Thoughts on Demon carb?

[iskwezm]

what the hell is it? i like those big ass annular boosters, i bet they make HUGE power. annular boosters are the way to go, especially on a street motor. but i doubt this thing is going on a street motor, then again mybe that's why it's so overkill.

Its a street engine, he drives it up and down the street once a month

actually its a 540 BB chevy in 69 Camaro with a 22 psi Procharger dynoed at a little over 1660 FWHP.The carb is made by The Carb Shop and has their new billet bolws and dual needle and seats. Yes it is overkill

 

[10secgoal]

Looks like a E-85 or alky carb

 

[jbuening]

AFAIK, Demon carbs had major quality control issues (like shavings plugging the carb) and got so bad that Summit Racing no longer carries Barry Grant carbs. I have no direct experience with them though. I'm in the process of swapping out my 600cfm eddy for a 670cfm Street Avenger.

 

[htwheelz67]

thats just gossip, BG has corrected the QC problem a long time ago and the reason summit doesnt carry them is BG dropped them because of pricing issues, Jegs and others sell tons of BG carbs. That summit story has been floating around for a long time which isn't true.......

 

[10secgoal]

what was your setup, and what demon carb did you use?


and 10secgoal knows alot about this carb stuff, where's he at??!!!!

Sorry man, have'nt had much time to post.I didn't even see your post here. Saw that carb Mario had had to say something. I've stayed away from Demons for the reasons mentioned before. And for that reason is the same reason I don't recommend shiny Holleys. The inside flaks HORRIBLY. I generally tell people if you like to tinker with carbs, a DP is hands down better throttle response. You need to tinker because the secondary pump shot takes a little to tune, where a vacuum sec there is no need. I'd even look into a 750 for that motor. I ran one on my 302 and it verifiably made more power above and below the curve.

 

[mrmustangman357]

Sorry man, have'nt had much time to post.I didn't even see your post here. Saw that carb Mario had had to say something. I've stayed away from Demons for the reasons mentioned before. And for that reason is the same reason I don't recommend shiny Holleys. The inside flaks HORRIBLY. I generally tell people if you like to tinker with carbs, a DP is hands down better throttle response. You need to tinker because the secondary pump shot takes a little to tune, where a vacuum sec there is no need. I'd even look into a 750 for that motor. I ran one on my 302 and it verifiably made more power above and below the curve.

BG quality issues? If I went throught the carb before using it, wouldn't that alleviate the problem? I always thought all things being equal, a demon carb would be better, as it is just a holley 4150 only with closer toleranced parts, which I assumed meant a more precise (accurate) system

 

[blown65]

Second the referral of ProSystems. Made 8 more hp, and 30more tq with their carb outta the box vs the Holley we were running. Dyno Chart to prove. hehe The dyno shop here has done a few of their carbs on other motors, and they love them.

650cfm carb making 650 to the ground before nos, someone has been inhaling too much nos.

 

[bnickel]

BG quality issues? If I went throught the carb before using it, wouldn't that alleviate the problem? I always thought all things being equal, a demon carb would be better, as it is just a holley 4150 only with closer toleranced parts, which I assumed meant a more precise (accurate) system

yeah that will fix it if you get one that still has the problem. that was a long while back and i believe the issue has been corrected now. it was a QC problem not necessarily a carb problem.

 

[Tech @ BG]

yeah that will fix it if you get one that still has the problem. that was a long while back and i believe the issue has been corrected now. it was a QC problem not necessarily a carb problem.

That would be correct in that the shaving issue was addressed quite some time ago and several steps were put into place to cut down on them. With machining parts from billet there is always going to be a chance to have a small sliver break loose and show up but most of the shavings customers were complaining about were found on gaskets or came from the way parts were being stored or assembled. We found the gaskets were picking up shavings laying on the bench before assembly so steps were taken to store them in a clean box and remove them at the time of assembly. The way machined parts were being moved within the building was changed and also a sonic wash machine and procedure was added. As we are made aware of or find issues we try to address them in an effort to always improve our products. We are here on the board so feel free to pm,email or call us if you need any assistance.

