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Discussion Starter · #1 ·
Any ideas on what size carb to put on my combo?

Here is my combo

408w, 11.7 to 1 comp. 4340 crank, h-beam rods, srp pistons
comp cam solid lift 240 , 250 @050, 586,593 lift
victor jr intake
1 3/4 inch super comp hookers,3 inch collectors
World product sr heads with some work
Car is 2950 with me in it
71 maverick 9 inch rear all strange
4.57 gears
pa super comp c-4
pa 9 inch 4500 stall
32x14x15 mt slicks

Also how much rwhp and fwhp do you think at what rpm?
I called pro-systems and they have to have an idea how much hp it has and how high im going to spin it ,so any info would help. I dont know yet where it will make most power at 6200 ,6400, 6600 any ideas? Or i could buy an off the shelf one if i knew about what size, 850hp,950hp? Hoping to run 10.50s or better.

thanks
 

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You'll want Patrick to set one up for you....

I'd say 550-600 FWHP if the heads flow a good number....you should probably be able to give him a ballpark on the shifting. Say 64-6600 or so.

I estimated several areas of the spec sheet I filled out for him. Haven't run the carb yet though.
 

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Discussion Starter · #3 ·
I have a 750hp. Do i send him that one or get a new one from him?
 

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Check and see if he thinks the 750HP can get the job done with his setup/tune.

Mine has a custom base plate and a 780 main body.
 

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Discussion Starter · #5 ·
Ok thanks for your help. Once i get it all together ill post my times.
 

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Discussion Starter · #7 ·
Looks great with the billet base plate. Also thinking of buying some victor jr heads before i assemble the engine. Would buy afr heads but money is tight after building my motor.
 

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Looking back on my guess on hp.....I'm probably high with the heads you have now. The Vic Jr would be a good choice and they have room for improvement down the road (porting).

MM&FF got 520hp out of the Vic Jr when they tested them in their big cylinder head series.
 

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Discussion Starter · #9 ·
Thanks, so you think the victor jr's will give me 550 rwhp?

<font size=-1>[ This Message was edited by: DragRacr on 3/25/06 11:06pm ]</font>
 

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Discussion Starter · #10 ·
Really , like i said trying to get it to run low 10's. Don't know what kind of hp that will take.

<font size=-1>[ This Message was edited by: DragRacr on 3/25/06 11:08pm ]</font>
 

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You'll have a tough time making that to the wheels n/a without some semi-radical parts.....heads & cam.

A rule of thumb is 2 hp per cfm. That's FWHP.

So, you'd need a head flowing 300+ cfm and a bunch of matched parts to put 600 at the flywheel.

The MM&FF 520hp was an engine dyno.

You can look at this calculator and get an idea of where you need to be power wise:

http://www.fordmuscle.com/calculators/horsepower.shtml

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<font color="red">***New Project***</font>'89 LX 408, SCAT crank & H-beams, Probe pistons, AFR 205, Rawls SFT cam, Vic Jr intake, Pro Systems carb, UPR K & arms w/coil overs.....more to come!!!

<font size=-1>[ This Message was edited by: mstngjoe on 3/26/06 1:10am ]</font>
 

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A rule of thumb is 2 hp per cfm. That's FWHP.
2 cfm per HP maybe. Thats still a bit heavy though. 1 1/2 cfm per HP seems more realistic for what your'e running. All depends on cam, compression and flow in and out. Carbs can do amazing things even when undersized. Look at Nascar.

Anyway for that combo I'd run a 950 HP or equivalent although you could probably do just fine with a 850. I know Ive gone a bit over 600 HP on the dyno with a 10:1 compression 482 inch engine before . I'm running a 950 on my 438 from pro-systems and couldnt be happier with it.
 

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On 2006-03-27 12:51, chipmechanic wrote:
A rule of thumb is 2 hp per cfm. That's FWHP.
2 cfm per HP maybe. Thats still a bit heavy though. 1 1/2 cfm per HP seems more realistic for what your'e running....
You may be correct for what he is running.....

The reason I put "rule of thumb" was to avoid any absolutes on a given combination.

If you were to optimize the rest of the combination for peak performance, the "2 hp per cfm" may even be on the low side.

Superflow has used a formula for predicting power output based on flow for some years. And although it includes the whole intake system....carb, manifold, head....it's still valid for using just peak head flow numbers if you adjust it down a little from the number Superflow references....which is 2.7 at 25" H2o.

Which is not to say that a head could not produce more power.


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<font color="red">***New Project***</font>'89 LX 408, SCAT crank & H-beams, Probe pistons, AFR 205, Rawls SFT cam, Vic Jr intake, Pro Systems carb, UPR K & arms w/coil overs.....more to come!!!

<font size=-1>[ This Message was edited by: mstngjoe on 3/28/06 4:27am ]</font>
 

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OK I see what the confusion is about here. His question was about carburetor cfm . Your reply was concerning intake port flow assuming a balanced exhaust.

The 1 1/2 cfm per HP I was referring to was carburetor flow to HP assuming a 90 % Volumetric Efficiency.
 

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Discussion Starter · #15 ·
Thanks guys. I bought a set of victor jr heads, will be here tuesday.As far as the size carb or what kind is still up in the air.I've talked to barry grant,holley and pro- systems,and haven't decided which one or what size yet.Bg says mighty demon 750, he said it really flows 930 cfm.Holley say 750hp which i have and they both said i could go bigger because of my stall but the 750 will out accelerate the bigger carb off the line, but that makes me wonder about the big end.As far as my combo putting me in the low 10s i think it will.THere are to many people i race with that has close to the same combo as i have that runs 10.20s.I just dont want to over carb.I want not only to be fast but also consistant.As a bracket racer i want that instead of all out heads up type carb.
 

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Discussion Starter · #18 ·
Thanks for all your help on my posts.If i can ever help you out you let me know.
 
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