seems as though the alloy heads aren't an issue. which is a good thing. Looking forward to seeing more feedback peoples.

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I am going to list all the faults I have found with my honda conversion.I DO NOT know about the other heads as I have not done any others, so I will not comment on them.
1 the water flow thru head is adequate with the water ports in the head but the bike has air cooling as well.
2 I have so far not had trouble with over heating but as the water pump turns is opposite direction I make a new axial flow impellor for the pump.
3 I strongly believe that the bike head design ie cam brgs etc will not last if they are subjected to contaminated oil from gear box. I now fit my engs with a seperate oil system the lubes the head only.
4 I remove the old cam and drive the oil pump and dist off new cams to reduce extra drag on eng, timing chain wear and possible brg failure. The oil pump is easy to remove and inspect. Extra filters/coolers can be easily installed if required.

As for cam timing the F3 cams [R2] have valve duration of 256 Deg. and opening of 8.5mm.
I have found that the best setting for the cams are
Inlet opens 18 deg BTDC closes 58 deg ABDC
Exhaust opens 54 deg BBDC closes 22 deg ATDC
These settings are very close to a 997 cooper
At these settings the engine idles well and there is not lag in pulling up to max revs.

With the heads air flow is important and when you calculate the area of ID of valve seats the honda is more than a cooper s. The ports are larger and 4 of them. The head combustion chamber is only 10 cc. and that's why I use a spacer plate to get correct comp ratio. I determin the thickness on effective comp ratio[inlet closing point] not nominal comp ratio [max stroke]
The block capacity is exactly same for iron head or bike head, so this does not come into the equation only the RPM that you want to rev to. From idle to your max revs, the eng is going to breath a lot better and your feeding with 4 x 35mm carbs. At any stage of eng rpm the best you can achieve is for each cylinder to be charged with clean air at 14.7 lbs/sq". [N/A]
As for maximum revs it's like any eng build, build them std for 5500 or beef them up for 10,000 and drive them accordingly. I have desinged a rev limiter that works off a tacho with a shift light installed. Use a 2 pole relay , norm open norm closed. The ign circuit is thru normally closed and shift light thru normally open. When the selected revs are reached and light comes on it then drops off power to ign.

Edit Al you have a good sense of humor, I like that, but please join in. any comments are welcome. I am not perfect and you could point out something that I have over looked.
As for me doing stupid things try this one. Engine running and adjusting fuel mixtures on carbys and the little screw driver bit fell out of the socket and disappeared into No 3 cyl. Ask Matt[leema] Now that is dumb !!!!

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

Because it is a twin cam head, both the inlet & exhaust valve timing can be adjusted independently. To do this on an A-series requires replacing the single cam with a new cam with a different profile ground into it. On a twin cam this can be done with an offset key or adjustable (vernier) cam sprockets to maximize peak power, midrange torque, or somewhere in between


And they look cool these are not on a mini

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Too many cars, and too little time.

The cam drive pullys I use are vernier ajustment. The belt pitch is 10mm and the cam can be shifted by 1 tooth which is 15 deg or adjusted with in that using the vernier. The adjustment is with two opposing screws that work against a shoulder on the pully hub.

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

There was the questiom posed back on the infomas Heads section as to how long they will last ... i found this web page a while back from when i first started to reasearch the twin cams and he seems to have been running it for a number of years...

http://www.lojomo.com/

as it states he built this way back in 1989 and put it onto an 850
oh well have a read throgh see what you think
Have a look at the photo where the valve has been touching the piston and the thing still ran

Enjoy Beanie

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I am the son of the STIG

HOTBRICKS
http://hotbricks.org.au/

'65 NCF MINI.....
'69 MINIMATIC.... 9 year resto still on the go

Thanks for that beanie, quite interesting reading. It looks like he has given that eng a good work out. Loved the valve effort.

I do not doubt that these heads will last, but from the contamination problems I have seen in mini eng over the years, it concerned me with the honda heads. A mini rocker gear is cheap to replace, but a whole head because the cam brgs. are stuffed would be expensive to replace.

I might be worrying too much over this issue, but to run seperate lube system with external oil pump is not a big problem. I have even looked at some power steering pumps that could be run off the belt to do the job.

