After failing with the HSR I want to try a carb out to check if the shortblock is okay and see if all my problems lie in the EFI. I have an old Performer intake to try out and see if the shortblock is good before I buy my Performer RPM Air-Gap.

I'm new to carbs and want something that won't give me more headaches I won't be able to figure out. I've done a ton of

I'm looking into a Speed Demon 850...great price, amazing looks, and POSSIBLY great performance. This unit is rebuilt with a factory warranty.

Will this be too much for a 10.1 CR 383 with Trickflow 23 Degree heads and Eventully the RPM Air-Gap? Cam is Hyd. Roller 230/236 .510 .520 plus 1.6roller rockers.
I've done some VE calculations that say it is but searched and got mixed opinions. I'd like to be able to have the option of upgrading (turbo?) in the future.

 

Should be about the right size. It'll probably be a little lame with the Performer, but will wake up with the RPM.

 

I'm inclined to think it's too big; might be OK with the Performer, but will be too large on an intake with some plenum to it.

BG rates their carb flow differently from others; their way gives about 20-35 CFM less than using Holley or Edelbrock's methods. In other words, that 850 would be "rated" as 875 or 880 if it was a Holley.

If you get a vac sec one, the secondaries will NEVER open fully, with that little small block under it.

I think you'd get a better all-around match with their 750. You can call them and ask, might be wise to do that before leaping.

 

skip BG crap.

go holley hp 750 or the proform 750. I have the proform 750 in my camaro and am VERY happy with it. Now go search on here for all the BG stuff that has aluminum shavings in it blocking passages from the factory out of the box.

 

I have read about BG's QC issues but these are rebuilt units off eBay with the warranty making me think its their attempt to fix them...they just look so good too! $450 shipped for the Speed Demon 850 with the line kit and a fuel gauge. The 750's are the same or even more!!!

If everything turns out okay I will move to the Air Gap RPM, this Performer is just a trial thing to see if the shortblock is good to go (I built it...). I do want to go nitrous or turbo if this turns out okay and I only want to buy the carb once. I did have a slight inclination the bigger plenum might cause problems with the RPM but hopefully I will have the knowledge then and can tune out of it.

I am defenitly sticking with mech secondaries and no choke since this is a weekend cruiser.

I am also moving away from Holley or Proform because their compatible 850 is about $200 more...If I come to find out the shortblock is screwed I'd rather have that $200 in my pocket.

I did just buy a cheapo $50 HEI dizzy off eBay...hence I'm trying to do this trial cheaply but don't want to buy things twice.


BTW...if this shortblock does turn out to be unuseable I'll be looking for an assembled shortblock. I'd rather have the stroker but if it comes to it I would go with a 5.7L. (But I'm not giving up on my first successful motor build!) Where can an assembled shortblock be found?

 

I'm going to say it might be too big. I tried out an 850 on my 350 when everyone was telling me to and it was just waaaaaay too much. Driveability went down the crapper. Stuck on a 750 again and the car runs great.

 

annular boosters would make that 850 seem like a 750 on the street.. your average power will be much more but your peak will fall just a tad.. thats why i went with the annular 750 mighty demon..

 

I might be able to make the 850 work but I know I really should go with the 750. The eBay store only has the Speed Demon 750's with vacuum secondaries and I want a doublepumper....

 

you will have a field day tryin to make that 850 work right.. your combo is just not wild enough to need an 850.. i know your tryin to plan ahead and save money for the future turbo, but will it be worth the headaches that the 850 will bring now?

i mean jeez, there was a guy runnin 10's with a 383 and a 750 mighty demon.. he estimated around 550hp..

 

Yea I've decided to go with a Speed Demon 750 Double Pumper. The carb has been rebuilt but has Demon's warranty, a fuel line kit and gauge, carb studs, and the tuning DVD.

I don't know why I'm so hung up on Demon's but I want one badly!


Are there compatible Holley 750's for around $400-$420???

 

Okay...Holley HP or Speed Demon???? The Speed Demon has the line kit and gauge....

 

I didn't have a problem with my old Speed Demon 750 and the Mighty Demon 750 I have now seems to be even better. These were both older models while the Mighty 850 was new, it had chips inside the bowls and metal flashing covering some of the holes a little bit.

 

you will be happy with the demon.. since its reman'd.. for some reason, out of the factory, they are crap.. my mighty demon had jets that were 18 sizes too large!!! i thought they gave me an 850.. but reman carbs are good since they clean it out and replace junk parts and what not..

 

Well, I think I'll stick with the Demon then. I know the Holley HP is a good carb and would be a good choice but I'm leaning towards the Demon for soem reason.

 

proform 750.