I've been feeling the short turn radius of the exhaust ports on the PR3 heads i have here with my finger. "looking at it is impossible to tell" at least for the untrained eye. I notice that Cylinder 2 and 3 has steeper short turn radius compaired to Cylinder 1 and 4. That must be due to the factory casting.

Question, for full ported heads are these radiuses taken out so they are symmetrical?

 

Yes. Cylinder 2 and 3 exhaust ports have higher short turns.

"Full Ported" head is loosely used term by many.

 

Thanks for the confirmation. What is the reason behind the higher radiuses? Surely they will cause flow variations between ports.

Its not that difficult to actually feel the quality of a port by feeling it with the fingers. If difference between ports can be felt, i can't imagine how much difference it will register on the bench.

I wonder if the 'cnc' ported heads have been ported to flow within 1% or 1 to 2cfm varation between ports.

 

Well a good porter is just a glorified "finger ******" LOL. That's why Don Tyrell founder of speedtalk.com sells the secret of usint a 3/4" piece of sand paper. Guess what you do with it? The answer is in the first sentence here.

There are some advanced techniques used by Cosworth in their multi-valve heads. I've been studying some of this. But I am just a lackey so I haven't gotten far.

 

Only if the original CNC program has a diff. of 1-2%. Programs are usually digitized from an existing "hand ported" head.

 

I wonder if these hand ported heads have been ported to flow within 1% of each cylinder before its put on the cnc program.

I'm sure if we flow some of the 'ported' heads in the market, the flow variation between cylinders are all over the place.

I want to find out who flows every cylinder and matches the flow before they sell their 'fully' ported head.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Don Lackey &raquo;</TD></TR><TR><TD CLASS="quote">Well a good porter is just a glorified "finger ******" LOL. That's why Don Tyrell founder of speedtalk.com sells the secret of usint a 3/4" piece of sand paper. Guess what you do with it? The answer is in the first sentence here.

There are some advanced techniques used by Cosworth in their multi-valve heads. I've been studying some of this. But I am just a lackey so I haven't gotten far.

</TD></TR></TABLE>

Its not rocket science is it?

 

It is and it isn't.

Most of the time the ports, especially the intake ports will flow about the same because the intake ports are the same dimensions. You would have to purposely try to make them different.

You can have a 1% variance in flow from just reading the scale on the flow bench differently so I wouldn't chase that last 0.5% of consistency.

 

On EX ports of the Bseries heads #1 & #4 have larger turns toward the center of the heads and flow worse than #2 and #3 what you are seeing is the attempt to balance them out.

 

Everything is a compromise.