Mustang605

iTrader: (13)

I have a stock bottom end ls1 with a big cam 242@50 & 636@600 with cnc ported 5.3 heads that flow like 317@600 with a victor jr & a mighty demon 850 race carb & its rich maybe a need to jet it down or do you believe it needs a 750 instead?

pontiac 2+2

First off, you need to R&R the engine into a chevy body! No, just kidding. Sounds like you are over carbed, I would definately try a 750. You will probably like that setup better. Good luck!!!

ZONES89RS

iTrader: (25)

750 for the street, 850 would still work good though.

wht97ws6ta

Manifold vacuum is a good indication of what the engine is asking for as far as carb. If the engine is pulling over 1.5 inches at WO throttle its a good possibility it might like more depending on how you are using the engine. My guess is that it wont see that level of vacuum on an 850 if u arent turning more than 7000 RPM. The 750 might see that much but it might give you better drivability in the lower R's.

Red94SS

iTrader: (2)

850 all the way. Just take a little time and tune it in correctly. I have a 950hp on a LS1 on the street and it runs better and is more responsive than the 750 demon I had on it.

cody161

iTrader: (18)

A Holley 950HP actually flows close to 830 CFM. What is your max RPM going to be, what is the stall speed on the car, what does the car weigh?

Mustang605

iTrader: (13)

my car is around 3000 with me in it maybe 2900 turning close to 7000 rpm & 4000 stall

brngrhd

tune the 850 with those specs.....

cody161

iTrader: (18)

With the car being that light, high stall, and 7000 RPM I would stay with the 850 and work on tuning it. The 750 would have better acceleratoin but fall off a little on top end. Once again I feel that with all of your information you provided you will be ok with the 850.

Luke_PCScarbs

What gear? The 850 should work well, but not so much a fan of the Barry Grant stuff.

Mustang605

iTrader: (13)

3.55's @ the moment but maybe 3.73's or 4.10's next

NemeSS

iTrader: (127)

i have for sale a 750HP series carb if youre interested. just used to break in engine.

3pedals

iTrader: (3)

I run a 850 mighty demon on my low compression 6.0, I like it, just spend the time to tune it PROPERLY, and you'll be happy.

speedtigger

iTrader: (16)

Interesting dyno test where they try all the popular holley sizes

http://www.superchevy.com/technical/...ght/index.html

brngrhd

so pretty much as long as you can get it to tune there is no such thing as to big of a carb.......

Luke_PCScarbs

on a dyno.

speedtigger

iTrader: (16)

I actually got opposite from the article. I noticed that there wasn't much peak power sacrifice in the smaller carburetors on motors in this horsepower range. I can tell you from experience that too large of a carburetor can be very problematic in the real world.

3pedals

iTrader: (3)

Get the big carb tuned right, and you will be rewarded with more power than the small carb, with no trade offs.
Remember, these Ls motors breathe pretty heavy for little motors, they like lots of flow. If you Choke it with a restrictive induction setup, you can kiss the power potential goodbye. Dont close your mind and treat it like an old small block, or you'll be doomed to make the same power as that old smallblock.

speedtigger

iTrader: (16)

I am looking forward to testing this theory on my car. I have a 650 DP right now and was going to try a new 750 Hp series after it was all dialed in to see the difference.

Have you actually done back to back testing on this 3pedals?

3pedals

iTrader: (3)

Well, I am looking at a 1090 King demon to try next.......