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CVO Social => In The News => Topic started by: rayson56 on October 31, 2020, 03:15:41 PM

Title: Article on M8 CNC ported heads
Post by: rayson56 on October 31, 2020, 03:15:41 PM

Just stumbled across this write up from December of 2017 that I found very interesting and thought I would share.

https://thunderpress.net/editorial/columnists/motorhead-memo-head-stroking/2017/12/12.htm

Thoughts or comments?

Title: Re: Article on M8 CNC ported heads
Post by: OBB on October 31, 2020, 06:19:43 PM

Interesting read. Explains better what Harry was trying to explain to me at Maggie Valley this year. Thanks for the find.

Sent from my boring Droid phone.

Title: Re: Article on M8 CNC ported heads
Post by: FLSTFI Dave on November 01, 2020, 06:54:04 AM

Interesting article. 

Title: Re: Article on M8 CNC ported heads
Post by: HD Street Performance on November 01, 2020, 07:31:54 AM

Everyone gets an opinion. I knew this writer many years ago. Smart man for sure but we do not agree about the constraints and problem areas as it is pulled out of the mix of this engine assembly. With all of the heads regardless of brand, vintage, or engine the port package needs to be evaluated in the context of the rest of the motor assembly. Airflow demand and the dimensions / geometry to get where you want to be need to be evaluated on a case by case basis using math, dimensions / geometry, and established standards, despite standards being a bit defacto in the porting world. Velocity does matter but we should not lose sight in that pursuit that these are large motors with long strokes which on turn around / intake and beginning of exhaust (blowdown) have large airflow demand. Think in terms of the 150hp 130" M8, that is the equivalent of a 600hp 520" V8 in demand per cylinder. Open the barn door too big on either side however and they will be a turd and work better in excess of 6K rpm where we spend little time if any. But where really are the constraints? Just like SE twin cam ported CNC heads the M8 offerings are not that great, the SE extreme ported CNCs which were not out at the time of this article are slightly better. Eyes go to the intake with zero mention of the exhaust? What he mentions about intake velocity on the floor is not the low hanging fruit in this case, nor is the benefit of reduced valve stem diameter in the exposed port area. Marketing! When probing the ports it becomes evident where the hot spots are, not the roof so much and yes the short turn. Notice most of the cams and their timing for the M8. Tells a story about what it takes to get them to scale up even after we do our thing.
I welcome Kip to come to my shop and I can demonstrate some of what I am speaking about on the flow bench but we will be looking at both sides.