[94cobra69ss396]

Does anyone know what the math formula is for figuring out the maximun horspower you can make with a particular valve size? I'm trying to figure out how much horsepower is possible with the 1.90/1.60 valves in my AFR 165's. I've done some research and it appears that the AFR 185 has the same exhaust flow as the 165 but a little more cfm on the intake. I'm assuming the increase is due to larger ports and intake valve at 185.

I want to know if I could get close to the same flow with porting but keeping the 1.90 valves or if I need to go to a 2.02 and then port the intake runners. I'm trying to work something out to buy Guy's 347 and I want to try and make mid to high 500 rwhp using my existing heads if I can buy it. I know I could make that if I moved to a set of 205's but that would be another $2000 that I don't have.

[enkeivette]

Any 500hp at the engine SB build that I've seen has at least 190s. 500 at the wheels? Jump up to the 200s with a solid roller no question.

I don't think a valve would really be the limiting factor, it's got to be the port behind it. A valve just covers a hole, and a 1.9" valve should flow as much cfm as a 1.9" pipe with an obstruction in front of it, minus the thickness of the valve stem. And obviously with a bigger valve there is more room back there to scoop out the port.

[enkeivette]

Have your 165s machined for 2.05s and 1.80s

[94cobra69ss396]

A 1.90 valve can only flow so much. I want to know what that is. Also, I'm already making 471rwhp with the 165's through the catted H-pipe. If I remove it I pick up 4 mph at the track so I assume I'm making about 500rwhp with it.

[enkeivette]

Holy crap. You know how to build an engine. Solid cam? 91?

[enkeivette]

I'll post on my engine forum and see if anyone has any answers for you.

[enkeivette]

http://speedtalk.com/forum/viewtopic.php?f=1&t=23941

[Vettezuki]

[94cobra69ss396]

Originally Posted by enkeivette

Holy crap. You know how to build an engine. Solid cam? 91?

Hydraulic roller with .498 lift and 220 at.050 with a 110 LSA. It made 436rwhp on 91 and 471rwhp on 100. I'll check out the link.

[enkeivette]

Boom! Could not have been a more perfect answer! There are like 4 calculators about valves on this page. http://www.wallaceracing.com/Calculators.htm

I think this is the one you were looking for specifically. http://www.wallaceracing.com/hp-valve-size.php