Porting stock M8 heads v. SE CNC

[Eccool]

Picked up the January east edition of Thunder Press at the local dealer today.  There is an article in there by Kip Woodring basically stating that ported stock M8 heads cannot meet the performance level of the SE heads because the stock ports are too big.  He states that if the ported stockers even came close to the SE heads, that it would involve so much work, that the cost of the ported stockers would exceed that of the SE heads.  I know we have a lot of head porters on here, I was just wondering what you guys think.  Thank you very much!  Merry Christmas all!

[1FSTRK]

HD has learned from the Indy engine builders over the years. They were not going to supply the after market with stock cores form porting. They did the same with the throttle bodies, and 883 cylinders. Easy enough to design parts that cannot be upgraded.

[Eccool]

HD has learned from the Indy engine builders over the years. They were not going to supply the after market with stock cores form porting. They did the same with the throttle bodies, and 883 cylinders. Easy enough to design parts that cannot be upgraded.

So are you saying you agree with the article?

[1FSTRK]

Absolutely.
I have been posting that here for a year now. If you look at all the threads and guys that started out porting M-8 heads for a 107 they never posted dyno info until they put big bore kits on and then the HP/CI numbers are still running in the Twin cam range even though the heads flow tons more CFM. They are take ports that are to big and making them bigger just to say they improved the flow. Then they all try to grow the motor big enough to start to use those big ports.

[K4FXD]

Put a 3&5/8ths stroke crank in one and spin the crap out of it. 

[sbcharlie]

its interesting read his article, i see the valve guides were replaced in pictures .  i have port many stock casting with great results. you need both air flow and port velocity. you can achieve both in a stock heads. the CNC ported head work well if you want to drop $500.00 more into them to make them work. bunch of snake oil . sbc

[prodrag1320]

have to agree with SBC.done several sets of stock heads with very good results

[Don D]

The stock heads may be just right as far as cross sectional area and just need a little help with swirl. Lemons to lemonade when combined with a camshaft that is tailored to the characteristics of the pent roof head and the relatively large CSA and valve area.
I have a set I will mess with this summer. They will be getting a very different valve job then the twin cams.

[1FSTRK]

Porting them for flow bench shootouts is no problem, getting them to make and exceed the HP/CFM that we see in hi performance Twin cam set ups is something else entirely.

These 4 valve heads are supposed to be a big improvement over the two valve heads, they flow 50% more air right front the factory.

[rigidthumper]

IMO the intake to exhaust ratio could be better. 

[badcooky]

More cubes might get some port velocity .

[sbcharlie]

lets get back to basics here. here the way i approach a cylinder head. you baseline it. things to consider the valve to throat ratio. flow test to get base numbers . the most important test probe the port for port velocity. get rubber mold of port, this will give you CSA numbers. one ,these stock heads flow well and guess what they have 350 port velocity. when you port a head, most important piece of puzzle is the valve job. these head do not need much except in valve profiles and adding width to short side radius. yes we see enhanced airflow and the port velocity gains or is equal. yes the CNC se heads have smaller intake ports, but velocity is about the same. i have seen Harley do some nice work on there CNC ported heads and there other offering. The M-8 heads need a lot of work. i have redid 2 set, and customers are happy.  the one thing i have seen using 4 different valve diameters  wake these heads up.  another interesting thing on these heads using stock valves sizes are not a bad way to go.  if you heart desires the cnc heads from harley buy and enjoy sbc

[Nastytls]

Is one a better foundation for performance, or can similar results be had by both?

[sbcharlie]

i am going to make a u-tube this week and document the port velocity in a stock head, a CNC head, and a ported head to show you that there BS about port velocity. sbc

[1FSTRK]

lets get back to basics here. here the way i approach a cylinder head. you baseline it. things to consider the valve to throat ratio. flow test to get base numbers . the most important test probe the port for port velocity. get rubber mold of port, this will give you CSA numbers. one ,these stock heads flow well and guess what they have 350 port velocity. when you port a head, most important piece of puzzle is the valve job. these head do not need much except in valve profiles and adding width to short side radius. yes we see enhanced airflow and the port velocity gains or is equal. yes the CNC se heads have smaller intake ports, but velocity is about the same. i have seen Harley do some nice work on there CNC ported heads and there other offering. The M-8 heads need a lot of work. i have redid 2 set, and customers are happy.  the one thing i have seen using 4 different valve diameters  wake these heads up.  another interesting thing on these heads using stock valves sizes are not a bad way to go.  if you heart desires the cnc heads from harley buy and enjoy sbc

So where is the power?
Why does all this hype not translate to better HP and TQ/CI?

