In simple terms, you grind the other side down. This makes the hump bigger.

Hi Dave
Yes this head will be better but how much we dont know yet,
we made 245hp on a 5port on 15lb boost.
HI Mick
Most bikes these days have over head camshafts very light valves
and running gear no push rods to flex and heavy rockers to control
and big bore short stroke, made to rev
Graham Russell

hee hee,,, thanks GR & i must say you really are taking to this computer technology thing quite well,,, pics & posts & data,,, well done becarfull tho,,, next we will see you all set up with your dyno hooked via direct link into the web

sgc,,, Morris1100 is right (((To a point))) you can only really (sucessfully) grind the base circle of the cam down so much,,, Most "warm" or hotty road/rally cams can be ground down & (in the process) re-shaped, to affect a different profile/characteristic,,, usually allowing more lift &/or duration.

But if a "Decent" full race cam is desired then it`s best to use a 'Billett", (a blank) which is effectively a piece of solid round rod or bar that is then ground down & shaped into a cam shaft,,, machine the lobes & the gear drive for the dizzy etc,,, harden it & away you go (sort of thing) this way you can obtain a much wider lobe (poor choice of words but still) for longer duration & higher lift is avaliable this way too, without loosing any of the std original base circle.

Welding a std-ish cam up (adding material) is another way of making a bigger cam (egg) ,,, the welded part is often harder than the original cam material (in most cases) & can be good in the respect that the main part of the lobe that cops the heavy treatment/pressure/wear (the top half) of the lobe is pretty dam tough on a welded cam,,, but often it`s the section where the weld starts (the ramp) that can "pit" up or peel or start disintergrating if the weld hasn`t taken very good, or if the profile that`s chosen hasn`t been designed or ground very well,,, it`s that part that is normally really taking the beating,,,---> the ramp up,,, the steeper the ramp, the more crap/pain it cops.

hope that goes some way towards helping you understand , there is obviously way more involved with cams & all the different ways things happen & it`s often called a 'Black Art" , so i`ll leave any more detailed descriptions & explanations to GR & David R & anyone else who cares to add their knowledge into the pot I know what cams i have used & what they`re like,,, i`ve compared many ,,, i`ve read up heaps ,,, My dad was good mates with Ivan tighe (obviously still is) & i grew up watching them "Play" designing & making new profiles, borrowing other profiles from other manufacturers & generally trying new things,,,

I had one major benefit in all that where i was able to directly compare all these cams with the seat of the pants, driving the minis they were all fitted into There`s nothing much better than "Feeling" the differences & comparing the stop watch times, in a swag of cams in a pile of minis running at over 8500rpms at places like under the Dunlop bridge at Surfers paradise raceway & Lakeside raceway etc etc , doing lap after lap,,,, tracks like Morgan Pk (when it was dirt) Stanthorp, Dalby, Millmerran, Echo valley (also dirt & also my mosr favourite track ) Speedway tracks all over the place,,, Hillclimb tracks & Autocross tracks all over the place,,, all through my chldhood & intoadult-hood (I`m almost grown up now ) & having a "Play" with different profile cams in the same engines to help gain that edge , get extra grip & drivability etc, (depending on the circuit),,, dirt tracks offer & demand differnt circumstances, needs & approaches to gain that edge,,,, having that experience is what really opened my eyes at the relative "major & minor" changes in a cam designs/profiles,,, it was some wild times back then,,, & just an example of why i keep on about "Horses for Courses" all the time... to me it`s the most important part,,, well most important after the 'having fun" part anyways


I`ll shut up now

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

That's what I thought, to gain extra lift.. but you wouldn't be able to modify the LCA or duration from the donor cam very much this way, surely?



Did I read somewhere that billet cams for the A-series were NLA new any more? In any case, I'd imagine these would not be cheap...



