Speed Demon 650 or 750 for this setup?

[allcarfan]

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

 

[gp001]

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]

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]

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

 

[brianj5600]

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.

 

[Clark]

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