 

[Tech @ BG]

I am looking into buying a new carb for my 351W. it is 9.8:1 compression with twisted wedge heads and a .530 lift cam at 220 duration. It has an rpm air gap manifold and headers. I had a 750 edelbrock on it but wasn't satisfied with the tuning at cruise. So now I'm finally going back to holleys. I notice Barry Grant has their carb line with specific recommendations for cam duration and such. They recommended me a 650 speed demon with vacuum secondaries. Their carbs are a bit underrated and often flow more than what they rate them for, so I would like to use a 650 for good tuning. I am using a manual trans with 3.73 rear gears. I can't wait to do power tour next year, so it will see some highway miles as well. some people say the demons only run best at WOT, but seeing this carb is recommended specifically for my cam duration and combo, will I have any problems with that? Tell me what you think.

With the manual transmission we prefer to use the mechanical secondary version. The 650 Speed would be a good choice on the 351w.

 

[Tech @ BG]

I have a speed demon 575. Horrible. I couldn't tune it, my mechanic couldn't tune it. I'm going with holley next. I have a 289 though. I suppose BG's are great on certain applications. however, for some reason it wasn't the right application for me. Holley will work just fine.

Typically the 575's work well on both the 289 and 302's .Send me a pm with what kind of issues you are having and we'll try to determine what is going on with it.

 

[mrmustangman357]

hey welcome to the board. its good to have a first tier tech on the board. what are the advantages and disadvantages of using vacuum vs mech. secondaries? I realize mech secondaries work well with light cars and sticks, but can't I use a lighter spring in the vac secondaries to achieve a similar performance? I'd hate to be on the highway with the mech secondaries giving it more flow than it needs

 

[bnickel]

hey welcome to the board. its good to have a first tier tech on the board. what are the advantages and disadvantages of using vacuum vs mech. secondaries? I realize mech secondaries work well with light cars and sticks, but can't I use a lighter spring in the vac secondaries to achieve a similar performance? I'd hate to be on the highway with the mech secondaries giving it more flow than it needs

the mechanical secondaries are just that..secondaries, they shouldn't even be in use when driving down the highway, unless you really have your foot in it, but under part throttle they won't even come into play

 

[Tech @ BG]

hey welcome to the board. its good to have a first tier tech on the board. what are the advantages and disadvantages of using vacuum vs mech. secondaries? I realize mech secondaries work well with light cars and sticks, but can't I use a lighter spring in the vac secondaries to achieve a similar performance? I'd hate to be on the highway with the mech secondaries giving it more flow than it needs

With a manual transmission and autos with converters 3000 and up we see the engine has a different load and the signal is different. A vacuum carb on a stick car acts differently and can have choppy driveability . The vacuum secondary opens as a load is placed on the engine and the air passes past the port in the main body. Think about why you cant sit in the driveway and rev a vacuum secondary and make the secondary open,same affect with the stick cars for the most part. As bnickel mentioned, going down the road at most cruising speeds you wont even have the secondary butterflies open.

 

[fastcoupe68]

My buddy has a race demon 650 on his 347. He makes over 650 to the ground before the spray, he has never had a problem driving it around town. It runs good off the line and up top.

I'm very interested in this motor? If nobody else will I'll call on this

 

[mrmustangman357]

itll do it at 9000 rpm i bet with a .900 lift cam and yates heads

 

[57fairlane]

Its already been addressed:

Go through the carb before you install it to make sure.

650 race demon, ported victor jrs, super victor intake, 393w, c4 with a TCI streetfighter converter.
6.12 @ 112 on the motor.
5.70s @ 122 on 250

 

[fastcoupe68]

itll do it at 9000 rpm i bet with a .900 lift cam and yates heads

With a heck of alot more carb then a 650cfm demon

 

[mrmustangman357]

i plugged it in dynosim, with a 650 on a tunnel ram and yates heads (estimating lift numbers) and stepped race headewrs and a .744 lift solid roller, it'll lay down 834 at 8000 rpm. so yes it can be done. streetable, not quite

back on topic, I'll keep my eyes peeled for a 650 mech secondary carb, but I keep hearing from people that vacuum sec are the way to go on a street motor. we'll see what turns up

 

[bnickel]

i plugged it in dynosim, with a 650 on a tunnel ram and yates heads (estimating lift numbers) and stepped race headewrs and a .744 lift solid roller, it'll lay down 834 at 8000 rpm. so yes it can be done. streetable, not quite

back on topic, I'll keep my eyes peeled for a 650 mech secondary carb, but I keep hearing from people that vacuum sec are the way to go on a street motor. we'll see what turns up

it depends on what trans you're running. if you have an auto trans use the vac. secondary. if you have a manual trans i'd use the mech secondary carb unless you have a really mild motor