Jetting-where to start at

i have a 393w ford that is pretty decent, , i am looking for a base starting point for jets in the carb ,timing is locked out and will try it first without a power valve, here is what i have


393 ci Windsor sbf--
ross pistons
13-1 compression
cam -solid roller -.691-692 lift Duration@.050 intake 261 exhaust 268
fully ported super victor
750 mighty demon
200+cc intake runner heads
flowed 306@.650intake --246 ex

that 750 is toooooo smalllllllll but I would put it 80-82 square and no P/V's and see what happens

950 cfm catogorie mid to high 80 jets !

2015-04-23

butterbean wrote:that 750 is toooooo smalllllllll but I would put it 80-82 square and no P/V's and see what happens

750 demon flows more then a 850 holley

johndickjr wrote:2015-04-23

butterbean wrote:that 750 is toooooo smalllllllll but I would put it 80-82 square and no P/V's and see what happens

750 demon flows more then a 850 holley

Really, how???? 750 CFM to a 850 CFM

butterbean wrote:

johndickjr wrote:2015-04-23

butterbean wrote:that 750 is toooooo smalllllllll but I would put it 80-82 square and no P/V's and see what happens

750 demon flows more then a 850 holley

Really, how????  750 CFM to a 850 CFM

every carb maker holley-aep-etc flows their carbs dry..demon flows is wet, if it was measured dry the 750 mighty demon is close 900, here is a few post on this, and even joe sherman has confirmed this

http://www.speedtalk.com/forum/viewtopic.php?p=182595

http://www.yellowbullet.com/forum/showthread.php?t=393682

johndickjr wrote:2015-04-23

butterbean wrote:that 750 is toooooo smalllllllll but I would put it 80-82 square and no P/V's and see what happens

750 demon flows more then a 850 holley

the last demon I had went strait to the junk where they belong

johndickjr wrote:
750 demon flows more then a 850 holley

Well we have one on a stock 351w and it can't feed it enough

I picked up 3 tenths on a well sorted combo with a qft 750 over a demon 750 back to back passes, and no tuning on the qft.. 11 to 1 347 ran 10.50s.. went from 10.83 to 10.57.. Gained 2 mph and a tenth in the 60ft 5000 stall.. I will never put a demon on anyting but a project on a budget that never goes to track

same deal with me, we had a 750 demon on a 406 chebby in a 80 camaro and it went 7.42 in the 1/8th on the same day we put a 750 holley DP on it and it went 7.17 with in 1 hour of each pass so don't believe everything you read on the net!!!!!!!

i have never had any issues with a demon,  , i had a brand new 750 Dp holley on my falcon, did ever thing under the sun to and it was never right, put the demon i have on it and was near prefect , i like them, and i have what i have, you buy me a new carb and ill use what ever you want..lol, it has to work for now till i get my new prosystem carb, either e85 or alcohol , not sure yet

noslo533 wrote:I picked up 3 tenths on a well sorted combo with a qft 750 over a demon 750 back to back passes, and no tuning on the qft.. 11 to 1 347 ran 10.50s.. went from 10.83 to 10.57.. Gained 2 mph and a tenth in the 60ft  5000 stall.. I will never put a demon on anyting but a project on a budget that never goes to track

If you picked up 3 tenths with just a carburetor swap then you didn't have a very well sorted combo.

DaveMcLain wrote:

noslo533 wrote:I picked up 3 tenths on a well sorted combo with a qft 750 over a demon 750 back to back passes, and no tuning on the qft.. 11 to 1 347 ran 10.50s.. went from 10.83 to 10.57.. Gained 2 mph and a tenth in the 60ft  5000 stall.. I will never put a demon on anyting but a project on a budget that never goes to track

If you picked up 3 tenths with just a carburetor swap then you didn't have a very well sorted combo.

I agree with you.... But their where a bunch of junk demon carbs built by Bg back in the day.... Everything from improperly drilled blocks to metal shavings in them. Ask me how I know.

dfree383 wrote:

DaveMcLain wrote:

noslo533 wrote:I picked up 3 tenths on a well sorted combo with a qft 750 over a demon 750 back to back passes, and no tuning on the qft.. 11 to 1 347 ran 10.50s.. went from 10.83 to 10.57.. Gained 2 mph and a tenth in the 60ft  5000 stall.. I will never put a demon on anyting but a project on a budget that never goes to track

If you picked up 3 tenths with just a carburetor swap then you didn't have a very well sorted combo.

I agree with you.... But their where a bunch of junk demon carbs built by Bg back in the day.... Everything from improperly drilled blocks to metal shavings in them. Ask me how I know.

Tell me about it! Earlier this week I had a customer bring in a big Chevy to run on the dyno with an 871 and two Demons which needed to be rebuilt. I took them apart and went through them and while doing so I noticed that besides some awful boosters in both bodies one body had never been drilled through to allow manifold vacuum to actuate the power valve! The holes were started but not drilled through all the way. I was told that this is not uncommon on these carburetors.

If you guys looked at the specs on Demon carbs you would wonder how they ever ran properly.
Some are really screwed up.

http://www.demonfuelsystems.com/Tech/Identification.asp