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

So timing can be adjusted into a useable place, good. I would think that this May be a time consuming process, but i guess once it has been worked out for the best results for a specific purpose you wouldn;t change it.

I have picked up the latest miniworld which has a very interesting article in it about the Bimmer hear(what kit I don't know) There seems to be a need to do some pretty serious amount of machining and plugging to the block. How much would this type of work cost as I am thinking it would have to be factored into the equation. They also are using some pretty serious looking pistons that have big cut out's in them. Which bring me to the next question i have been going over. Compression, what are looking at as Std bolt on. I know david has found the compression ratio was way too high and has added a plate to suit. I would think that this would also be helping alleviate the Piston/valve clearence issues. Is this something that the other head conversions are going to need, or will they need cutout pistons.... Again, how much is that going to set us back?

Lots of questions have been answered for me guys thanks. Lets see if we can nut out a few more of them.

Cheers
Aaron

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A few details on the honda head that might help you Aaron.

1 The honda has a centerline dist of combustion chambers of 75mm. centerline dist of std bore 1275 is 76mm. The overall measurement of 1275 cylinders is 300mm. The honda is 298mm
2 head bolts are 75mm longitudinal center dist and across the head 90mm [eqidistant on center line F3 and 3mm offset with F4]
3 combustion chamber capacity is 10cc. The cylinder heads have a wide flat area around the chamber. This allows a variation to seal on blocks of different bore size ie small or large bore.
4 the water holes along front of mini block line up with holes in honda with app. 3 mm overlap. The larger holes at back of block between cylinders again app. line up with about a half hole overlap.

The honda bike runs 12 : 1 comp ratio and the pistons are dome type with valve cut-outs and the pistons are forged. I have looked at using them, but the pistons have a short cut out skirt and would not be suitable for a longer stroke.

With the 1100 engs I use a 3mm thick plate and 1275, 5mm plate for around 10:1 comp ratio. I am currently redesigning the plate and changing the position of the "O"rings so the the water holes on both blocks line up with out re-drilling the block. With this mod the original head bolts holes still have to be plugged but the water holes remain the same. There are 8 new holes drilled along the rear section of block to line up with holes in head. With all the new head bolts the holes are drilled/ tapped to 1/2 UNC and a insert 1/2 UNC o.d with 9mm id. are screwed into the block. The holes in the block are chamfered and the inserts bronze welded in. Some of these holes break into the water jacket so the welding seals them up on top of block. With the plate i use copper fire ring as a head gasket. A honda gasket costs $130 and the copper rings cost $5 each[ 8 all up] total $40. A fullset of "O"rings costs $15

The pistons do require a small cut-out for valves so if timing belt breaks they do not touch v/v if fully open. The small bore engs have a small cut-out in No 2&3 cylinder top to give valve clearance.

With my set-up there is more machining involved ie head/ cam cover line boring for oil pump and dist and the adapter plate. Most of this requires jigs and tooling which I include with conversion. The main reason is to reduce extra cost in duplicating tooling. However if anybody wants to do the whole conversion themselves I am happy to help them thru it.

As Matt said ALL these conversions require some sort of modification, they are not "just bolt on" With any eng rebuild it just depends on what you want and the budget to go with it.

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

Beanie,,, Greg Temkin is his name, we have talked imensly together about the twinkys over the years,,, it`s difficult to work out exactly who was the first to creat it,,, as none of us were on the net when we did it & both of us can`t quite nail down exact dates,,, I expect Greg was actually first, then me not long after by maybe a week or 2 as i had quite a few different cyl heads i was trying out at the time suzuki & Kawasaki inc & finally grabbed the very first Bimmer head avaliable in Brisbane comming from a crashed police bike ,,, even had a fiat twin cam head cut apart to try too (sorry Doc, i know you have a soft spot for them, forgive me , i was quite young then) ,.,,, & then the french guy (Bruno) in around 1996-ish who David talked about,,, but as far as i know Bruno hasn`t made his go Vroom yet,,, he devised a series of gears up the front of the donk, running in oil to drive the cams in a sealed alloy case,,, quite expensive to produce tho,,, w havn`t heard much from him in a number of years tho... Mine was the very first 1275cc , 16v , injected version to run,,,, Gregs was a small bore , 8v, on bike carbys,,, Brunos was a 16v but i don`t know if it`s ever turned a revolution yet.

