Carb size?

[Nailhead]

I've got a 496 BBC with a 6-71. How do I determine what carbs to use? The engine has rec. port 990 heads & a cam with 590 lift if that helps any. Its in a v-drive cruiser. Thanks for any help that I can get.

[FLATMVN]

I've got a 496 BBC with a 6-71. How do I determine what carbs to use? The engine has rec. port 990 heads & a cam with 590 lift if that helps any. Its in a v-drive cruiser. Thanks for any help that I can get.
If you give me you MAX RPM's and MAX BOOST I have a formula loaded in my puter and I can insert you numbers and tell you exactly what CFM you need.

[Nailhead]

Thanks guys, the engine has 660's on it right now. I havent used the boat yet, picking it up Thrusday. The carbs do seem to be too small for what it is. I'll check the pullies to try and figure out boost but RPM is gonna have to wait. I do have a set of 750's I can put on it.

[FLATMVN]

Thanks guys, the engine has 660's on it right now. I havent used the boat yet, picking it up Thrusday. The carbs do seem to be too small for what it is. I'll check the pullies to try and figure out boost but RPM is gonna have to wait. I do have a set of 750's I can put on it.
I am running a 454 with a 671 at 12lbs boost at 6500 rpms and I have 850's on it. That works out to needing 1580 cfm's of carb's so I have more carb than I need.
I used the same numbers of my motor, but inserted your cubic inches and it works out that you would need 1700 CFM'S total of carb. If you drop the MAX RPM"S to 5000 you can run 1300 total CFM. If you lower the MAX boost to 10 lbs you still need 1300 CFM. So I would say you can run the 750's with the proper jettin also. if you still want to give me your exact numbers I will let you know the out come.

[ELIMINAT THIS]

If you give me you MAX RPM's and MAX BOOST I have a formula loaded in my puter and I can insert you numbers and tell you exactly what CFM you need.
Can you run mine. 515ci ,6000 rpm,6lbs of boost on pump gas 10lbs on race gas :) Thks

[Nailhead]

I am running a 454 with a 671 at 12lbs boost at 6500 rpms and I have 850's on it. That works out to needing 1580 cfm's of carb's so I have more carb than I need.
I used the same numbers of my motor, but inserted your cubic inches and it works out that you would need 1700 CFM'S total of carb. If you drop the MAX RPM"S to 5000 you can run 1300 total CFM. If you lower the MAX boost to 10 lbs you still need 1300 CFM. So I would say you can run the 750's with the proper jettin also. if you still want to give me your exact numbers I will let you know the out come.
Thanks FLATMVN, I'll get back with this in a few days.

[Hallett]

Thanks guys, the engine has 660's on it right now. I havent used the boat yet, picking it up Thrusday. The carbs do seem to be too small for what it is. I'll check the pullies to try and figure out boost but RPM is gonna have to wait. I do have a set of 750's I can put on it.
I would not run the 660s on a blower motor they are used moor for drag racing. my 02 worth. but what do i know. :rollside:

[FLATMVN]

Can you run mine. 515ci ,6000 rpm,6lbs of boost on pump gas 10lbs on race gas :) Thks
According to the formula and your info you need a total of 1260 CFM'S for 6lbs on pump gas and 1500 CFM at 10lbs on race fuel. So if you were thinking of running 750's, it will work for the pump gas but you are at the limmit on the race gas at 10 lbs.

[Nailhead]

I would not run the 660s on a blower motor they are used moor for drag racing. my 02 worth. but what do i know. :rollside:
Thanks HALLETT every 02 cents helps. I've never seen carbs that small on a blower motor. I planned on using the 750's before i ran it unless it needs something bigger.

[Animal Magnatism]

Hey FLATMVN, just out of interest can you run mine? 565ci 15lbs 6000 rpm.
Thanks.
Paul.

[FLATMVN]

Hey FLATMVN, just out of interest can you run mine? 565ci 15lbs 6000 rpm.
Thanks.
Paul.
Paul for your specs it works out to 1981 CFM round that up to 2000 and you should be fine.
Louis.

