M8 cylinder head puzzle

[sbcharlie]

things to consider in porting these heads. Since the throttle body is mount on the side in typical Harley fashion, the intake port track is curved. on intake valve will flow less. in most 4 valve applications the the spark plug is in the center of the combustion chamber. on these heads, the 2 spark plugs are located on the outside perimeter.beside air flow and port velocity a 4 valve head combustion chamber is measured as tumble type motion. the incoming air charge, as intake valve open the air tumbles across  the combustion chamber. 2 valve heads use swirl type motion. in my travel around the world these are some interesting things i have seen. most 4 cylinder head flow are based at 45inches of water on the super flow 600 benches, not the standard 28 inches seen on 2 valve heads. i have seen some head flow base numbers at 65 inches.i ask why and was told that this will give a very accurate view of flow and what is disturbing the air flow in a given port. so when you view these numbers review or look at base inch test number that being used. the other issue is the charge point in the port. this is the divider in the port that splits the air flow to each valve. you will find these charge point all over the place in different cylinder head designs. my game plan is 1. to cc both intake and exhaust port, this will assist you to determine port velocity. make a rubber mold of both ports, this will assist you figuring the CSA or cross sectional area of the port.2. flow the head in two different ways. flow with both valve opening together check to max lift of .500 at .050 increments. we do the same operation on straight designed port, example a v-rod. besides getting flow data this will assist you on the design of the charge point. sometimes you will weld to lengthen the devider  or you will shorten the charge point. on the M8 head you probably will grind more on the divider to capture air to enhance air flow. another way alter air flow is of course a larger valve. on some metric 4 valve heads we use 4 different size valve. this also adds a swirl affect to combustion chamber
i have also seen SIGN grooves cut in combustion chamber on intake side. they machine 2 grooves the outboard side of intake valve in combustion chamber, for detonation . going to be interesting to see different way guys will design these heads

[1FSTRK]

It can also be beneficial to use a different size intake valve in the short turn side and a totally different seat to chamber blend on the Harley type intake design.

Do you have data yet showing any benefits from switching from tumble to swirl ?

[sbcharlie]

i reread my post. we flow the head valves individually to verify air flow.  about 6 years ago i work with Bill Warner who was the factory  harley tuner. we work on Kawasaki 650 flat rack project, i install 4 different valves in the kawasaki  heads. Brian Smith was the rider and he started to win a lot of mile races. we also use this concept in the Honda crf 450 heads in moto cross. In 2013 my bike won the number 1 plate in AMA pro singles. the rules stated you can not change valve size. so i had web cam grind  a cam with different lift and duration on each lobe to get swirl.  i bet soon in the future  someone will design a eccentric style rocker arm for the M8 engine to alter one valve from the other. when i was in Australia working with Nissan they have domed valve buckets on there shim type rally cars. they were also working with different type valve buckets to alter valve timing events,  which would add swirl to combustion chamber. i think the future with the M8 is very exciting. there not to bad in stock form  sbc

[1FSTRK]

i reread my post. we flow the head valves individually to verify air flow.  about 6 years ago i work with Bill Warner who was the factory  harley tuner. we work on Kawasaki 650 flat rack project, i install 4 different valves in the kawasaki  heads. Brian Smith was the rider and he started to win a lot of mile races. we also use this concept in the Honda crf 450 heads in moto cross. In 2013 my bike won the number 1 plate in AMA pro singles. the rules stated you can not change valve size. so i had web cam grind  a cam with different lift and duration on each lobe to get swirl.  i bet soon in the future  someone will design a eccentric style rocker arm for the M8 engine to alter one valve from the other. when i was in Australia working with Nissan they have domed valve buckets on there shim type rally cars. they were also working with different type valve buckets to alter valve timing events,  which would add swirl to combustion chamber. i think the future with the M8 is very exciting. there not to bad in stock form  sbc

No rules out on the street so different size valves have not been a problem. I have seen regrinding of the rocker arm radius at the valve end to alter for ratio change from just off the seat to a different ratio at wide open as well as a ratio difference between the short runner valve and the long runner valve.

There will be a learning curve for the guys that use a form cutter in the chamber above the valve seat when they start doing four valve stuff but the smart guys catch on quick.
Looking forward to seeing what you do with these M-8 heads on your end, and if the work required will be justified in the resulting power gains.

Thanks for sharing here, keep us up to date.

[Durwood]

Charlie, have you measured chamber volume?

[sbcharlie]

have data to share. head volume 89 cc.   the valve to throat ratio intake 89% exhaust 80 % . interesting valve contact on intake is right on edge, exhaust 1.2mm from edge of valve. the intake valve seat profile  45 degree 1.2 mm wide below seat 65 degree 2mm 88 degree 9mm    the exhaust profile 45 degree 1.6  below seat 62 degree 4mm  87 degree 5mm . both seats there no top angle.   The charge point is very short in length and designed to direct air flow to spark plug.  my thoughts Harley really thought this head out. it going to be a real challenge to enhance air flow.  oversize valves thoughts 1-2 mm over on both on stock seats. intake manifold is plastic and well thought out. valves are the typical nail head design. sbc

[1FSTRK]

Nice detailed information, thanks for sharing it.
Do you have actual flow/velocity numbers yet? It will be interesting to see how the production pieces vary from one to another as well as from the advertised numbers.
Happy New Year

[twincam8888]

Interesting reading. Thanks for sharing.