Aaron,,, sorry so sound like i`m harping but most of this info is all over the net,,, Many many places, many many sites have plenty of write ups,,, please have a look around at sites like efiminis.com & turbominis.com 7 the like,,, & if you`d like to just surf over to one of my web sites ,,, specifically This Page--->

http://www.users.bigpond.net.au/TheMiniMan/page2.html

It will show you most of what you need to understand how one of these go together,,, however this is only showing the 2nd version of how we did it,,, we have refined the kit far more since those days, but the basic ducks guts of it remain & only a few fiddly changes to make them neater, & less complicated

if you`d like to actually learn more? then i am approachable via PM or e-mail & i also have a build guide which explains more than twice as much as any other bimmer twinky build guide on the planet ..,.& is well & truely up to date with the latest info on both small bore & big bore Bimmer twinky building info.

I`ve also been playing with a 20v, R1 yamaha cyl head to go onto a small bore mini donk since i bought a few engines for my hillclimb special

edit--> Oh & the article in the mag is engine build by "MiniSpeed" & they actually used Jon kimmins (Specialist Components) conversion kit.

sorry to butt into your thread David,,,, I`m attempting to be civil & informative & not sooking any more continue at your leisure please

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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.

Thanks Guys all good info.

Matt, i understand it may be all over the net, but i think it would be good for it to all be here in one place on Ausmini. I only look at Ausmini as i am sure hundreds of other Ausmini users do. It can;t be a bad thing to have it all here rather than having to use info from many different places. Can't be a bad thing can it.
I'd be happy to read your build guide Matt. It would be interesting reading. Is it something you would be willing to post up here or would you rather email it?

David, and Matt, In regards the machining that is required on the block, How much work would be required and is it at all possible to reverse engineer it back to a std 5 port head block? May sound like a silly question, but i think some people like me, would take it into consideration. 1275 blocks are getting hard to find as people are hoarding them. not such a concern for small bores, but still worth looking into.

Cheers
Aaron

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Aaron,,, as much as it would be all nice & wonderful to have all the info you or anyone else needs, right here on ausmini,,,,

it`s called -->click the button onto the links already given"

if you had looked at the link i just gave you, you will be able to plainly see this photo-->



see all those little rings where some of the old mini holes have been blocked/plugged up??? & see where the new holes have been drilled & threaded for the Bimmer head???

most cyl head conversions require some form of modification to the top of the block

well you`d have to re-do all that over again to bring it back to the mini bolt pattern & water passage & push rod hole again ,,, """IF""" for whatever reason you decided that you didn`t like the Bimmer (or whatever cyl head conversion you chose)

Now,,, it`s not a big job to modify the blocks to make other cyl heads fit,,, as much as it may seem to some people,,, it`s all pretty normal for any decent engineer or engine reco shop to do,,, & would cost approx $200-300ish .... However,,, i find it hard to understand why anyone would want to return the block back to an ancient design cyl head after doing all that work making such a good cyl head fit it ??? sorry but really???

there are litterally thousands of mini engine blocks , all over the place, there are plenty of them everywhere... it`s harder to find good cranks shafts than engine blocks

The idea isn`t to try a cyl head conversion & if you don`t like it then change it back mate,,, You`d have to have rocks in your head ,,,, if you want to try one out then just wait a little while & you may find your self sitting next to one at a mini show or at your local mini club meeting & ask the fella who owns if to take you for a spin

sorry ,,, i really do find it hard to believe that you wouldn`t just have a little click around other mini web sites & see all the info avaliable.... but you say you only click onto ausmini & that`s it,,, no where else at all???? ,,, i really do find that hard to believe man... really!

that`s like having a swimming pool but only sitting on the edge of it (with your eyes closed) with only your toes dipped in a little bit mate,,,

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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.

Matt, I did click on the link and i did read it all.....
BUT, really, I don't see why the questions can;t be asked here and answered here. that is what this forum is all about is it not? I'm not expecting anyone to research for me, but we have two members that are into conversions. You included. Why not ask, who better to get the answers from but the horses mouth(not that i think your a horse)? That way when in future when people search they will find ALOT (but not all) of info and have MOST of there questions answered.

