If you don`t really want to learn how to do all this,,, &/or don`t want to spend the years it takes to learn how to swing a die grinder inside a 5 port A series cyl head without wrecking it & starting again on another, & another & another to gain the first hand experience working out what works with "Your" engine & what doesn`t,,, & what works with "His/her" engine & why it doesn`t with yours,,, & vice versa,,, but you still want a dam good flowing cyl head that works extreamly well at & throughout all revs (low, mid & high) then just buy one of my twin cam motorbike cyl head conversions :-)

I have this theory that excess weight is horse power lost,,, fair to say yeah???

Therfore suffice to say that if we removed all 4 road wheels then the car must of course become faster , right?



For my own personal race head i use ex-Indycar titanium test valves, thin the stems down & trimmed down heads to 36.8mm for the inlets & 31.4m for the exhausts (i also use motorbike valves in some other race heads)

my own offset guides to suit

1.5 rockers

very broad short radius on the inlet port area as it encroches into the chamber,,,, barely touch the peak between the inlets in the siamesed section & only to help round it off gently,,, CAUTION HERE!!!--->if you sharpen this peak you will then creat hollows & swirl-pools in the areas either side of the peak , effectively creating smaller pathways into each inlet valve at the siamesed section... much like a sharp edge at the mouth of a carby does.

Obviously de-shrouding the chamber around the valves is of vital imoprtance to chamber filling characteristics & gass flow, so this should go without saying but is often either overdone causing head gasket issues,,, or left without enough attention to detail.

I reduce the peak in the chamber quite substantially but don`t remove it completely,,, the theory is simply so the head doesn`t crack there, as they get quite thin in that area & also to leave a tad there in an attempt to help push the gasses or help prevent the inlet gasses running straight across & out the exhaust hole during overlap period,,,, i also creat a dent or gully (for want of a better description) at & around the spark plug, more like a broad depression from the inlet valve in a gentle arc past the spark plug & across to the exhaust valve,,, those last 2 modifications tend to cause an action much like "Sheep-through-a-gate" in that once gasses start moving in that direction, then more will follow the same path... Again , simply a small mod to aid the direction of flow against running gasses straight across & out the exhaust valve in turn helping to fill the chamber & creat a better flame front & direction of flow.

I also try to shape the chamber more like a rounded bell shaped bath,,, sort of hemi shape if you will,,, & yeah i know it`s impossible but i do the best i can as it actually does creat more grunt & better squish.... & obviously pollish the chambers & at the same time (while pollishing) i make them all the correct & same size to suit the intended application.

Inlet port work should be aimed more at "ANGLES" rather than size,,, it`s far more impotant to utilise the direction of flow than the size of the hole... EG:--> If we took a std-ish 1275 cyl head & looked at the inlet valve size (33mm-ish),,, then we take a few mm off for the valve seats widths ,,, then we take another 7mm off for the valve stem,,, well we only end up with about 23mm-ish across,,, so you can all work out your areas from that but it isn`t much hey???,,, so what`s the point of making the inlet port 50mm diam when we can only use 23mm diam at the valves area??? Got that???

The valve seat area is the most important part to work , you want to "BELL-MOUTH" it (people tend to use 3 angle valve seats but it`s more to get them into the shape of a rolled radius or bell mouth than any speical series of sharp edged angles,,, got that??? & please don`t make valve seats too wide thinking that you`ll get a better seal,,, wider seats don`t last as long, but too narrow & they will over heat,,, there`s a "Just-Right" width for all different applications.

& even just prior to the valve seat area it`s good to get rid of some (or all) of the valve guide boss,,,, but i try to leave a small shaped up-peak prior to the valve stem to help to "start" to divide the gasses before they just simply smash onto a round valve stem,,, so getting rid of the guide boss completely isn`t often the best thing to do,,, get it???

