Carb CFM Calculator now up

This works real well(???)
I think my 48 IDA's are to small:


<HR> <TABLE style="WIDTH: 380px; HEIGHT: 200px; TEXT-ALIGN: left" cellSpacing=0 cellPadding=0 border=0><TBODY><TR><TH style="BACKGROUND-COLOR: rgb(255,153,0); TEXT-ALIGN: center" colSpan=3>Carburetor Size Calculator</TH></TR><TR><TD style="BACKGROUND-COLOR: rgb(255,255,153)">Engine Size</TD><TD style="BACKGROUND-COLOR: rgb(255,255,153); TEXT-ALIGN: left"><INPUT size=6 value=289 name=EngineSize></TD><TD style="BACKGROUND-COLOR: rgb(255,255,153); TEXT-ALIGN: center"><SELECT onchange=EngineUnitsChanged(this.form.EngineUnitsLb) size=1 name=EngineUnitsLb> <OPTION value=0 selected>Cubic Inches</OPTION> <OPTION value=1>Cubic Centimeter</OPTION></SELECT> </TD></TR><TR><TD style="BACKGROUND-COLOR: rgb(255,255,153)">Maximum RPM</TD><TD style="BACKGROUND-COLOR: rgb(255,255,153); TEXT-ALIGN: left"><INPUT size=6 value=7000 name=MaxRPM> </TD><TD style="BACKGROUND-COLOR: rgb(255,255,153); TEXT-ALIGN: center"></TD></TR><TR><TD style="BACKGROUND-COLOR: rgb(255,255,153)">Volumetric Efficiency (VE)
</TD><TD style="BACKGROUND-COLOR: rgb(255,255,153); TEXT-ALIGN: left"><INPUT size=6 value=90 name=VE></TD><TD style="BACKGROUND-COLOR: rgb(255,255,153)"></TD></TR><TR><TD style="BACKGROUND-COLOR: rgb(255,255,153)">Carburetor Type
</TD><TD style="BACKGROUND-COLOR: rgb(255,255,153); TEXT-ALIGN: left"><SELECT onchange=CarbTypeChanged(this.form.CarbTypeLb) size=1 name=CarbTypeLb> <OPTION value=0 selected>Stock</OPTION> <OPTION value=1>Modified</OPTION></SELECT> </TD><TD style="BACKGROUND-COLOR: rgb(255,255,153)"></TD></TR><TR><TH style="BACKGROUND-COLOR: rgb(255,153,0); TEXT-ALIGN: center" colSpan=3>Carburetor CFM</TH></TR><TR><TD style="BACKGROUND-COLOR: rgb(51,255,51)">Carburetor Size CFM</TD><TD style="BACKGROUND-COLOR: rgb(51,255,51); TEXT-ALIGN: center"><INPUT readOnly size=6 value=52682 name=CarbCFM> </TD><TD style="BACKGROUND-COLOR: rgb(51,255,51)"></TD></TR><TR><TD style="BACKGROUND-COLOR: rgb(255,204,153); TEXT-ALIGN: center" colSpan=3><INPUT onclick=CalcCarbCFM(this.form) type=button value=Calculate name=CFMCalc> <INPUT onclick=ResetCarbCFM(this.form) type=button value=Reset name=ResetCFMCalc> <INPUT onclick=SampleCarbCFM(this.form) type=button value=Sample name=SampleCFMCalc> </TD></TR></TBODY></TABLE>
 

Sandy

Gulf GT40
Lifetime Supporter
I guess I had better add a bit more error (fool proofing) checking on user input...

Try 0.90 instead of "90" you had entered for the VE that should yield better results. These number may not work well with IR (weber) CFM ratings.

I'm going to need to see your dyno sheet too -

From the CarbCalc page
  • Stock Engines VE = 0.75 - 0.85
  • Mild Built VE = 0.85 - 0.90
  • Racing Engines VE = 0.90 - 1.0
  • Anything more then that needs a dyno sheet to prove it!
Sandy
 
Last edited:
For your VE use the decimal point, ie 90% = .9, 100% = 1.00 .

Doesnt really work for webers as you have to use one cyl vol. eg ; approx 36 cu in for 289.
 

Sandy

Gulf GT40
Lifetime Supporter
CarbCalc page updated to issue a helpful message if VE out of whack, and a disclaimer about Weber Carbs ;-)

Injector calc almost done, initial view (no charting) is here -

Hit the "Sample" button to get an idea how to work the values. I'll be adding help and charting for these as time permits.

Injector Size Calculator

Sandy
 

JimmyMac

Lifetime Supporter
Guys,
Do these formulae work with a Ford / Autolite in-line carb & Cross Boss manifold set-up ?
I would appreciate any help.
 
Last edited:
James,
If your throttle bores are 1-11/16 then its 850cfm ( Trans Am), if its 2-1/4' its 1400cfm ( Nascar ). Assume you dont require the p/n's:)

That little 289 is going to be a hummer to use that airflow!!!
 

JimmyMac

Lifetime Supporter
Jac,
I bought one recently with a pile of spares and three sets of manuals but the paperwork could be for a moon lander vehicle for all I know. I need to learn about these things.

I was told that these carbs beat the Webers hands down for progression.
 

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Sandy

Gulf GT40
Lifetime Supporter
I would imagine if they have a plenum under them they might be close. If IR under the hood then maybe not so much, but would be something of a start. These calcs are really estimates for more conventional setups but always a good starting point as it is easy to visualize a Holley like carb ;-)

I have seen a few of the autolite setups and they are as cool looking as webers, maybe more so since they are from Autolite and hens tooth rare I'm guessing.

Sandy
 

JimmyMac

Lifetime Supporter
I would imagine if they have a plenum under them they might be close.
Sandy
That's exactly what I was thinking Sandy.
I also agree that it's a pretty cool lump of kit and I would like to give it a go some day. I have an ambition to do a nice Mustang some time so I decided to buy this as a reminder.
Many thanks for posting the calculator.
 
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