[Liberator TJ1984]

Dual Carbs are recommended for most blower applications. Choosing the correct size carb is essential for the proper operation of the blown motor. The following formula below will help you determine the correct size Carbs for any blown application.
[(DxR)/3456] x [(B/14.7)+1]=C
D = Cubic inch displacement of the motor
R = Maximum engine RPM
B = Maximum blower boost
C = Maximum CFM required
I will throw in my 2* here also wanted or not :p
It is very hard to "Over Carb " a blower motor as long as it is jetted correctly,
I am running 2-1050's on a stock bore 454 and mild cam.
My buddies are running a Hat on a 509 in their Pro-Mod that is capable of flowing over 4000cfm ....it's all in the tune up from what I've seen ?
Maybe one of the Pros can add to this idea of mine ? :)

[bigkatboat]

I feel that Liberator is very close in his thoughts. I have found that very mild (5/7lbs) blowers need close carb sizing, but it is mostly for transition at lower RPMs. You don't want too much vacuum at the carb bases at WOT, so you go to larger carbs. A blower (any blower) won't make boost (no matter how fast you turn it) if the 'hole in the top is too small'. If you have a mild setup and large carbs, it will bog or backfire no matter what the jetting. In the other direction, I've used a 3300CFM hat on a 14-71, 468" 454 Chevy with Chevy Brodix heads. The motor saw 21lbs and the big ol' flat boat ran 135 + MPH @ 8300 with 32's. No 'flat spots' With carbs remember the needles and seats will only flow 'so much' fuel, so always use the largest size you can get.

[acatitude]

Can you run mine. 515ci ,6000 rpm,6lbs of boost on pump gas 10lbs on race gas :) Thks
Kaler Ive got a set of nickerson 850"s flowed at 920 if your interested.
and for anyone else I have a pyramid type race manifold off my reg deck 540 and a bowtie gmc block standard bore 4.50
$1200.00 for both carbs
$1000.00 for the bare 540 bowtie gmc block
$250.00 for manifold

[pebo]

Nailhead, what are your plans for the 660's ?

[Nailhead]

Nailhead, what are your plans for the 660's ?
Not sure yet. I'll know more in the next couple of weeks. Just fired the motor about 1/2 hour ago for the 1st time. I'll PM you with my plans for them.

[kaqster]

I use that same basic setup as you and use 2 825 CFM Race Demon Blower carbs with a replaceable venturi sleeve. I could go out to 900 some with the next bigger sleeve so there is room to grow if you up that engine more with different heads, cam, etc.. Works ok so far.

[thiggy]

i have 2 750 hp not blower carbs do the need to be thanx

[Liberator TJ1984]

I would think you would be OK if you set them up right ??
My Dominators are not " Blower Carbs " or boost referenced

[Dimarco Kid]

I got a question for this thread....my mill started out as a Mike Kuhl "River Rat" engine. 454, all steel bla bla bla....came with 1050's from Mike. Now it's a 490 ported 990's (same heads) bla bla bla...and alot of guys are telling me my carbs are too big! I'm "de-tuning" it a bit for my jet (came out of my hydro) and have always had EXCELLENT luck with the Doms. Probably won't change them ($ issues), but wouldn't Kuhl know what works well? And everyone else says "DOMINATORS!!!!, MAN....they're too big for THAT motor!!!!"

[Liberator TJ1984]

Dimarco , I went thru the same crap :rolleyes:
awww yer crazy , no way that will work.....
well it does and Very Well ...basicly here is what I got...
454 std. 8.75/1
320 119cc alum.heads
620 lift roller 236* dur.
8/71 > 2/ 1050 Doms. w/ 92jets squared @ 15%over on gas
Plugs are a perfect tan ( NGK's) # 8's I think
all my engine builder told me is when you start rammin' in all that air ...You better be able to deliver the gas to match....
It may not have worked for others ,but seems to be perfect for me :cool:

[Dimarco Kid]

LOL!!! I got 92's in mine too!!! Hahahaha
My heads flowed 317cc's after port work. Big cam tho....727 lift. Going back down to the mid .600's for my jet. Carbs are inline on a Kuhl top mount. Work perfectly. Shouldn't mess with it anyways...just curious why people think it's "crazy"!!!!
P.S. I think Charlie Daniels is the shit!
"pour me another one, I'm finished with the other one, I'm drinking my baby GOODBYE!!!"

