LAvetteman

Which is better for my engine and why?

Corey_68

Joey, I'd go with the 850 on your BB. You can always jet the carb down if needed. If you ever step up the a hotter cam, you'll need it at the higher rpm.

How the car been running? I got my 4spd, clutch, PP, bell houseing, flywheel, hurst shifter and pedals today. Hopefully the BB wil go in soon.

:cheers:

vettedreams

That"s a good ? I"ve got a BB 454 crate motor in my "71, have both the 850 Holley( accually it"s an early model carb may be 840) and the other 850 dp Demon. Cann"t tell the difference though.

Les

With your cubes & "Big Cam" your motor would do quite well w/ the 850. Hit up their techs for specifics- they definitely steered me right back in the day when they were known as Barry Grant carbs. :cheers:

LAvetteman

Great to here your project is coming along Corey. I am sure you are eager to get it on the road, I am for ya. Car hasn't been running great at all, but I think we got it figured out. It has always had a jitter at about 3,000 rpm that turned into a miss a couple of weeks ago. Lars diagnosed it as a weak spark and he was right on, I was only getting 2-4 volts at my coil.(MSD said I should have 450-500) Last week I made up my mind to send the box off as several forum members suggested(thanks again guys). I tried to run her before I pulled the box off, and no fire. I think that box has been going out for years now. So while MSD has my box I figured I would use this down time to get a carb in and be ready to change it after I get the box back in....

That old holley has been needing a replace ever since I got my vette(over 2 yrs) and rebuilding just ain't worth it, it been leaking pretty bad. I tell my wife its more of a safety issue than performance. :jester ;)

Hey, did you hear they closed down the track in Eunice??

Glad I took a spin before they killed a legend.


[Modified by 71,454,4spd, 9:41 PM 12/16/2002]

JoeC427

Joey, I'd go with the 850 on your BB. You can always jet the carb down if needed :yesnod:

Corey_68

:lol:

I'm glad they shut it down before someone got hurt.

No Problem shut down for a month, they will re-open January 16. We need to get together with the Louisiana crew after it opens back up.

They cheapest place I found for the 850 Demon was PAW http://www.pawengineparts.com/

I purchased it from them for $425, no shipping charges. Just make sure you order the fuel log to go with it, as I found out the hard way the Holley fuel log will not work. :mad

:cheers:

Vetterodder

I agree with the others, your engine can use an 850. Because your engine has the cubes and also high rpm potential. it can use more cfm than a smaller and/or milder engine. The larger throttles also result in less pumping loss (less restriction to airflow means that less power is lost due less restriction of the pistons downward movent in the intake stroke). Over-carbing an engine is a problem because the lower air velocities make it difficult for the carb to properly meter the fuel. With your cubes (and the greater airflow velocity that results) you shouldn't be over-carbed at 850. While the smaller carb would likely give better throttle response at low rpms, unless you're over-cammed for your gears, I'd expect that you would already have more low end torque than your tires can handle.

Smokehouse69

850, Demon recommends 750 for the ZZ4, so your 454 should certainly handle an 850.

LAvetteman

:lol: :lol:

Yea, no need for speed bumps on a drag strip!!!! :lol:

Thanks for the info on the fuel rail, I was about to make that mistake. Looks like the same thing.

Thanks

I would have thought Mike would have got us together at hooters by now, maybe he is still busy. :D

Sigforty

Smokehouse69, I do not think Demon recommends their 750 for the ZZ4 because they actually make a special 650 for the ZZ4 in both mechanical and vacuum secondaries. I put the ZZ4 650 on my car with the mechanical secondaries and it rocks. It works alot better on the car then the Road Demon did. I cannot believe the change from vacuum to mechanical secondaries. The four speed just loves double pumpers. Joey, I would try a 750 on the 454. Demon carbs flow better than the Holleys. I think it is a lot easier to overcarb a motor with the Demon because they are so good.

Mark B.

LAvetteman

Thanks for the advice Mark. You are the second person to suggest the 750 instead of the 850. You and LARS.

What to do?
What to do?

Anybody have contact info for BG?

71vettman

I had a 750 speed demon on my 454 with a pretty highflow setup. I origionally had an issue with a overly rich idle I think it may of been due to my cam mostly though. Any way I dynoed the car and planned to run it to the 6000 rpm range and ended up bringing it up to only 5000. The reason I didnt run it higher was because my air fuel ratio at its lowest point was 13.6:1 which is kind of high. The worst part was that by 5000 rpm it had climbed to 14.7:1 :eek: This was with the stock jetting and with no real tunning. The hp was climging very steadily and hit 331 at the wheels before we let off the gas. I was going to change the jets but I personially felt the need for the 850. So now I have an 850 on my car and I can feel a definite power difference for the better. My peak torque was 401 at 2500, I havent dynoed it again but it feels like my peak torque now occurs about 1000 rpm higher at 3500. So far I am pleased with the 850 over the 750.

427Hotrod

I know I won't be popular here among all the Demon lovers, but I'd get an HP series Holley in a heartbeat over a Demon. For every person I know of with a good one, I seem to hear of five that hate them. And msot have absolutely terrible things to say about BG tech support. I'm sure glad some of you guys have had better luck. Maybe they have improved. I know Lars likes them, but they just don't do as much for me.

They have many many features, and this allows many tuners to get them way out of whack easily.

Ckeck with Vettemaniac here on the Forum for his experience with one of my homebuilt 850s versus his 850 Demon.

For sure the 750 is a nice conservative approach to a 454, and will run well. But the 850 or 950 will spank it badly.

For sure get a Double Pumper version. You can handle it.

HP series 950 if it was me. Or maybe an annular 830/850 for great response.

JIM

LAvetteman

Thanks 71 vette, you talked me into it, sounds like real similar testiment to me.