a little insite?   please - sbc porting

Have an interesting technique, tool or just anything related to porting? Post it here . . . please no bashing anyone for the model of engine they are working, we're here to share ideas . . .

Postby sheppard00 » Tue Jul 26, 2005 7:18 am

on the 302 head it gives me a peak rpm of 5200

and an air speed of 653fps
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Postby hollywood63 » Thu Jul 28, 2005 9:25 am

Sheppard,
I have a dumb question what does the symbol between the word bore and the number 2 stand for.
:p
Art
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Postby cspeier » Thu Jul 28, 2005 11:39 am

Shepard

If your saying that the port velocity of your port is 650 fps.. It will never work, ever! That's way to fast. It needs to be 1/2 that. In the old days that's what I thought. The faster the port the better. That thinking is totally wrong. I took a port that flowed 350 at 450 fps. Nice oval port round Dart/Buick head. We killed it to 340 at 290-310 fps and the car went an easy .10 faster and more RPM! I kind've bet any of the pros. like Curtis, would agree. Try it..
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Postby larrycavan » Thu Jul 28, 2005 6:05 pm

what does the symbol between the word bore and the number 2 stand for


It means to the power of the number. When it applies to 2 it's Squared..bore x bore.

The concept of a question being dumb should be eraticated from the face of the earth...

Larry
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Postby cboggs » Fri Jul 29, 2005 12:56 am

Chad is right, . ( hi Chad )

On a flowbench flowing at 28" h2o, .. I shoot for air speeds
around 280fps to a max of 350fps. Anything faster then 350fps
will choke under dynamic running conditions.

Now if the 650fps is based on the dynamic conditions of a running
engine, .. it's about the max.

anything past Mach .55 will choke, ..

Curtis
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Racing Flow Development.
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Postby sheppard00 » Fri Jul 29, 2005 7:07 am

(.00353 x RPM x stroke x bore^2)/min cross sectional area = Max Port

will someone use this formula on one of thier heads and see how it comes out... check it for me. I got it from someone else and don't have a probe to check air speed my self..

thanks

mark sheppard
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Postby cspeier » Fri Jul 29, 2005 8:45 am

Mark

Your math is correct, but the only way to know port speed is by a velocity probe. This is what I suggest. Look on this forum you can easily find everything you need to build you a manometer and pitot. You can find plans to build, which is peanuts in cost, a vertical manometer. I personally purchased a Performance Trends pitot tube and a 36" Dwyer manometer.

I'll promise you, you'll learn more about port flow and the dynamics of a port when you use it than ever grinding and flowing! Before probing, I've had SSR speeds of 400+ and couldn't figure out why the head either didn't flow or stoped flowing. The pitot is the ONLY way to find your high flow areas to know were you need to grind. If you need any help, email me and I'll send a photo of what I use. Your head will benefit from this.

Chad
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Postby sheppard00 » Sun Jul 31, 2005 8:57 pm

a pic would be nice... and a little explination on how to use it would also be helpfull.. thanks

mark
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Postby 114-1125072539 » Fri Aug 26, 2005 12:26 pm

cboggs wrote:Chad is right, . ( hi Chad )

On a flowbench flowing at 28" h2o, .. I shoot for air speeds
around 280fps to a max of 350fps. Anything faster then 350fps
will choke under dynamic running conditions.

Now if the 650fps is based on the dynamic conditions of a running
engine, .. it's about the max.

anything past Mach .55 will choke, ..

Curtis

Hello, I'm new here but have a question. I think i know the answer but am looking for a warm fuzzy. I'm looking at a turbocharged application and the inlet air temp is 270 F. Since mach number (for a perfect gas ) is a function of temperature only , I assume that these Mach index calculators use ambient conditions for Mach 1. Therefore , according to my Gas dynamics textbook Mach 1 @ 270 F is 17% faster than @ ambient. I think I can size my valves / cam and take advantage of this 17% increase in velocity thereby allowing slightly less valve / cam.

Do you agree or disagree ?

Thank you My Webpage :)
114-1125072539
 

Postby larrycavan » Sat Aug 27, 2005 11:10 pm

Hi Ron,

Welcome to Bruce's little corner of the world. 20 years ago I discussed the potential of a V8 ZX Kawaski motor with a friend of mine. I see you've turned that into reality. I like the way you think.

Larry
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Postby 114-1125072539 » Sun Aug 28, 2005 10:13 pm

It's a bizzare world, But a rules change will keep the V-8 out of competition. However, a new light has dawned. The largest displacement single engine Funnybike, with the most Boost is under construction. But since I can only have 16 valves instead of 32 ,I'll need to develop some better than normal ports to slay the competition.

Ron
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