Picking Carb Size: 950, 1000, or 1050 CFM?

Which Quickfuel Carb?

  • QFT 950

    Votes: 4 50.0%

  • QFT 1000

    Votes: 1 12.5%

  • QFT 1050

    Votes: 1 12.5%

  • Other (In comments)

    Votes: 2 25.0%
  • Total voters
    8
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yellow rose said:
That's why I said not to chose a carb by CFM and pick it on venturi size. You can use a 1.410 Venturi with an 850 base plate (1.750 throttle bores) and easily get 950 performance with 750 bottom end.
You can get a BLP BX4 for $850.00 and that gets you billet main body, base plate, metering blocks and and all the adjustablity you could want plus a BLP tune up.

For the money, it's probably the best deal going out there.
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Wait a minute? You mean carburetor technology has evolved and improved since the 1960's? Can't be...
 
@273

WHat cfm calc did you use?
How is the calculation made?
 
AJ/FormS said:
4.88s for street?
Hah, I tried that,and, IMO,it sucked.Sure 7200 got me 100kph/62mph at the top of second.
But cruising 62@3760, well,IMO that's crazy.And with street suspension and 325/50-15DRs,my little 360 didn't stop spinning at the track all the way thru the 1/8th ending at 93 mph! and that with a 750DP. My conclusion was 4.88s suck. But if you like 'em so much, I have two sets I can sell you.
So then I installed 3.55,which still spin all the way past 93 mph, but now I can cruise at 2734, over 1000 rpm lower.
4.88s allow for 7200@119mph in 4th gear.
BTW
OP said"not frequently"
4.88s are very low gears for the race track. Most guys with big power will be running 4.30s
4.10s are very low gears for the street.On the street with big power, any old gear in the 3s will do, with 3.55s being middle of the road.
>OPs BB in a 67/69 Dart will be down at under 6pounds per horsepower. Good luck making that stick on the street below the speed limit,with any tire that fits in the stock tubs. It's hard enough at 9 or 8 #/hp
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So are 4.56's too low for the street? I don't want to do it wrong.

It's incredible to say a 4.88 is too low for a race car. Ever watch Comp eliminator? You can't make a blanket statement like that.

The gear you need is the gear you need. I realize that my generation was the first to think a jap car and a fart can was a hot rod, and that anything over a 3.23 gear is too low for the street. If you don't like the RPM, unhook the tach.
 
YR - AJ thinks 4.88's for the street suck.
 
273 said:
This a great misunderstanding of carb sizes.
Basically no matter what carb you run on your engine it's gonna be the same cfm in your case about 911 cfm just at a different vacuum level.
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Correct. The larger the throat, the less the vacuum and the more prevalent the off idle stumble becomes.
 
Well car has a 8.75" sure-grip rear with 5.13 gears and 31x18.5R15 tires with 15x15" Centerline Auto Drags.
 
rumblefish360 said:
AJ, you needed a better tire and suspension.
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Yeah, I know, but this is just way too much fun
I tried the SS springs, and they're not going back on. I tried the adjustable snubber, and it's not going back on either. I tried a second mainleaf,eye to eye, and another shorter one for good measure and I clamped the whole works,and installed some heavy-duty 3-way rear shocks, which sorta worked, but the clamps had to come off.
So now I have rear-steer, adjustable by throttle, and I am having a blast.
But it's just a 367, not like a BB with a 252/260/110@050 cam,lol. So if I can spin 325/50-15 DRs to 65 plus mph, imagine if I had 150 more hp.....
 
ToMang07 said:
Well car has a 8.75" sure-grip rear with 5.13 gears and 31x18.5R15 tires with 15x15" Centerline Auto Drags.
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Now we're getting to the meat and potatoes.
Your 5.13s and 31s are the equivalent of 3.97s corrected to a 24 inch tire.
In my example above with the 4.10s with 27 inch tires; these equate to 3.64s
With a 2.66 low gear, the TM will be 10.56 for the 5.13s and 9.68 with the 4.10s. this is a difference of just 9.9%.
In my FormulaS combo I run the equivalent of 9.75TM in first gear.

So while you have 5.13s (a very low number), the fact is that it is just on the big side of street fun. But now if you feather it out at 250 ftlbs at 2000 say, then if you multiply that by the starter gear of 10.56, then that comes out to 2640 to the pavement. Those tires may actually hook at those numbers, But if you floor it,in about 2 seconds your engine is gonna be up on the pipe, and then some 5000ftlbs may be coming down the axles, and you will be doing just 30 mph. And I doubt those tires ever stand a chance.
Let's say those tires put a patch onto the pavement that is 240 total sq inches. That would be somewhere around 21ftlbs/inchSq,@30mph
I have put 3800 ftlbs into a pair of 90" BFG-DR patchs.This is about 21ftlbs/inchSq @30 mph. And tirespin.
So currently I put about 2600 into a pair of 60"patchs(BFG/Cooper 295s), @45mph,with predictable results,tirespin. This is also about 21 ftlbs/inchSq.
 
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273 said:
Not sure what the question is ?

For the 911 cfm I use cid x rpm/3456
But that's how much cfm an engine uses not carb size.
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1 answer did both questions!
Hip check and a score!
Thank you!
 
I like big carburetors, you just have to tune them. Holley's 950HP carbs don't flow 950 cfm, all they are is a 850 base plate with a 750 sized venturi, they fall in line between the 750 and 850. That being said they are great carbs capable of making a lot of power. As mentioned when you talk to carb manufacturers and they start quoting cfm's ask what size the venturi's and the throttle bores on the base plate are.

The guys at BLP are great to deal with and very knowledgeable.
 
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