K-series conversion
Turbo Mini Forums

Hi guys, anyone can direct me to some good reads about the k-head conversion ? I recently bought the SC components guide, but before I start purchasing parts I need to know for example the main differences about the k1100; k100 and k1200 and maybe the difference between LT cams and RS cams. I tried using the search button, but I haven't yet succeeded in finding a good theoretical thread yet.

Thanks in Advance

K100 is 8v, and has 285ish degree cams,

K1100 is 16v and thually comes with the LT 255 ish degree cams, somtimes you find the RS cams but fairly rare,

the K1200 is basically the same as the 1100, some minor casting differences that you dont need to wory about, main difference is they have thinner valve stems (6mm) so flow a bit better and rev higher, normally come with the RS cams 285ish degrees. the 1200RS also has slightly larger throttle bodies.

It tells you in the build manual about the difference in cams. As Joe says there's the 256 degree LT cams giving 8mm of lift and the RS cams 285 degrees and 8.8mm lift iirc ?

Phil.

WWW.TURBO-MINI.COM

So I guess the LT cams are better for a turbocharged application ? With regards to overlap

yeah generally thats the case, also as the 8v only comes with the long cams it sorta rules it out a bit for turbo.

obviously you can spread the lobe centreline to reduce the overlap, but theres a limit.

Turbo Harry tried the long cams and didnt like it, i belive he ended up with the LT intake and RS exhaust cam.

http://www.minifreunde.at/harry/links/startup.htm

So the head has been bought :) I went for the K1100. The plan for now is to use the standard 81mm crankshaft with 71.4mm bores, just to start with. When the engine runs fine and I get the hang of it, then I'll start worrying on the bottom end. Also this helps to spread the total cost over a longer period of time.

My concern now is what type of timing gears I should be using. To be honest I wish to most of the work myself, as the main aim of the build is to learn something out of it. So basically, I'm having the head dry decked, but I will try to machine the end plates myself, as well as the block conversion. So for starters I need to sort out the timing gears. What are people using ? Apart from buying the kit from SC ?

Buy it from force racing... they might sell you the individual pulleys if you ask nicely???

Hi guys,

Just a little bit of recap on the build. So the head arrived in the past couple of weeks. It has been dry decked by SC.

I'm following Matty's route in trying to build the kit myself to reduce on expenses as much as possible, and also learn some machining techniques along the way.

I'm now in the phase of thinking about the bottom end. Initially I was inclined to go down the short stroke route using a 12G2827 crank. I must remind that the engine would be turbocharged.

Along the way to reduce on the cost I began thinking to scrap the idea of short stroke and instead use the worked 1275cc crank.

However now that I'm looking to buy the forged pistons needed for the turbo I'm rethinking of the short stroke idea. I guess if I go down the short stroke route I might end up not needing the valve cutouts in the pistons. What do you guys think ? Any 16V short stroke builds in here ?

The idea of running the pistons that far down the bore is not really the way to go about building a high performance engine. Sure it will work of sorts, but it won't be all it can be. The squish area of the piston is an important area for detonation resistance, and you won't have that running the pistons that far down the bore. Also remember that less cylinder CC requires a smaller combustion chamber total volume also. You really need to run the numbers and work out how you are going to achieve the total combustion chamber volume for the compression ratio you intend to use, which should be somewehre in the region of 8.5 or 9.0 to 1, maybe even higher.

Have a look at Gr4h4m's short stroke project in the show us yours section, although it's supercharged, it'll give you an idea of some of the complications involved in using a short stroke crank in a standard stroke block.

Edited by Sprocket on 10th May, 2017.

???
You will always need cutouts in the Pistons unless you intend on leaving the pistons way down the deck face, which is as much use as a chocolate teapot.

yep as above,

i build with my pistons in the oprder of 5 thou down the block.

look up squish band.

You guys were right I had a miscalculation in my excel sheet. So the idea is scrapped.

