southernsmoker

Back in the spring I came across a great deal on a low mile LQ9 and bought it. I have just started building the motor and need advice on sizing for the carb. This will be a stock engine with untouched 317 heads. I have a Vic Jr to go on it with plans of running 1-7/8" long tubes. The cam has been cut and is as follows:
Dur @ .050 235/242 .620/.593 109+2. This will be put in a 3500-4000lb vehicle for mostly strip use. I intend to spray it between 150-175 shot. My intent is to eventually bolt on some better heads. My question now is will a 850cfm carb be too much for now? After reading articles all day on here and in other magazines about carb sizing I really want opinions from guys that have done this already. I see a lot of members running both 750 and 850 cfm with great results depending on application. For all out HP and using the bottle, I would like to go with the 850 for high end flow but I don't want to waste what little money I have on the wrong carb. I know a lot depends on tuning. Also, is it worth getting annular or stick with down leg? Will the downleg 850 be to much carb compared to the lower flowing annular? Thanks for the help!

speedtigger

iTrader: (16)

How much torque converter?

southernsmoker

Stall will be around 3800 to 4200. Im afraid it will be on the street more than it needs to be. I may not be able to get away with stall that low. Just gonna have to see. Btw, my track is 1/8th mile so it will be a deep gear for the rear also.

fast89stang

iTrader: (2)

I got a 950, but my car is only right at 3k, my track is 1/8 mile also, but i only choose to run 4.10s. But i wanted to buy a carb once, and I love my ultra 950 hp. It has taken some work, and still is, but it is a bad *** carb.

speedtigger

iTrader: (16)

With that much converter you could run either one.

onefast84

I would go with at least an 850 in not a true 950 if you plan on putting heads on it in the future.

3pedals

iTrader: (3)

Carb size is a confusing topic for sure. You can't go wrong with the classic 750 holley. When you start wanting more is when it gets confusing.
Holley rates there carbs at least 2 different ways and other carb manufacturers rate theirs different than holley does.
Example -Demon carbs , 750 demon flows way more than a 750 holley, as does any demon, # for #.
Holley 950 actually flows less than a holley 850!
Do your research folks!

fast89stang

iTrader: (2)

Except the new Holley ultra 950 hp. Its suppose to be a true 950

huggerorange69

iTrader: (7)

I have a quick fuel 850 on a lq4 with 317's that have lots of work done to them, 3500 stall converter with a glide, 4:86 gears, it kills the plugs easy, always seems rich, its been re-jetted abunch, I would recommend a good ole holley 750 double pumper

3pedals

iTrader: (3)

cool, did they up the venturi size?

I really liked the mighty demon 850 I ran when n/a, but it was on the verge of too big for sure.
If I run another n/a setup it will most likely use a 750 mighty demon if I can find one.
I like the Demons if you havent guesed! lol

windmill

iTrader: (4)

the diff is demon's is wet flowed, other is dry,,, that's why when you get a 950 hp they flow it for your car more,,, where demons is dead on,,,
also my 950 hp e85 is only flowed at 926 I have the flow sheet.

fast89stang

iTrader: (2)

Yes 3pedals, they upped the venturi size to 1.600 I believe. I think thats why it needs so much jet, it flows so much air. I dunno. I know I was told to block some emulsion bleed holes in it, and change the size of them, but it hated that. It only ran 6.59 that way with like a 1.46 60ft. I put them back stock. I want to find a way to downsize the main air bleeds or something so it will pull more thru the jet and I can jet down. Most carb people want me to change the emulsion bleeds again, and I hate to since I have it so close. One I get my jet sizes right, i am gonna try and put a front power valve in it to clean it up a little. I feel like there is a little more left in it.
I plan on taking the heads off this winter and putting some thinner head gaskets on and cleaning up the ports a little. I may throw in some rod bolts too, just to feel safe. I am hoping it will at least run 6.20s in the heat.

Doug G

Was told the same thing from a Demon Tech.
A 750 MightyDemon on a Holley flow bench would flow in the 930cfm range . This is why so many had issues with Demons.... they bought a Demon the size of their old Holley and it flowed too much causing issues and the carb was blamed.

JRracing

iTrader: (35)

I have a qft 950 that flows 1100 cfm. I thought that would be to much for my 383 ci motor but it runs very well.It is a annular carb. Custom built for my motor by a carb distributor on ebay.

I can tell you that a spec built carb for your motor will flat smoke a off the shelf carb or one you got from a buddy or something else like that.
I went from a off the shelf demon 750 to a custom built 850 and it picked up almost two tenths. Luckily, I didn't buy the demon, it came with the car when I bought it.

speedtigger

iTrader: (16)

So you are saying that you have a 4150 based carb with annular boosters that flows 1100 CFM? I would like to see this carb as I do not think that is possible.