OK<<<OK<<< so it`s not "ALL" about avaliable hole diameters or lack of guide bosses,,, we can all say it`s more about the area of the hole avaliable yeah?,,, well yes it`s that but it`s "ALSO" got to do with what`s called "Valve Curtain Area" too,,, lets just picture the valve open fully to whatever the cam & rockers give us...ok? then lets pretend we have made a little shower curtin all the way around it , now measure the area of the curtain used,,, easy really hey?,,, valve diam in half,,, then meat pie x radius squared = area of hole then x length of curtain = valve curtain area right? good ,,, you`re getttng the picture with avaliable space to pass gasses through now, sweet, that`s one big chunk of wonderfullness understood yeah?

But it`s all not just about what you can cram in there at full valve lift either hey????? there`s way more than just a few tricks at full tilt,,, we need to get as much gass as we can, all moving as fast we can, as early as we can... & physics is the name of the game here... there`s a big package of the sh!t to think about.

Now,,, the point i was getting at a bit earlier is more about the "ANGLES",,, so,,, if you look into a mini cyl head inlet port,,, & take a one "side" view from the edge of the port & run your eye down that first angle on the side of the initial part of the port & line up the flat section or align it`s "Runner" , you`ll see it roughly points at the peak inbetween the 2 valves in the siamesed right deep inside the port , yeah???,,, well most cyl heads have their runners aimed at landing gasses (or pointing that side of them into the direction of)behind the peak & hit it before the opposing valve,,, we would much rather it land almost right on the peak of the peak but with a tendancy to land it just after & just a tad into the opposit side of the peak to help direct gasses over that way & not hit it before the peak,,, same with the other side of the port,,, so in effect we can pretend we are "crossing-over" our gasses & aiming them from one runner on one side of the port over to just a tad on the other side of the peak... there`s quite a few dam good reasons why we want to make these angles work for us, but if i typed all about the whole lot right here, right now then i might as well type a whole dam book about it all & i`d be here all night ( & the next few weeks)

BUT!!!!!!!!! if we made the smallest part of our inlet port (about an inch or so inside the head) too dam big, then we`d need an even bigger entry hole at the mouth of the port to keep that alignment ,or runner, aiming at our peak yeah?,,, imagin it, or even better still, "Draw" it on a piece of paper & you`ll be able to work out how big you can go in reality,,,it`s quite common to open the port up so big that they break into the push rod holes & we can simply sleave them & go again,,, narrow down the tips of the push rods so we can get them back in their holes when building the engine, yeah??? easy hey?,,,, but in reality , we can only go so big untill we loose that decent angle,,, & a "Massive" inlet port is just "NOT" what we need , nor want, especially on a road engine

Road & race heads are 2 different kettles of fish , so don`t confuse to 2,,, but in general we can try to blend "some" of the stuff we do on race heads into our road heads ,"WITHIN-REASON" ......& if you don`t go stupid with sizes loosing your angles in the process,,, well maybe you`ll end up with a half decent cyl head

now that`s a dam good start for you all if interested in "Playing" with cyl head porting,,, there`s a whole bunch of other techniques used to good effect & there`s a whole bunch more that can be done in other areas too,,, but i`m not going to part with all my little tricks & secrets

If you don`t really want to learn how to do all this,,, &/or don`t want to spend the years it takes to learn how to swing a die grinder inside a 5 port A series cyl head without wrecking it & starting again on another, & another & another to gain the first hand experience working out what works with "Your" engine & what doesn`t,,, & what works with "His/her" engine & why it doesn`t with yours,,, & vice versa,,, but you still want a dam good flowing cyl head that works extreamly well at & throughout all revs (low, mid & high) then just buy one of my twin cam motorbike cyl head conversions

A true salesman to the end Matt Love your work

I want Dyno results ATW or Crank

OK... leave off with the hairdryers, I've seen a 5 port iron head with turbo give 240HP briefly.
What HP do these heads make on an N/A Mini, or gimme some airflow figures...

The only thing that i can see & undestand is that with any given 5main bearing engine , there would be """more"" losses or drag with the extra 2 earings as compared to a 3 main bearing engine