Topic: Mike Rieck and Rick Stetson 35/28 K head mods.(ram air too)

[gschuld]

I wanted to thank Mike Rieck and Rick Stetson for the recent work on this head.  Mike especially deserves a lot of credit for putting up with me on this one.  He completely reworked a chamber damaged vintage Butch Pace ported early K head several years ago.  Jim French did the chamber weld repairs.  It was gorgeous when done.  It was kept old school, new guides, 33.5/28 SS valves, fresh double springs, new titanium retainers.

http://forums.sohc4.net/index.php?topic=158036.0

I had it on the shelf for a while and my mind started wondering about the possibility of intake valves bigger than 34 in a k head.

http://forums.sohc4.net/index.php/topic,175280.0.html

So, after some consultation(should have been with a shrink🙄), I asked Mike if he was willing to cut back into that lovely work and see if we (read Mike/Rick) could make 35/28 valves fit.

So we used Ferrea Superflow 6.5mm stem Mitsubishi EVO 8/9 35mm intake valves(credit Bear from Australia who used them in his 410 heads) which are just long enough to be able to cut the length down to size and recut keeper grooves.  Basically consider them valve blanks.

Both valves needed to be sunk farther for v/v clearance and a bit more since I wanted freedom to install a .430” lift cam.  Sinking valves farther creates ever increasing valve to chamber shrouding.
So each chamber was carefully milled with a 20 degree cut from the 71mm bore in.  This is to match the 20 degree dome at the perimeter on vintage 12.5:1 MTC/Venolia/Arias/RC Engineering etc pistons.

By cutting that taper, and matching it to the piston crown, it allows several things. 

1-a good amount of accurate squish area(aimed toward the spark plug)
2-a decent theoretical chamber shape.
3-far less valve shrouding than would otherwise be necessary

CycleX high lift cast iron valve guides and CycleX 6.5mm beehive spring and retainer conversion was used along with new CycleX K type keepers. New hardened stem caps were used too.  The recessed pockets on the head casting had to be clearance down to allow the tall (.430”) cam lobes to clear the space.  None of this is new news to some, the tapered chamber/domed piston concept has been used many times by racers in all the 2V headed sohc/dohc bikes in the 70s-80s.  But I thought some here would appreciate Mike and Ricks work.  Rob Muzzy would be proud.  Keep in mind this is only a useful concept if high compression is desired AND good squish area. Street compression pistons could work but will reduce squish area some(or completely depending on shape)

George

[gschuld]

Some more pics

[gschuld]

It may be hard to appreciate the amount of cutting and reshaping of the chambers when just looking at the finished chambers.  Here is a pic of one chamber after the 20 degree cut.  The finished chamber was blended in a bit so it’s not all that obvious.

But you get a sense of the squish band created with a 20 degree dome piston.

George

[bwaller]

So in a year or two how about shrinking to a 27mm in favor of a 36mm?  Just kidding! You know I'm all about this type squish. Good job, looks great guys.

[Old Scrambler]

Nice looking indeed

So now the K head with recessed valves and milled chamber somewhat resemble a 410 head. Somewhere on this site recent comments were made about having a sloped squish-band at a greater degree than that of the piston.

Nice to know I'm not the only one with Ferrea valves...........but flat-faces may have helped compression.

[Jerry Rxman Griffin aka MuthaF'er]

Very nice work

[dragracer]

That's a work of art. Now I know what to do with those Mitsubishi Evo valves I bought 5 years ago. Lol.

[gschuld]

That's a work of art. Now I know what to do with those Mitsubishi Evo valves I bought 5 years ago. Lol.

😎

George

[johno]

George ! your unstoppable !
Thanks for the pics they look great, you posted pics of the exhaust port cos its an easy photo, but I'm into inlets so if you get the urge to share feel free to snap away.
Also it would be good to compare the flow rates between your head and the head Mike done for me with the 34mm x 5mm versus your 35mm x 6.5mm. I have flowed mine at 10 inches and 28 inches to get a feel for the flow at different average gas speeds through the port ie 200 ft/sec and 300 ft/ sec. PM me if its secret squirrel stuff 🤪
Let me say George, when I built my race engine I had a lot of experience in porting, had my own flow bench / dyno,  an unlimited budget and searched the world for the best head to use regardless of who done it and what reputation they had. What I learnt was the people on this forum are blessed to have access to the skills of Mike. Mike is a special person and he gave me the most enjoyable business transaction I have ever experienced in a lifetime of auto and cycle racing. Enjoy your new toy George.
cheers Johno

[gschuld]

Nice looking indeed

So now the K head with recessed valves and milled chamber somewhat resemble a 410 head. Somewhere on this site recent comments were made about having a sloped squish-band at a greater degree than that of the piston.

Nice to know I'm not the only one with Ferrea valves...........but flat-faces may have helped compression.

Angled, or tapered or expanding whatever squish…. Well, since the pistons are constant crown, the 20 degrees are only for the first 1/4” in, then it gradually reduces angle from there. So effectively, there is a slight angled squish action going on. 

[gschuld]

Kind words Johno.

I am a proud repeat offender with Mike.  I totally concur with your thoughts.  Here is an intake/exhaust view while it was still old school (but with new) APE 33.5/28 6.5 stem valves.  I’m not 100% sure how much alteration was done to them since beyond blending in the bigger throat for the 35s.