[Breeze]

I've always been interested in , but am very low on really understanding flow dynamics. How,where,when doe variable valve timing change the porting data above? No need to get too detailed, you will loose me.

[No Cents]

 George Bryce of Star Racing is tearing down his own personal M8 bike over on the hdforum and he is posting detailed pictures of everything as he progresses.
George stated his stock M8 heads flowed way better than massaged on T/C heads do right out of the box. He said his 4 valve M8 heads flowed 300 cfm's at .500" lift bone stock. He was going to do some port work to them and he was going to post the results...but I haven't been back over there to see what progress he has made. He is bumping the bore size up and going to do some cam testing also.
For what ever reason...George is taking pictures of all this and posting them for all to see.

Ray

[DTTJGlide]

The flow #s are on pg 4 of his write up, pretty amazing #s right out of the box, they flow more @ .200 lift than stock TC heads flow @ .500 or above. Int 325 @ .500 315 @ .400 281 @ .300 Ex 235 @ .500 234 @ .400 225 @ .300, that should make some good #s once the cam makers get there job figured out. I think it's going to take someone with 4 valve experience to get it right, they're a whole new ballgame & need radically different specs to work right.

[N-gin]

Those are great numbers for sure, but what about higher lifts? And or bigger valves? I guess we will see. I still see a ceiling at 330, but this is on stock head and at least .200 less lift. Does anyone else think that there really isn't ground breaking unless there is 350 or more? The fact that they are getting 320 at.5 is amazing but it is still just 320.
Are the bigger cuin M8 heads the same? Maybe "bigger" heads in the future with screaming eagle?

[1FSTRK]

Anyone know
What diameter stems are in these heads?
What do the valves weigh?

[sfmichael]

great info - thanks everyone   

[DTTJGlide]

Valve stem is 6mm, the intake is 54.2 grams, exhaust is 54.4, retainer is 6.3, & keeper is .5 gram. This info & much more has been graciously shared in the article in HDF, very informative. Top names in the performance industry who are sharing some great information.

[sfmichael]

Valve stem is 6mm, the intake is 54.2 grams, exhaust is 54.4, retainer is 6.3, & keeper is .5 gram. This info & much more has been graciously shared in the article in HDF, very informative. Top names in the performance industry who are sharing some great information.

can you post a link...I don't look around much anywhere else and couldn't find it

[1FSTRK]

Valve stem is 6mm, the intake is 54.2 grams, exhaust is 54.4, retainer is 6.3, & keeper is .5 gram. This info & much more has been graciously shared in the article in HDF, very informative. Top names in the performance industry who are sharing some great information.

Thanks, I missed that post from Steve when i skimmed the thread.
Anyone have advertised and measure rocker ratio?

Appears that the even though the stock flow numbers look like a ported Twin cam head, the velocity numbers lack in comparison. Many may learn the value of velocity when they start trying to spin these engines fast enough to make power from all this easy to obtain flow. HP/CFM will be the number to check on these engines.

[Don D]

Good points Eric
I am optimistic about the new design but I just believe the treatment will be different to extract big power.
Plus there will be a new learning curve to really leverage this 4 valve pent roof design which is side fed. Camshafts that work the best will likely not be of similar timing to what worked with the EVO and Twin Cam. Reversion is an issue when overlap is added. So is high TDC lifts. Talking theory but 4 valve heads are not typically overlap friendly  below 4K rpm but excel at high rpms. This however is in the context of OHC engines which have the bore and stroke conducive to running well in excess of 6500 rpm. It's going to be interesting.

[N-gin]

Wood has a number of cams for this engine already that seem to be making 20+ with just a cam swap to a 222. The lower RPM in the cammed M8 stayed the same but 3k+ is when they start to shine. This was done by Fuelmoto. Great write-up by him.

[Don D]

Not really what I had in mind. I am speaking about bigger motors, bigger bore and trying to get a smooth reliable 150 out of one of these M8s
Lots more to come.

[mike jesse]

I have not done much research so bear with me here.

Do the 107 and 114 share the same head?

If not, what are the differences?

[1FSTRK]

Not really what I had in mind. I am speaking about bigger motors, bigger bore and trying to get a smooth reliable 150 out of one of these M8s
Lots more to come.

If you just make it big enough to use the volume of air at a low enough rpm it will be not problem.
117ci with a little work or 124ci with little to no effort .

[qtrracer]

George Bryce of Star Racing is tearing down his own personal M8 bike over on the hdforum and he is posting detailed pictures of everything as he progresses.
George stated his stock M8 heads flowed way better than massaged on T/C heads do right out of the box. He said his 4 valve M8 heads flowed 300 cfm's at .500" lift bone stock. He was going to do some port work to them and he was going to post the results...but I haven't been back over there to see what progress he has made. He is bumping the bore size up and going to do some cam testing also.
For what ever reason...George is taking pictures of all this and posting them for all to see.

Ray

350 @ .5" is the most recent numbers George posted that I saw.