Speed Demon 650 or 750 for this setup?

allcarfan

The Answer Man

Founding Member

Apr 8, 2001

2,458

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56

North Atlanta

Dec 10, 2003

#1

• Dec 10, 2003

• #1

lightweight 331 stroker
Mildly ported twisted wedge heads (290/210cfm)
xe274hr cam:
* Advertised duration: 274 intake/282 exhaust
* Duration at .050 in.: 224 intake/232 exhaust
* Gross valve lift: .555 in. intake/.565 in. exhaust
* Lobe separation: 112 degrees
Ported and notched Performer RPM intake
1 3/4" headers

Engine will probably see 6700 rpms or so once in a while.

So...Speed demon 650 or 750?

I read an article where an engine made 400 at the flywheel and the 750 speed demon was too big.

Shane

 

G

gp001

Founding Member

Jun 30, 2001

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So. Cal.

Dec 10, 2003

#2

• Dec 10, 2003

• #2

650. My 347 makes about 400 fwhp and the 750 was too big for it as well.

Using 331 ci, 6700 max rpm, and 100% ve the formula says 709 cfm. Using 90% ve it comes out to 567 cfm. I don't think you'll ever see 100% ve, and you would still be over carbed.

 

allcarfan

The Answer Man

Founding Member

Apr 8, 2001

2,458

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56

North Atlanta

Dec 10, 2003

#3

• Dec 10, 2003

• #3

im probably going to be making closer to 475/500 hp at the flywheel. To my understanding the 650 flowed wet at 753cfm.

Thanks for your explanation GP. It doesnt get much better than that.

 

foghorn67

I'll save you the time and choke myself

Founding Member

Jan 10, 2002

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Orange County, CA

Dec 10, 2003

#4

• Dec 10, 2003

• #4

650. especially with them demons, they flow alot more then holleys.

 

brianj5600

Active Member

Sep 19, 2003

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Middle TN

Dec 10, 2003

#5

• Dec 10, 2003

• #5

A similar motor in MM/FF went over 100% ve. I would call tech at BG, they know there products better than any of us.

 

C

Clark

Founding Member

Aug 5, 1999

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Rowlett,Texas

Dec 12, 2003

#6

• Dec 12, 2003

• #6

Defintely 650, I have a 625 Road Demon on my 393W and it runs good.