Valve lift - advice needed please

[trickymex]

First of all i would like to say Hi to all

Now for my questions

I am building a ford crossflow and i am just trying to work out what the valve lift + duration means and how it affects the performance of the engine i am building

The engine i am using at the moment is a 1760cc with a kent 244 cam

This cam is 290 deg with 11.3 valve lift on the inlet and the exhaust

I have read and heard from a few people that you should not go much over 25% of the valve diameter with the valve lift as it does not improve flow very much and it puts undue stress on thevalve gear

Well my valves are inlet 41.3 and exhaust 34.9

So 25% of the inlet is 10.325 and the exhaust is 8.725

I am running 11.3 on both

My questons are is this true about the valve lift??

And is the extra valve lift there for any other reason??

It just seems odd to me that they have put all this extra lift there for no reason.

Ricky

[Guy Croft]

Ricky, hi

It depends on the flow characteristic of the port, the flow will peak at some valve lift, that is usually the lift target. As a general guide for maximum power you should try & lift the inlet as high as possible within the allowable safe lift stated for the springs. Have a read of some of the features at:

http://guy-croft.com/viewforum.php?f=2

GC

[trickymex]

Thanks for the the response

So should i put the head on a flow bench and see what valve lift the head flows best at and get a cam to that lift and no more??

Where can i get a flowbench from and how much should i expect to pay for it??

Thanks

Rick

[Guy Croft]

Rick, hi

most folks - like me - use Superflow rigs of varying size, I'm not referring to costs here, but they do have a website and you can ring their European office and ask them.

I can test your head of course, no need to buy a rig just for that. E mail me if you want me to check it out.

GC

[trickymex]

Thanks Guy,

I may take you up on your offer, but the main reason that i was thinking of getting a flow bench was i would like to do a few heads my self.

Thanks for your advice

Ricky