http://bbs.off-road.com/wwwthreads//...collapsed&sb=5
I don't know how exactly related our tbi CFM rating is to a carb CFM but this low CFM carb Jeep makes LS1 power!

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

 

you don't need a lot of cfm if you chose to follow the air velocity theory of induction. you are however always limited by the total amount of air once you have gone too far.

later
tim

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91 Camaro RS-LO3,Auto
New Times Coming Soon!
Check Out The East Coast F-Body Nationals Home Page
www.geocities.com/njspeeder
My MAFB.ORG Home Page
www.mycar.net/mafb/registry/detail.cfm?id=299
DSI Racing Home Page
www.geocities.com/foff667

 

I can agree with that because I had the 670 and the stock TBI unit on the 350 that I just took out of my car and I could tell no differance between the two except that it seemed to run better (smoother) with the stock unit with 55lb injectors. I cannot see needing a larger than stock TBI unit on a 305 unless it is really built up. I might put my Vortec heads, intake and LT4 cam on my LO3 to see the results on a motor that I have been driving for several years with the same mods.

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91 RS 5.0 TBI....Edel. TES headers .. 3" exhaust ..... 5spd 3.08

 

if it aint broke, dont fix it. if you dont NEED more cfm, than you dont need more.

 

one of these days you guys will figure it out.

 

All I gotta say is NASCAR!
Do a search on the power:cfm rating and you think that jeep is good, haha.
BTW, cfm on a carb is a LOT different than on a TBI or TPI intake. The carb needs the air velocity to atomize the fuel better. If you have a huge carb on a small engine you can probably adjust for it BUT you won't make any more hp than with the least you can get away with. With EFI it doesn't matter how you meter the air just as long as you do. The smaller TB limits the air so your engine WILL feel smoother. The problem with huge TB units is the pump shot (aka acc. shot). When you snap open the blades on a large TB you will have an even larger pressure increase and the fuel will collect onto the sidewalls of our wetflow systems. You can probably install a 2" unit on any size engine if you just adjust for it in the eprom (aka chip). This is why eprom burning is so important because I don't think I've ever heard of a carb being tuned with just fuel pressure!

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, Jon (350 TBI!)
91 Red My website

 

http://www.rpmeng.com/rpmpic.htm


then page down to the 525hp 390cfm engine...

390cfm carb making 525 hp... please believe. subtract 200hp and believe, for crying out loud. Happens every day.

A Recon 377cid with 600cfm holley makes more than 370hp EASY...


[This message has been edited by fast_broker (edited September 23, 2001).]

 

They didn't mention what c/r that engine was using. I bet it was above 12.5/1 Probably closer to 14.0/1. Just thought a I'd throw that in.

 

Too small of a carb on a motor does the opposite that a supercharger does. It lowers the pressure in the intake. When a motor is seeing vacuum at WOT power is being limited proportional to the ammount of vacuum. The real question that remains unanswere is: Are these low CFM motors seeing pressures in the intake that are lower than atmospheric? If they are they are loosing power.

 

It couldn't have made the CR any clearer!!! It states "9:1 Southwest tour/ASA Engine" in big/bold font.

ALL ASA enignes are 9:1/360cid max/390cfm Holley carb. Southwest is 410cid max, I think... Rules is rules. I am sure that the vac level in the intake of that motor could pull your teeth out if you put a vac hose in your mouth but just proving a point.

Probably get another 100+hp with a bigger carb, for sure, but those combos are developed to run with substantial vac present. I sometimes put a 390cfm on new motors for break-in. Run quite nice, actually, with TONS of throttle response.

[This message has been edited by fast_broker (edited September 24, 2001).]

 

tbi and a carb need to be treated to the same engine theory since they both rely on the manifold to atomize and mix the air/fuel. the key with any small cfm application is to control the levels between initial velocities and "run" velocities. if the cam is correct for the application the a/f velocity to rpm relationship in the manifold will be the same as soon as you crack the throttle at 1Krpm as it is when you have your foot on the floor and the car is at 6Krpm.
thesee types of motrs are a balancing act once you get to the types of power numbers being discussed here. that is why most people have been brainwashed with the total volume theory of hp. it is just easier and usually makes for far more streetable applications, ie: smoother idle, more vacuum at idle, better emissions......ect.

later
tim

------------------
91 Camaro RS-LO3,Auto
New Times Coming Soon!
Check Out The East Coast F-Body Nationals Home Page
www.geocities.com/njspeeder
My MAFB.ORG Home Page
www.mycar.net/mafb/registry/detail.cfm?id=299
DSI Racing Home Page
www.geocities.com/foff667

 

fast-broker I think I need to have my perscription renewed. I missed it altogether. That is impressive.