Holley vs Demon

[joea]

I've been trying to find some decent information comparing carbs. I hear that Holley's require alot of tuning maintenance but are a fantastic carb. What about the Demon? I hear they are easier to tune than the Holley and the replacable venturi sounds like a great feature (ususally only see this on Webers). My application will likely be a 427 or 428.

Can anyone comment or point me to a good source of info?

[Tom Wells]

Hi joea,

I'm in the process of dumping my Demon 850 vac sec from my 521

It is being replaced with an MPFI mostly from Holley. Ask me again next month if I like the MPFI

The carb gave me the most enviable idle - great noise and vibration - verrry intimidating to anyone around the car

Alas, it had a hesitation I lost patience with. Probably some carb Xpert could have made it perfect, but mine ran out Also, there were several threads stripped during the dis- and re- assembly, in the air horn and bowl that required heli-coils - altogether frustrating

Don't know if this helps but there it is

Tom

[marty]

I am running a Demon Race 675. Love this carb .... easy to tune and very stable.

[Back in Black]

I have been told that that the quality of holley carbs has gone south over the years, but I have not really seen this myself.

My West Coast cobra 514 motor will initially come with a demon 850 in place of the throttle body, but I will be dumping it asap after break in, for the holley throttle body EFI. You can have it then, if you want it . I actually hate carbs generally, antique little buggers

[Tongue Pirate]

Both are great carbs & I would say that niether need a large amount of tuning. If you are concerned about vintage appearance Holley is the only choice but if it is racing perfomance out of the box I would be more inclined to go with a Demon. They have taken every step possible to improve on the Holley design & give it to you at an affordable price.

[Mr.Fixit]

Holley run fine right out the box on 90% of V-8's provided you picked the right size carb, (no 850 DP's on a 289's). Demons REQUIRE you to tune them. The holley will work alot better if yoy do tune it, of course. Demons have little issues I don't like: their bowl screws are too short and strip out, needing helicoils. They look "wrong" for a restoration or vintage application. I hear guys get a little more HP out of a well set up demon on the dyno, but I have seen several that were swapped out for mildly reworked holleys much to the delight of the owners. Holleys have not been going down in quality. Besides, there are a million of them out there, waiting to be rebuilt. I just have not been impressed with demons yet, but they are better than the BG carb that came right before the demon, the one that holley apparently (or so the rumors were told) sued over, making BG change the appearance slightly so it wouldn't be a copy. I know of one of those for sale or trade for equivilent holley.

[SCOBRAC]

Would be perfect for your dual quad motoring pleasure EXCEPT the very stylized sculpted float housings do not clear the 8V linkage assembly.. Alas it is unlikely anyone will come up with a matching linkage.

[Tongue Pirate]

I was told that the early demon carbs had problems with the float bowl bolts stripping out but that has long since been fixed.

[joea]

How big of a factor is the replacable venturi? In my limited knowledge of the subject I picture being able to have a race setup and a road setup or is that more work than anyone would go though and just go with something between the two?

[Mr.Fixit]

The repalceable venturi for for serious tuning. You better have lots of experience, and a racetrack or dyno. They let you vary the CFM rating of each barrel on the carb. Honestly, most guys never get their carbs dialed in for their particular setup. Most people don't even re-jet them, or play with pump cams and squirters. Being able to tune CFM seems pretty unimportant given the tuning capabilities most owners refuse to use. The setup that works well for your combo, will work on the track and the street, unless you swap motors out between venues.

[joea]

Now that I got you all hooked, anyone care to comment on mechanical vs vaccuum secondaries? My understanding is vaccuum is more reliable or predictable? Is mechanical better for performance?

[Tongue Pirate]

iF YOU GET THE CORRECT SIZE CARB FOR YOUR CAR(SORRY!) vacuum secondaries should work great & save you a little fuel. On the other hand with Manual Secondaries you get that gas when you ask for it. Really depends on where the brain is located in the body. BTW mine is somewhere mid leg

[Mr.Fixit]

Depends on the motor and the car. A relly hot motor in a light car with good gearing wants mechanicals. A heavier car with a milder motor and more reasonable gearing prefers vac secondaries. This is a generalisation, but you get the idea.

[Hal Copple]

Re the mechanical/vac secondary thing. I picked up over hp and # torque when i replaced my vacuum secondary spring with the lightest "white" spring on my 303 motor. I have now a HP Pro 750 vac secondary Holley, and perfect drivabilty, response, and tons of power. Did not take much more than slightly leaner jets, and another White spring, and tweak the squirter spring bolt.

I have heard from several experienced engine guys that for unknown reasons, some engines seem to prefer one or the other Carb, Demon or Holley, by the way.

So i was talking with another engine guy about my "white spring" change out, and picking up power, and he said if by opening up earlier, with the lightest spring, what would happen if i could put in yet "lighter" springs, would that give even more power, by bringing in the secondary's sooner? Then would not at some point then just going to a mechanical secondary be the same as some ubelieveably "light spring"??

Sounded like a good anology. He happened to mention that his days with a mechanical showed to him that as along as he used some judgment about tromping on all four barrels at too low an rpm, he never had "bog" or driveability problems.

But for me, who is not so experienced, i can indeed tromp on the gas, and let the carb decide when it wants and needs more air. He did comment the extra gas used was substantial, and if not consumed, could possibly cause rapid cylinder wall wear due to lube wash-off, and further gas contaminate the oil.

So i think unless you intend to run all day at high rpm, heavy throttle, a Vacuum secondary with a "white" spring is a better choice.

Like thinking about a single plane vs. a dual plane manifold. The former may give a bit more "top end" but probably gives up some lower in the rpm range, where in all liklihood a motor spends the vast amount of time.

I personally think one should very carefully think about what rpm and how the car's power will generally be used, and then select components on that basis. Just more power alone may not make for a very useful car.

[Hal Copple]

ah rats, i left out some info from my above post. I picked up over 40 hp and an equal amout of torque pounds, and my engine is a custom 396 ci motor.

Hard to proof read one's own typing, i guess.

[jwoodard]

750 CFM Speed Demon on a FE390. That's after trying an Edelbrock and a Holley. Mine has mechanical secondaries and it is by far the best carb for my car yet. I did have to do some tuning on it to get it dialed in, but it ran great out of the box. I thought it was running rich, but after a dyno pull found out it was lean, so went up in the primaries and squirters, gained 20+ RWHP and RWTQ and it is great.

Jim

[SCOBRAC]

I saw today in Hot Rod Magazine Barry Grant has replicated a three duce set up.. No specifics were given except to say total cfm was 1050 (350 x3).. Interesting..