Big 32/28mm Valve Head

delray

Well-Known Member
#22
I believe one of the down falls of the honda 14cc head doesn't flow as good as your head you have on.
You could just mill more off your head...total of .080 and that should give a 12+ compression.
I would look and see if you can find a 93 octane eth...free gas and stay away from the racing gas.
Or just keep running with what you got..11+ compression and run 91 octane eth..free
If you do mill more off you might have to check push rod length.
 
#23
I don’t really want to mill much if any off a head as the big benefit of these straight valve heads are the increased piston to valve clearance and ability to run higher lift cams without interference. I believe a 14cc head with the right seats installed for some bigger 27/25 valves or even the 28.5/25 ole4 has done would be the ticket
 
#24
FWIW lift is one of the least important causes of v to p clearance. Duration and lsa are what you need to understand. As far as stock heads are concerned the worst flowing stockheads I have seen are the 18cc symmetrical chamber heads. However there are many different castings of the same head and they all vary somewhat. They can all be ported to flow well.
 
#25
FWIW lift is one of the least important causes of v to p clearance. Duration and lsa are what you need to understand. As far as stock heads are concerned the worst flowing stockheads I have seen are the 18cc symmetrical chamber heads. However there are many different castings of the same head and they all vary somewhat. They can all be ported to flow well.
I think what I am looking for is a 14cc head with 27/25 valves. With my mild cam and a 24mm flatslide I believe that would be a good setup for what I need
 

delray

Well-Known Member
#26
my understanding was not so much flow of the port. more with installing a larger valve in the small chamber being more restricted having the valve very close to the side of the chamber. not allowing much air flow unless it's has a radius cut around it. maybe not so much of a problem with the 27 valve. if ole says it good then I would go with it. second question I have and I can't answer this and maybe ole can. on the newer 212's come factory with the larger valves they couple of the dowel pins holes in the block/head are different size/location or not then a early clone and Honda's(14cc head)?
if indeed you can do all the mod's at once . think you will see a difference performance. good thing is you already have the power,so little extra won't hurt a bit.
 
#27
my understanding was not so much flow of the port. more with installing a larger valve in the small chamber being more restricted having the valve very close to the side of the chamber. not allowing much air flow unless it's has a radius cut around it. maybe not so much of a problem with the 27 valve. if ole says it good then I would go with it. second question I have and I can't answer this and maybe ole can. on the newer 212's come factory with the larger valves they couple of the dowel pins holes in the block/head are different size/location or not then a early clone and Honda's(14cc head)?
if indeed you can do all the mod's at once . think you will see a difference performance. good thing is you already have the power,so little extra won't hurt a bit.
The chamber does require unshrouding just the same as a 18cc head or a 22cc head. The area that is shrouded is similar on all of them because of the bore, no sense enlarging it further or you have no headgasket support. I use a ball end mill on a rotary table to unshroud as in the first picture. Also all heads I flow test are on a 70mm bore adapter. My bench has sliding sleeves so I can fit the correct bore adapter to match the engine bore. I am building a 72mm tillotson motor and that allows me an additional .040 for widening the chamber. You do need to open up the dowel holes on the clone heads for use on the non hemi predator. For this build buying a ported head and a mikuni flatslide I think is poor bang for the buck (185 + 95) The best bet is keep the chikuni get the seat and throat cut correctly for a 28 or 28.5 intake and call it a day. Also the 14cc heads I do are close to 16cc if they are not milled. One last thing is if you go get a larger intake you can mount the head valve seats up and use strips of emery cloth about 5/16ths to 3/8 wide thru the port an out the valve hole and go in a shoeshine motion to put a radius on the short side brings up low to midlift flow a lot. Also the MCSA of these heads is the interface of the runner to the bowl. Leave runner opening alone but you can widen it just a bit at the last 3/8ths of an inch before the valve bowl and the entry to the bowl. Then you can raise the root and streamline around the guide a bit. Do not get carried away. The runner taper is good for hi lift velocity but when you open it up a little just before the bowl it slows down the air a bit and makes it a bit easier to navigate around the short side.
 

