JesasaurusRex

iTrader: (3)

Well fellas, tryin to finish up this build and top her off with a carb.

412 SBC (.030 over and a 3.8" stroke crank)
Super Victor Intake
AFR 220s
Solid Roller Cam 264/272 @.050, 649/649 lift, 107 LSA
11.41:1 static compression

If desktop dyno is at the least bit accurate this thing should be making max power at 6500rpm give or take a few, and should not see anything above 7000rpm.

So did the calculation for 100 percent VE for a 412ci motor that sees 7000rpm. Theoretical cfm is at like 830 something. Now seeing how theoretically even tho it should be fine with an 850cfm carb i know that a lot of times stepping it up to another size has actually proven gains. Only problem I am running into is the $ amount from stepping up from an 850-950 is a lot. You guys think this motor will be happy with an 850cfm carb or do you think i should just save up because the gains from going to a 950 carb will be worth it? Thanks fellas

fb305svs

theoretically, you only need like a 650-700....

in actuality - i'd have no qualms about putting a 850 on it....

JesasaurusRex

iTrader: (3)

...how did u do ur math? I used 100 percent VE for ****s n giggles.

IHI

iTrader: (1)

The 950hp is an overrated carb from the factory, 850 main body with 750 base plate actual wet flow 830cfm. Just be aware of that before you purchase it. It will work great for your motor no doubt, just know your not actually paying for a true 850cfm carb when your dropping $660.00-I know

That little mill out to put out some pretty impressive numbers, get a nice 55-5800 stall and some tall gears you'll be in the 10's easily on da pump gaz!!

JesasaurusRex

iTrader: (3)

Is it really? Demon wet flow their carbs? If so i guess ill get an 850 demon. I plan on usin my 3.73s (till the 10 bolt breaks ) then ill get myself a 9" and slap some 4.56s on . As for the stall speed...i gotta T-5 lol i got 2 things waiting to go . Oh well, least i can fire her up an listen 2 her now n again till i save the cash to get a better drive train. And the running on pump gas thing. Thats what i was hoping for but it doesnt look like it (unless i did my dynamic compression calculations wrong) i cam up with like 9.77 dynamic compression. Wanna double check that 4 me

JesasaurusRex

iTrader: (3)

oh cam timing abdc is 55 sorry bout that & a 6" rod

IHI

iTrader: (1)

I dont know if I'd personally run a Demon, but that's just me. The shop that built the motor in our S-10 and dynoed it was telling us all sorts of stuff and when we got onto the carb issue from the tests they've done on the dyno the said all the Demons they've tried customer brought in experienced a lean out condition during higher rpms. They said they'd be making the pull and fuel/air ratios would be perfect and when it neared the 6000rpm range the carbs would lean way out enough to make them abort the run and ask for owners permission to continue to pull past that spot. And after they surpassed a certain rpm range then the ratio would come back to normal-or where it was supposed to be.

Brother in law runs a race demon, but he does'nt make it to the track enought to go enough rounds for any definative answers to say first person if it's a problem or not, and plus the fact we're only burping these things a 1/4mi shot so it's not like it's a long duration that a round track motor would endure....but they srue are pretty

If I had more time I'd get more information from you on all the exact specs of everything to see how it comes out compression wise, but if your pretty confident it's 11.4, the aluminum heads are a shoe in for dropping one full point due to heat disapating quickly, throw in the longer duration cam that is again allowing more air to escape before both valves close up, the 6" rods with longer dwell so your timing should be reasonably lower that what a 5.7 would typically be so strictly off the hip it should'nt be a problem. I can run 92 octane all day long with no troubles at all-actually it's what I fill up with after a race weekend for tearing up the town or racing an off race/fun race when I drive to the track, but on race day I prefer 110 cuz it smells cool Just be sure to get your plugs heat range correct.

Initally I was running too cold of a plug and it would load up terribly on the street, then went to the other side of the spectrum to a very hot plug and then it dieseled after cruising when shutting the car off. My motor liked the 3rd plug from coldest for street/strip. that on the scale of the last number being 0 through 9 on the plug part number and 0 being the coldest mine liked the 3. (AR3923) Autolite race plugs. You'll probably go faster with timing in the 35-38* range, but you'll have to experiment with that as always.

The 3.73's are gonna be the weak link and probably a peice of the equation that will make you slow, if you were running a 26" tall tire that would help, but you would'nt hook with the manual and that type of power, so hopefully it blows up soon-it will and you can get it geared right for max effort and big smiles It'll be slow out of the box-that said light heartedly since it'll still be fast-just not optimized, but ought to pull real hard about 4500 on up!! Will be cool to see what you come up with after it's up and running.

JesasaurusRex

iTrader: (3)

Well over here n cali highest is 91 so im iffy on it. Ill probably do a 75/25 mix or somethin. As for the plugs, im startin with some Autolite 3910s...cuz AFR suggested it lol, well c how good a suggestion that actually is.

84firebird383

I have no personal experience with this carb yet, but its the one I want to try when I have the money. Its an AED prepped 950 HP holley they call 950MOD. Thru emails with the company they told me it flows about 875 cfm . Its the same 750 body with the 850 baseplate. They also told me that an out of the box HP 950 normally flows 810cfm. Also the price on their site isn't right. If you call them up they sell it for $679.95http://www.aedperformance.com/

IHI

iTrader: (1)

The AR3910's are what I started with also based on the AFR recommendation, but them's some cooold plugs lemme tella I dont know how crooked your parts stores are around there, but when I first started buying them (plugs) I was paying $32/set after sales tax at O'Reiley's whereI have an account set-up. Now only pay $21/set for the same brand plugs at Parts America so might wanna call around first.

Another carb shop that' is HIGHLY recommended from racers all over the country http://www.apdracing.com/dragcarbs.asp?news=1

Same deal, would call them personally to get a real price on a carb.

fb305svs

well, for carbs, we usually use a a number of around 75% eff...

i talked briefly with the chief guy at the shop today - he said a 950 wouldnt hurt anything, might even gain you a few ponies up top - but no doubt the 850 will give you better throttle response, and eliminate bog situations that the bigger carb will present... nothing that cant be tuned out though with a good amount of time...

i run an 800 (750HP with the upgraded main body) on a fairly decent cammed 350 small block - it doesn't seem to mind it.

I too would stay away from demons - we've experianced that top end lean thing with the ones we've had on the dyno as well.

if you want to take a chance, you can always try and pick up a used 850-950 holley 4150HP, and then just send it out and have it worked over, blue printed ect. for the same price of a new one, you'll have a carb that you know will be good out of the box... just another option i've seen them up there in what looks like good shape, for around 300 bucks.... to have the carb upgraded, blue printed and rebuild with all the goodies your looking at about 350 bucks... so voila, ur at the 700 mark...only better than a box stock anything..

JesasaurusRex

iTrader: (3)

Appreciate the help fellas, looks like ill be throwin an 850 on her. Now only for my pay checks to get here faster