The info you have provided is a big help for me, and I'd like to think that the info is also very useful to many other people that are interested.
But, if you think I should be quite and not ask, I can do that if you like.

1275 blocks are getting hard to find at a good price down here. Up there maybe not, but i agree cranks are like hens teeth.... I am still searching for a large journal for a stroker motor I intend on building for my 'S" later on in life. One will turn up at the right price.

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It`s quite interesting that you use the words "Std bolt on"-----i don`t know of many "Std Bolt on" cyl head conversions,,, the KAD heads, the Jack Knight heads, Elder heads & Arden heads would have to be the closest to "Std bolt on" than any of the others, but still they all need some forms of modification to fit them "Correctly" & have them running well,,, & all are very expensive propersitions... there is no "Cheap, bolt on" wonderful amazing cyl head conversions avaliable,,, they all need some form of mods & all need more money than a std 5 port engine to build.

The Bimmer 8V cyl head has a combustion chamber capacity of approx 21.5cc,,, so is well suited for fitting to a mini block with just fly cuts needing to be machined into the tops of the pistons,,,

the 16v head has approx 28ccs in it`s chambers so makes for a slightly lower compression with std-ish pistons, however it`s easy to just use flat tops & have the fly cuts machined into them & deck the block to the desired height to suit whichever applcation (high or low compression),,,, that`s your choice -->no matter whatever engine you decide to build.

it`s also interesting that you use the term-->"Serious Pistons" ... but they`re not needed at all , unless you`re thinking of going full race or high boost turbo application,,, but that rings true with any engine tho, be it twin cam, 8 port or 5 port, so it`s not really an issue at all & is std engine building practice to have all this worked out on any engine before it`s built to make sure you don`t have too high, or too low compression to suit your application, & or any part of the piston hitting any valves,,, it`s quite normal for the engine builder to sort all this stuff at the first "DUMMY" up of "ANY" engine,,, again it`s all std engine building practice no matter what engine you`re building.

the fly cuts into the tops of the pistons cost appox $150 to do, depending on who does it for you if you can`t do them by yourself..

What is also interesting is that there are very very many web sites that list most (if not all) the mods needed to suit all their various forms of mods needed to fit each of their own cyl head conversions

there are also build guides avaliable for most of those too, which explain in great detail most of these conversions

Davids conversion s still in it`s infancy & what a wonderful thing he`s doing i might add,,, allowing all the world to see what he has achieved so far via the net is truely wonderful & his time is most valuable & his information is spreading over the net,,, as is another fellas own conversion using a fiat punto single cam 12v turbo charged with LPG , just yet another example of what any one can do with a little thought & a little home work

MY R1 yamaha 20v cyl head (if/when it comes to fruit) i hope to be yet another example,,,

but some of these conversions just don`t quite have perfect accurate detailed info avaliable at this stage of their development, not many people will happilly devulge all their info either.

I think it`s just wonderful how much info is actually shared tho, all around the world, via the internet ,,,,& how easy it is to click on & find it all....

Don`t you?

It`s just amazing how easy it is these days,,, back when i was a kid we didn`t have any of this avaliable to us & we had to do all our homework by our selves & sort all our curiosities by both theoretical & physical trial & error:-) physically running all over the place to all sorts of car & bike wreckers measuring & facing up & buying all sorts of things , just to see if we have something close to fit.

an example here would be the old 4 cyl motor bikes used to have a centre designed cam chain assy , (fitted in between number 2 & 3 cyls) so it made it very difficult to adapt one of those old design bike heads to a mini donk,,, but as soon as the end mounted cam chains appeared in the 80s(ish) there was a golden opportunity for some "Play time"

Not many people realised it back then but there were a few who did & took advantage of that,,, but it`s taken years of playing & many many hours wasted sorting all the possibilities,,, yet here we are finding even more & more cyl head conversions avaliable to us... because some lovely people have spent their valuable time & money soring it all for us

i think it`s just a dam good all over wonderful feeling Don`t you?

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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.

hey that`s just your opinion

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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.

Some people describe me as a sloth, it takes me time to do anything, and to digest things, unless it's beer, i'm good at that

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