Attachments

delray

Well-Known Member
#28
The chamber does require unshrouding just the same as a 18cc head or a 22cc head. The area that is shrouded is similar on all of them because of the bore, no sense enlarging it further or you have no headgasket support. I use a ball end mill on a rotary table to unshroud as in the first picture. Also all heads I flow test are on a 70mm bore adapter. My bench has sliding sleeves so I can fit the correct bore adapter to match the engine bore. I am building a 72mm tillotson motor and that allows me an additional .040 for widening the chamber. You do need to open up the dowel holes on the clone heads for use on the non hemi predator. For this build buying a ported head and a mikuni flatslide I think is poor bang for the buck (185 + 95) The best bet is keep the chikuni get the seat and throat cut correctly for a 28 or 28.5 intake and call it a day. Also the 14cc heads I do are close to 16cc if they are not milled. One last thing is if you go get a larger intake you can mount the head valve seats up and use strips of emery cloth about 5/16ths to 3/8 wide thru the port an out the valve hole and go in a shoeshine motion to put a radius on the short side brings up low to midlift flow a lot. Also the MCSA of these heads is the interface of the runner to the bowl. Leave runner opening alone but you can widen it just a bit at the last 3/8ths of an inch before the valve bowl and the entry to the bowl. Then you can raise the root and streamline around the guide a bit. Do not get carried away. The runner taper is good for hi lift velocity but when you open it up a little just before the bowl it slows down the air a bit and makes it a bit easier to navigate around the short side.
the old 212's or I should say the ones that first came with the small valves had the small dowel pin locations has the clones and honda's . then they had to change the design? early 212's are gen1"s and newers are gen3's?
even with the radius cut in the head that's still not bad for a stock unmilled head that's going on a 2.835 bore. still put you in the 12.1 comp.
for bryan he wouldn't have to mill much to keep is compression up on a 212 bore. i am assuming ole you are running narrow stem ss valves.
when i was cutting a radius my tecumseh 356 build i use the boring bar setup and fab a tool holding with a piece of high speed tooling with a radius cut into it. it work good. now that i got a rotary table i will try it with a ball end mill.
explain little more on the flatside carb issue. are you saying he should stay with a 22mm round or can he still improve with maybe a 24mm round?
 
#32
It's here somewhere. I did a more exhaustive test last year trying to understand why when flowing the head w/carb and manifold I would lose some CFM. I put it all in a excell spread sheet.
 

delray

Well-Known Member
#34
so at the end of the day if bryan was to use a 14cc honda head with 27/25 valves or the head he as on now with 27/25 valves and the head just milled correct compression. let say 12:1 he really won't achieve anything by building a 14cc honda head.
 

delray

Well-Known Member
#36
The chamber does require unshrouding just the same as a 18cc head or a 22cc head. The area that is shrouded is similar on all of them because of the bore, no sense enlarging it further or you have no headgasket support. I use a ball end mill on a rotary table to unshroud as in the first picture. Also all heads I flow test are on a 70mm bore adapter. My bench has sliding sleeves so I can fit the correct bore adapter to match the engine bore. I am building a 72mm tillotson motor and that allows me an additional .040 for widening the chamber. You do need to open up the dowel holes on the clone heads for use on the non hemi predator. For this build buying a ported head and a mikuni flatslide I think is poor bang for the buck (185 + 95) The best bet is keep the chikuni get the seat and throat cut correctly for a 28 or 28.5 intake and call it a day. Also the 14cc heads I do are close to 16cc if they are not milled. One last thing is if you go get a larger intake you can mount the head valve seats up and use strips of emery cloth about 5/16ths to 3/8 wide thru the port an out the valve hole and go in a shoeshine motion to put a radius on the short side brings up low to midlift flow a lot. Also the MCSA of these heads is the interface of the runner to the bowl. Leave runner opening alone but you can widen it just a bit at the last 3/8ths of an inch before the valve bowl and the entry to the bowl. Then you can raise the root and streamline around the guide a bit. Do not get carried away. The runner taper is good for hi lift velocity but when you open it up a little just before the bowl it slows down the air a bit and makes it a bit easier to navigate around the short side.
ole do you have any flow numbers on this head with the 28 valve installed with your porting. you where saying bryan's head might flow around mid 50's cfm. maybe the one big improvement for his application would to install a 28 valve(correct porting) without losing his low mid range power? something he really needs to have for his off-road application.
 
#37
Didn't he say he was going to a TC? If so if correctly set up you can go much wilder that his motor. I am sure (although I have not done it) his head with some work around the entry to the Bowl and SSR radius + streamline around guide and get rid ot the top of bowl step He could get his head into the mid 60's CFM. My 28.5 heads flow between 75 and 80 CFM. Here is a pic of my manifold spreadsheet. carb mani test.png
 
Top