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Old 03-11-11, 08:40AM   #16
Zedo
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Quote:
Originally Posted by Aaron View Post
EC is right. Port volume really doesn't matter, it's the minimum cross sectional area of the intake port matched to the engine displacement and max engine speed.


that's all relative. Port volume requirement is directly tied to engine size and rpm range. A 500-550 CID engine (i.e aftermarket Pontiac IA or MR-1) isn't going to have a small volume port. Look around at what the fastest cars are running for port volume now.

in the old days a fully ported Pontiac iron head had maybe 190-225 cc's

now everyone is banging on 300 cc's or larger

small block Chevys, circle track/drag racing, have 290 cc intake port, splayed valve heads, for only 350-400 CID

http://www.m2race.com/product_specs.asp?ID=50

GM Splayed Valve
- Product Specifications -
Head Name: Splayed Valve
Engine Type: SB Chevy 358" - 400"
Manufacturer: GM
Applications: Drag Racing, Oval Track

FlowTest Data
Bore Diameter: 0
Intake Valve Diameter: 2.23
Exhaust Valve Diameter: 1.55
Chamber Volume: 45cc
Intake Port Volume: 288cc



if they are using 288 cc heads for a small block 350 CID Chevy, think what a 500 CID Pontiac needs

certainly not the same exact port volume, for an extra 150 CID, unless the engine is being revved a lot lower
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Old 03-11-11, 05:45PM   #17
Aaron
 
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Port volume is determined by length and area of the port. Areas determine velocity on the running engine which is what matters, not volume. The larger the engine and higher the rpm, the more area needed (which intern drives larger volumes). I'm pretty familiar with what stock and aftermarket heads have to offer in area.

A 500 CID engine at 7000 rpm will need a minimum area of ~3.15 sq in for good power. That's a 2.25" valve with a 45 deg and the minimum area in the throat.


Quote:
Originally Posted by Zedo View Post
that's all relative. Port volume requirement is directly tied to engine size and rpm range. A 500-550 CID engine (i.e aftermarket Pontiac IA or MR-1) isn't going to have a small volume port. Look around at what the fastest cars are running for port volume now.

in the old days a fully ported Pontiac iron head had maybe 190-225 cc's

now everyone is banging on 300 cc's or larger

small block Chevys, circle track/drag racing, have 290 cc intake port, splayed valve heads, for only 350-400 CID

http://www.m2race.com/product_specs.asp?ID=50

GM Splayed Valve
- Product Specifications -
Head Name: Splayed Valve
Engine Type: SB Chevy 358" - 400"
Manufacturer: GM
Applications: Drag Racing, Oval Track

FlowTest Data
Bore Diameter: 0
Intake Valve Diameter: 2.23
Exhaust Valve Diameter: 1.55
Chamber Volume: 45cc
Intake Port Volume: 288cc



if they are using 288 cc heads for a small block 350 CID Chevy, think what a 500 CID Pontiac needs

certainly not the same exact port volume, for an extra 150 CID, unless the engine is being revved a lot lower
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