[Liberator TJ1984]

Right on ! thats what I had to work with so we gave them a shot anyway , lookin' back I would cry if I bought a smaller set of carbs to find out later these would have worked . I could have ran a set of 850's I was Borrowing from BlownGas ,they worked really good ,but as we got up into the bigger jets to richen it up , we were like...what the hell ...slap the Dominators on there and see what happens ? .......Bingo !!! we got a winner !!! :idea:
ps..they are the "new style" carbs so maybe they have different circuits inside that allow them to work....over the old style bodies????

[Dimarco Kid]

Mine are the "old" style. Original from Kuhl. Thing is....they work, already have the top mount, linkage, and that big beautiful scoop made to fit, and they work!!! So, they're staying on. Can I ask what numbers you run? Did you have your mill dynoed? I'm putting this in my jet (lightweight "v") and it came out of my hydro. Flat ass screamed in the hydro, can't say numbers cuz loosers without boats come outah the walls to say I'm full of shit, but you know what it would do. Just curious to see what your combo runs!

[Liberator TJ1984]

Only ran once last year at Marble Falls Tx.
so no previous race experiences , no prior fine tuning of rideplate ,shoe , nozzles etc...straight from the lake to the put in ramp....
600# hull with sterio ,etc...only removed back seat for rope defletor install,
best was a 10.98 @ 99mph ...started to get the hang of things and would have done better if had more experience :rolleyes: but had a blast anyways ,at least when someone rags me at the lake I can say ...heres my timeslips wheres yours ..put up or shut up :p

[Animal Magnatism]

Hey guys, I'm running two 1150's with 98 jets on a 565 / 1071 setup. Plugs are spot on. I'll be checking with an O2 meter shortly, just to confirm.
Paul

[Dimarco Kid]

Only ran once last year at Marble Falls Tx.
so no previous race experiences , no prior fine tuning of rideplate ,shoe , nozzles etc...straight from the lake to the put in ramp....
600# hull with sterio ,etc...only removed back seat for rope defletor install,
best was a 10.98 @ 99mph ...started to get the hang of things and would have done better if had more experience :rolleyes: but had a blast anyways ,at least when someone rags me at the lake I can say ...heres my timeslips wheres yours ..put up or shut up :p
Nice...I was hoping for mid 90's from mine. Cross my fingers.

[Liberator TJ1984]

Just drop the Snowmobile motor in :crossx:

[Dimarco Kid]

You wants specs on the sled motor? It's ridiculous!!! Dad's money pulling though for me!
Arctic Cat 1465cc triple cylinder, 18.2 to 1 turns 10800rpm and made 300+ in the heat of the summer. Just put a "Boondocker" nitrous kit on and pulled 378hp @ 11200 in 70 degrees. Sled weighs 428 lbs without my ass on it. We shooting for the 7's this year. I've seriously got MORE money in that triple than I do my blown 490!!! Ok...let me refraise...DAD'S got more money invested than I do in my boat motor!!! LOL

[Liberator TJ1984]

A little more Cash and you might get down to a side by side pass against Force :p
Have you thought about getting into the Hydrophonics business ?? It worked for those guys in Tennessee :crossx: at least till they got caught....

[Dimarco Kid]

Back before I became a cop, my girl had a Dodge R/T durango that we pulled my hydro with. I went and got vanity plates for it that said HYDRO, rumors started after that!!!!

[Liberator TJ1984]

what hull configuration are you running ?

[Dimarco Kid]

My old boat was a dimarco hydro. New one is a lightweight southwind v. Hoping that I can get it into the mid 90's with this blown 490. What hull do you have? Tunnel right?

[thiggy]

ok i told u all that i had a 468 ,671 dyers blower rr brodix heads 2 750 hp racing carbs that came with 73 f 73 b with 6.5 p v f/b do i try those jets that r in it, or re jet carbs.they r not blower carbs and i wont be racing it but would like the best performance thanx

[Dimarco Kid]

It's hard to tell from my point. I run at sea level and cold all the dam time, run mine really fat. I would fatten your 750's up tho...alot. I always run fat then go down. I'd rather have shit on my back deck than aluminum on my plugs. Who knows...someone might pipe up and say i run those jets just fine. Everyones different, that's why I asked about my 1050's. But my opinion is fatten it first. Good luck!

[Liberator TJ1984]

DK,
1984 Lberator Picklefork 19' 600# hull , Dominator pump>A+ SS impeller