So what CR do you guys recommend for a turbocharged k1100 ? On my 998cc I'm running a CR of around 8:1, with around 15psi.

Now with the K-build I wish to top up the boost to around 20psi, what CR do you favour ? And are there any cheaper options than going for the forged 18cc omegas ?

Aim for about 9:1 don't go lower than about 8.5:1.

Cast omegas wan be dished out a bit, so would probably get you where you need to be.

Cast Omegas seems to be 10cc greatest. Do you think they can withstand the 9:1 and 20psi ?

With the 10cc as you said they need to be dished out slightly to get around 15cc. Is that achievable from a 10cc piston ?

The k heads can run a lot of compression. I'm sure Matty is running a ton of boost on a decent cr

Have you measured the chambers in the head you have ? On the one I'm currently working on the chambers are actually 2cc bigger than the figure quoted in the SC manual.

Phil.

WWW.TURBO-MINI.COM

No to be honest I haven't Phil, the reason is that it is still dismantled. However it has been resurfaced, so ..

Ive gone a slightly different route with the timing end. (I was extremely broke (house buying will do that), but wanted to play anyway, so bought a k100 engine for £50) Using a set of saxo vts pulleys (cam pulleys are split from the factory, so cheap/free verniers in real terms) adapted to fit the cams, and machined both the a series bottom sprocket and the saxo bottom pulley until they fit together perfectly, then pressed and dowelled.

I figured the belt side would be easy, as all cambelt are either round tooth or square tooth..... this was wrong, but some several hours scouring through a massive collection of cambelt books led me to a few cars which share the correct tooth profile and spacing as the saxo, coupled with a very friendly motor factors who humoured me and ordered me all of the possible belts (about 4 iirc all +/- a tooth or two) and allowed me to return the wrong ones saw me fitting a volvo 940 turbo cambelt (5371XS) which coupled with a adapted ford tensioner (either pinto or zetec, cant remember) seems to work fine.

I got to that stage fairly quickly, then work went mental, and the project got mothballed, and life took over......

It will be dragged out soon(ish) to finish. Ive recently taken the actual car home to sort, and the engine will run as a sort of lunchtime side project, so hopefully byt he time the shell is all complete ill also have a k100 turbo headed engine to drop in!

If I was starting again now, i wouldnt necessarily go the same route, but my time/finance ratio has changed a little since i started the project. Ill see it out and finish it off in this current route just to be bloody minded, but will probably try and track down a 16v head to swap out for the 8v one at some point. we shall see. in the mean time, ill be reading as much as possible to try and speed the learning curve up!!

And on the 7th day........... God created turbochargers!

With regards to the timing side, I think I'm doing quite good. I took Matty's route and doing everything by the tools available at the garage. I will post some pics as soon as I have them.

But it seems the piston/crank assembly is a little bit tricky to get hold off at a reasonable price . I don't wish to opt for a 73,5mm pistons due to it being forced induction. And that is one problem right there, because MED only supply pistons with cutouts for the 73.5mm pistons.

So I have to buy +20 or +40 pistons and do the cutouts at a machine shop. And the cutouts alone cost around 100eur.

Furthermore the other problem is that I recon that with +20 and std stroke, I need around 15cc pistons to get around 9:1 CR. Now the only omegas with that kind of cc's are the forged 18cc pistons which cost 500gbp.

It seems like cast omegas go up only to 10cc's. And I'm thinking that to scrape off 5cc from these is a little bit greedy ??

The only pictures I have so far:

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What pulleys are you using, to me the timing plate its to thick, I ended up using only 10mm.

I´m also building a "low cost" k1200 conversion.

The pulleys are from SC.... yes you're right the plate is thick, but I'm facing it off to 12mm. It is currently being machined

Today got the upper plate machined for the oil seals :) :)

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Next step is buying a worked crankshaft, and the pistons, whilst machining the bottom plate