[sbcharlie]

why don't you ride one and find out.  were the twin cams great when they first came out, took some time. these M-8 are head and shoulders better than a twin cam.  and there going to keep getting a lot better

[1FSTRK]

why don't you ride one and find out.  were the twin cams great when they first came out, took some time. these M-8 are head and shoulders better than a twin cam.  and there going to keep getting a lot better

I have, they run fine but this is a Tech site and we are talking about real  Tech not just can we make a living selling new motorcycles because they are different and porting heads for a living because they flow more air regardless of any real advances in power over the other heads we made a living porting.

[sbcharlie]

you are correct it is a tech site. what wrong with giving correct technical information out so the tech type people can make think it out . again its a tech site not a platform to what ever

[1FSTRK]

you are correct it is a tech site. what wrong with giving correct technical information out so the tech type people can make think it out . again its a tech site not a platform to what ever

Simple math is I have two twin cam bikes, a 05 95" A motor makes 1.26 HP/CI and a 07 110" B motor makes 1.2 HP/CI. Both a engines are about ten years old and have been trouble free. Both are built stock Twin cam head that are ported. So where are the M-8 builds that make 1.2 HP/CI by porting the heads and adding a TB to a good stage two set up?
The testing  that has been posted for stage one and stage two M-8's runs parallel to the twin cam counter parts for HP/CI and we all know the the stock M-8 heads out flow the stock twin cam heads. So now we are marketing ported heads and where are the 1.2 HP/CI set ups?

More important where are the gains from the 4 valve heads

[badcooky]

 4V heads like revs HD's don't rev much so the theoretical gains aren't there.
With a little work the M8's are stomping Twin cams that are highly modified though.
Dyno HP is just that a static number, real world the M8's kick ass.

[1FSTRK]

4V heads like revs HD's don't rev much so the theoretical gains aren't there.
With a little work the M8's are stomping Twin cams that are highly modified though.
Dyno HP is just that a static number, real world the M8's kick ass.

Really, well maybe, but only on the internet.

Added
Actually you will find the testing with the M-8 is showing just the opposite of your claims. The short comings in HP/CI are  being explained away will graphs showing power coming in earlier there by giving more area under the curve compared to many Twin cam conbos

[BVHOG]

We have a member here doing testing and sharing the info no charge, whatever the motivation may be. Please don't piss him off, the rest of us would like to hear what he has to say.

[harleytuner]

4V heads like revs HD's don't rev much so the theoretical gains aren't there.
With a little work the M8's are stomping Twin cams that are highly modified though.
Dyno HP is just that a static number, real world the M8's kick ass.

Ever compared the gearing  between the 6 speed TC and the M8?

[krwson]

4V heads like revs HD's don't rev much so the theoretical gains aren't there.
With a little work the M8's are stomping Twin cams that are highly modified though.
Dyno HP is just that a static number, real world the M8's kick ass.

Ever compared the gearing  between the 6 speed TC and the M8?

Surely no expert, but my resurch indicates primary drive and ratios (overall) are the same TC & M8's   

[harleytuner]

4V heads like revs HD's don't rev much so the theoretical gains aren't there.
With a little work the M8's are stomping Twin cams that are highly modified though.
Dyno HP is just that a static number, real world the M8's kick ass.

Ever compared the gearing  between the 6 speed TC and the M8?

Surely no expert, but my resurch indicates primary drive and ratios (overall) are the same TC & M8's   

I started looking into it briefly awhile back and never finished researching the ratios.  On the dyno the gear graphs ate quit different for same grear runs between the 2.