BMW head on a 1460?
Turbo Mini Forums

Hello folks. It's been a long time since I was on here. I was last messing around with a 64 Mini Minor with a BMW blower lashed up. I'm now running a 66 Morriscooperish which has an ex-autograss engine in it.

320/320 cam, 1425/84mm, old fashioned race head....massive ports (sleeved rods) and quite small exhaust ports. Weber 45 on a 7" manifold. I didn't like the crank, as it wasn't sufficiently worked and pulled it out and got rid of it. I have picked up an 86mm EN40 forged crank with all the bells and whistles. I'm probably going to get a set of SC H rods and a set of new pistons (short comp). Since the bottom end will be so good, I wonder if restricting it with my old head would be such a bad idea.

This got me thinking about the BMW head and whether all my old stuff would part out and pay for a lot of it. Since I'm a shed tinkerer, I'd like to do a fair amount of work myself.

I note that SC sells a variety of kits and I'd be quite keen on the basic "do it" kit and potentially modifying the head myself.

I've emailed SC, but have had nothing back so far. I thought I'd rejoin you lot and pose the question and see what you thought.

I'd like to pose a few questions to the turbominis collective genius.

1. Am I right in thinking that the K1200 head is taller than the K1100 head?

2. Are the K1200RS cams more cammy than the K1100RS cams?

3. Will the head have enough holes in it to allow a 1460 steel bottom end to run to it's full potential, or am I likely to need some different cams and bigger valves?

4. How much meat have you got around the ports to go hacking into?


I'd be grateful to hear any of your input, or alternative ideas. I might slightly entertain the thought of a 7 port. The car is not a daily driver and was formerly pretty much a road going racing car. I'm not bothered about very bad road manners. It's all about the bang per buck.

Stu

Howdy,

I'll try to answer these in order,

SC are a bit hit and miss with their emails, unfortunately thats often the way with these companies, they start out good and get overwhelmed on the communications front.

Its all well and good doing the conversion yourself, but bear in mind that for the SC head conversion price you get the head cleaned, and put back together, so all the valves reshimmed if needed, if you have to start reshimming it starts to get expensive.

1) the K1100 and k1200 are the same height, the cam cover differs, the 1200 has a magnesium one, that may be the source of a few mm more. the only differences are, a different oil feed arangement to the cams, the cams ( hotter) and the 1200 has smaller (6mm) valve stems.

2) yep, the K1100LT has 256 degree cams, the K1200RS has 284 degree cams. you can swap them... but ypur looking at re shimming again. there may be some oddballs floating around with the different cams, but the above rule covers vertually everything I think.

3) yeah, a std 16v K head will be similar to a very very good 5 port, SC do some good head work on the K, ( i think its actually done or developed by Schloar race engines) theyve built 160-170hp race engines based on 1380, and recently put together a monster 1460 with BIG ports, if you do facebook theres some picks on their page....
https://www.facebook.com/media/set/?set=a.1...56335284&type=1

4) a fair bit, John from SC put up some pics of a sectioned 1200 head a while back (see below), but I would say, the real benifits are iin the seat area as with most heads, if you rip the ports out bigger you run the risk of screwing up the port velocity.
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=184839

in terms of 7 ports, I like the SC one, it certainly works well, wilh on here has been hilclimbing an SC headed 998 that makes just shy of 180 hp on 18psi boost. I myself ran a turbo'd minisport 7 port, which was ok, but a tendancy for the valves to pinch in the guides. the K heads so much quieter when ticking over, no pushrods rattling about.. thats sold me on converting.


oh, if your going SC rods, look at the 6" ones, if you can get the pistons short enough deck height to use them it will make a nicer engine.

Cheers Joe.

I'm also factoring fuel into this. The 5 porter is a bad manners engine and does about 12mpg. It's also leaded. This does add up.

I have heard about the 6" rods elsewhere. This sounds worthwhile.

Thanks for the link to the sectioned head. Very interesting. Not much to be done at all. I like the idea of the thinner stems of the K1200RS. I suppose 3 angle seats and that's probably enough.

I'll have a look at getting a head and if one doesn't come up at a sensible price, I'll stick the 5 porter on it.

I'll start hunting for a head and the bits.

worth a mention...

the 1200 is a bit rarer, the 1100 less so but they do comand a price...

the K100 8 valve often comes up cheap and is still a good head, they make about 110hp on a 1380 with no port work. they also have 284 degree cams.

also worth you looking at if you like a project, is the fiat 1.2 head, robert on here had a lash up of one running.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=222255

What sort of prices are we looking at for the BMW heads? Ebay is a much of a muchness and forums bring up stuff from 10 years ago. I'd consider buying a bike and stripping it.

It seems there is a lot of money on people buying them and parting them out.

The fiat head looks tall.

If I can realistically flog my head (v nice) and all the associated bits for it. 320/320 cam, modded dizzy, 45 on 7" doweled, etc and get a head and some of the conversion kit price, I'll do that.

k1100's go for about 350, Ive not seen enough 1200's to get an idea of price,

ironically you can probably get a whole bike for vertually the same and part it out.

the K100 more like 150,

yeah fiat head is a bit tall, but itn seems it would go in, IIRC the later cam cover on the fiat 500 looks like its smaller.

Ive got a k1200 on a 1450 bottom end. Goes well!

All i did was fettle the ports to remove the obvious casting marks and that sort of thing. The most important bit is blending in the valve throat around the 'short turn radius' its not a very good shape as standard and thats where you can gain alot in most heads. My motor is not race spec so you could go further but unless you have money to burn i dont think its worth it. I think the key to getting the most from these heads is getting your engine to rev. The cams are good to 8000rpm or more which is too much for my current setup. Sounds like your more in that ballpark!

Hi Stu, I'm a keen tinkerer too and love a challenge, I went for the bmw conversion and decided to make all the required parts myself, it's a major engineering project but very satisfying on the day you finally fire it up. I liken the conversion to when Cosworth did the ford pinto and created the awesome YB engine in the late 80's.

an excellent write up by joe hear, he says it all

This has convinced me to actively seek a K1200 head.

My whole suite of 5 port stuff will be on ebay in due course.

Be sure to do a build thread. Sounds like a good project.