This is what I imagined could be done, but I have a vivid imagination sometimes

_________________
Simon

The adventures of an owner builder in the Tallarook Ranges

Hi SCG
I can grind a good std cam not worn to much into a full race grind
and change the lobe centres down to 102-101 from the std of 108
and give it .350tho lift on the lobe
Graham Russell

F3's

F4 race replica

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Hi Matt
The posts are ok but when it comes to putting up the photos a song
comes to mind sung by the BUGS i think
I GET BY WITH A LITTLE HELP FROM MY FRIENDS if you know what
i mean.
DAVID
Like i said too much valve too much port BUT what about that
head on 970 bottom end bored to 73mm (same as most of
the big bikes) and let it rev could be exciting?
Gota do some work now

Graham russell

Yeah GR, it took me a while to learn all this posting photo stuff too,,,

& David,,, hee hee,,, You`re almost a better pot stirrer than me

& GR,,, you might actually be starting to see what i`ve been on about with these Twinky heads,,, good for you My race engine is 1070 (Sth African large journal crank) bored to 73mm with Twinky head ontop, T28 turbo & all the injection stuff should scream to 10,000-ish,,, add 30lbs of boost & act just like a Slot car i reckon

(Am building 2 of them just so i have a spare when the first one goes bang)

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

how about a large journal 1100S crank de-stroked to 78.3mm - with 73mm pistons it's nearly square... and makes 1311cc - that's what I want to do (one day)

_________________
did I tell you that I won a trophy?

Simon,,, i`ve chosen to use the very short stroke Sth African crank for my race engine, for a few reasons,,, one is that it is (Possibly) the strongest factory crank avaliable, the Sth Africans have been known to take these cranks to 10,000rpms ,,, 2ndly because i have 2 of them,,, 3rdly because with 73mm bore & that stroke i can legaly twin cam 16v turbo charge & inject it & keep my sports sedan engine within the Under 2litre class regulations

we have lengthened the stroke on std issue 1275 large journal cranks with 73mm bores (1412cc) since they were first avaliable (1969-ish) & have had no trouble spinning them to 8000rpms for very long periods & for many many years, so "If" you treat them the right way when de-stroking then i can only assume they will be fine too

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

A Series please 12g940

You`re not really going to see "what you really need to see" via a photo or 3 on the net,,, to """REAL:LY""" inspect a cyl head to get the entire, or whole, package of design involved then it`s going to take a physical inspection with a very experienced "A-series" cyl head guru,,, going through the whole process with you, determaning exactly what sort of power you want, & where within the rev range you want it, & what sort of engine characteristics you are after & ontop of What motor to suit... sorry this sounds like mumbo jumbo, but thems the facts,,, Unless you get a series of plastic (or cardboard) port shaped templates & a whole pile of depth measurements to stick to & use as guides to give to who-ever ports your head for you,,, & even then that`s really a fumble-arsed way about it all these days

Not much has changed in physics of port flow & chamber fill characteristics over the years,,, Visard wasn`t far off the mark (only occasionally) It really is all simple common sense & physics, just some minor adjustments to suit the differing cyl head & engine design criteria,,, if you`ve done a cyl head to Visards recomendations then it`s probably going to be "OK",,, he wasn`t "That" dumb

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

DAVID
Like i said too much valve too much port BUT what about that
head on 970 bottom end bored to 73mm (same as most of
the big bikes) and let it rev could be exciting?
Gota do some work now

Graham russell[/quote]

Its been done by a bloke in belgium I did a F4 race replica head for.
72mm cbr 1100 pistons in a 1275 block with a billet 60mm stroke crank , billet alloy rods, 4 bolt steel mains and dry sumped.
Over 10,000 revs and around 160 at the wheels.



The original eng set-up had modified 940 head but he reckons this accelerates much quicker and has heaps more torque.
I am waiting for him to send a video of the thing on the dyno once he has all the bugs sorted out, clutch and driveshafts.

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

I am not stirring. The blokes name is Johan Brocke and his brother stefan run a engineering buisness.
As you can see it is road reg and he drives it around Ypres where he lives.
He has at least got one running in a car, I haven't yet, but is good to see.

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

So for a 1360 eng these heads would need mods to reduce the ports and valve area.

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com