, ARP studded mains
Resized 3/8 truck rods
6223 GM crank
Fed Mog Competition bearings
.030 SRP medium dome pistons. JE file fit rings
Balanced assby
9.75:1 comp
Merlin oval port cast iron heads
Howard solid cam (245/252@ 0.50,587/578.110 lsa
Howard billet 1.7 roller rockers
Howard custom length hardened pushrods
Howard EDM lifters
World Products dual plane intake BG Speed Demon 750 mech secondary
Milodon HV oil pump
All ARP fasteners
GM points type ignition, set-up by MacNeish. 18 initial, 36 total, VA hooked up and working

Made 501 HP @ 6300 rpm,510 lb-ft at 4000 rpm

Eric, the Holley site also recomends a VS carb for the street, due to the weight of the car?

**TDW** · #7 03-20-2012, 11:54 AM

Lynn...There are some pictures of the Nomad in the MR section. Have a quick look at them. The car is a blast! I keep it in a temp controlled garage, so the Mich winters treat it OK, but thanks for the offer!

VintageMusclecar · #8 03-20-2012, 02:36 PM

Nice build.

How much vacuum does it make at idle and what trans (ratios)?

I'd really be leaning towards a 780 from what I see at this point. A 3310 with an electric choke would work mint and be about as fussy as an anvil. The 800 DP could go on without much drama but a 780 would still provide better manners and probably mileage as well. (Of course the 800 could be tweaked to clean it up down low also)

I know there are a LOT of nay-Sayers out there who are quick to poo-poo a vacuum secondary carb (much as the oft-maligned Quadrajet, i.e. "Quadra<span style="font-style: italic">junk</span>, Quadra<span style="font-style: italic">bog</span>, etc.).

I really need to get a video up of my Chevelle while driving to show how well one can work.

Eric

**TDW** · #9 03-20-2012, 03:07 PM

Thanks Eric. I don't remember the excact vac , but I am thinking 10-12 inchs.

The engine is the one that Tony(Scuncio) did for the Sept. 04 Chevy High Performance article. The article is called "500 HP-Low-Buck Big Block".

I have a pretty decent 3310-2, 2156, that it looks like I will be sending you for a freshen up.
What is the vac number I will need for this application?

The trans is an M22 that I bought from our own Chuck(427 King) a few years back.

I appreciate all of you guys time.

**69 Post Sedan** · #10 03-20-2012, 07:18 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: VintageMusclecar</div><div class="ubbcode-body">I know there are a LOT of nay-Sayers out there who are quick to poo-poo a vacuum secondary carb (much as the oft-maligned Quadrajet, i.e. "Quadra<span style="font-style: italic">junk</span>, Quadra<span style="font-style: italic">bog</span>, etc.).

I really need to get a video up of my Chevelle while driving to show how well one can work.

Eric </div></div>

You are spot on Eric. A lot of people think they need a double pumper. It's similar to needing 4 bolt mains or a steel crank....for most street motors, it's not necessary. A properly tuned V/S works fantastic. Ask me how I know....(insert plug here) thanks to Eric! [img]<<GRAEMLIN_URL>>/grin.gif[/img]

Kurt