Mike has the flow details and is welcome to share it, for science.  No secret squirrel concerns here.  Mike didn’t feel any desire to hide it either.  I wouldn’t have started the thread if that were the case.  It’s healthy to share info IMHO.

It wasn’t an extreme intake tract porting job with epoxy like yours was.  Originally, Mike kind of liked the porting for a 40yr old vintage job, so it was generally kept old school but he gave it whatever improvements he desired.  This head had a few lives.

It was drag raced in the 70s, #4 rod let loose long ago and hammered a ring depression into the chamber of the head from the piston edge. Then sat retired for a LONG time before I got it. 

I have a soft spot for true raced in the 70s stuff, and I get sadistic pleasure in conning Mike into taking pity on a battered old war horse when I know he FAR FAR prefers starting with a virgin head and going to town.  No artist likes to be asked to repair another artists old outdated work.  Thanks again Mike🙂

I recall the peak intake flow with the 35s at .400” was lower than your head produced FWIW(under 80cfm)

George

[Jerry Rxman Griffin aka MuthaF'er]

Mike is a human CNC 

[gschuld]

Take a really close look at those ports. The accuracy and consistency of the contours is amazing.

George

[PeWe]

Really beautiful head job! Technical deep throat porn!!

So, that head will continue to produce power long after 9000 rpm  when it usually fades off?

[gschuld]

PEWE,

I don’t have any reason to believe that this head is any sort of breakthrough regarding rpm potential compared to other ported heads.  I’m hopeful the large squish area will promote good torque figures, but I’m figuring the head will peak around 9000-9500 with the CX-10 or CX-12-84 cam and 11.5:1 or so compression at 997cc.  Maybe it will float near the hp peak a little past 10,000. That would be nice.

George.

[MRieck]

Thanks for all the kind words fellas.....you're making me blush. Flow numbers didn't improve that much over the 33.5 intake which indicates the port is limiting flow. The spigot entrance definitely holds flow back....it is to small. These engines really don't make power after 9,000 RPM .....the porting etc allows them to hang onto the power past that point.....the power doesn't fall on its face.

[MRieck]

Nice looking indeed

So now the K head with recessed valves and milled chamber somewhat resemble a 410 head. Somewhere on this site recent comments were made about having a sloped squish-band at a greater degree than that of the piston.

Nice to know I'm not the only one with Ferrea valves...........but flat-faces may have helped compression.

I agree but the valve starts getting heavy. Ti valves would have been the real deal.

[gschuld]

Yes, in fact the Ferrea 35s were necked down to 5.8mm under the valve head, and the combination of head shape and face dish allowed the 35s to be a few grams LESS than the APE 33.5s.  Combined with the beehive spring conversion, I was anticipating a tough setup.  This is, FWIW, on the factory intake seat.  35s are pushing it, but it seems there is reason to believe there is enough meat left in the seats for durability.

I wanted to experiment to see what could be done without going too crazy.

The next step up would be like Brent Waller said, 36/27 combo.  Same clearance as 35/28.  It required finding or having made 6.5mm 27mm exhaust valves (couldn’t find any and I prefer 6.5 stem) and new larger diameter intake seats for the 36s.

If I was starting with a blank head, I would have gone down that path.  But since I was working with a fresh rebuilt head with new 28 exhaust valves, 35/28 went in as the 28s remained.

Ferrea does make 36mm 6.5mm superflow intake blanks FWIW, I have a set.😉

Oh, FWIW, my personal desire to retain the OEM 6.5mm stem size is just that, a personal preference. I’m not against thinner stem valves at all.  Lots of benefits in the significantly lighter weight of those setups.

George

[bwaller]

What I learnt was the people on this forum are blessed to have access to the skills of Mike. Mike is a special person and he gave me the most enjoyable business transaction I have ever experienced in a lifetime of auto and cycle racing.


Right-on johno, I agree whole heartedly.

[Old Scrambler]

AND..................Mike is a decent fellow with which to have a face-to-face conversation........... and he poses serious questions

[turboguzzi]

that squish band approach is what i built into my Gpz750/810 too, following all what i read about Muzzy's phylosphy on the subject.
George, could be nice to see how those pistons looks. 

BTW, the picture you posted is of a two stroke with a very wide squish band, no way to build something like that in a four stroke... or at least, none i know off

[gschuld]

Yossef,

Sorry posting that drawing was sloppy.  I was just trying to convey the general idea as many seem to connect squish area only to matching the flat deck. 

The pistons are .333” tall dome, rounded crown. 20 degrees at perimeter.

George

[gschuld]

This should give a better visual of the squish area.  The paper is cut to match the cross section of the 12.5:1 piston.

1st pic is inline with the cam, the other two are about 45 degrees rotated in either direction.

I’d say it’s quite a nice fit.😉😎

George

[andy750]

AND..................Mike is a decent fellow with which to have a face-to-face conversation........... and he poses serious questions

++++1

Here is one from the archives...Mike sharing his knowledge on CR carbs

[gschuld]

Sorry for the crude pencil hand drawing, but everything in the marked area is effective squish. I find it hard to imagine a much larger percentage of bore area covered by squish than this.

George