Advice on BMW K cylinder head conversions

[Nathan1293]

Hi everyone.

The background to this is I have two MK1's both 64 B plate cars.

One is a 998 Cooper and will be going to standard restoration.

The other is a bitsa car. Ideally I'd love to run a KAD 16v, but that costs too much (at least for now).

I've run heavily modified 5 porter before, which was great fun. But I don't want to cut another webber airbox in the mk1 shell. So a BMW K head conversion seems like a good option.

I know this forum may not be the best one to ask, but there doesn't seem to be a great mini forum for this (16v forum seems more interested in engine swaps).

Anyway, I intend to make use do a conversion myself. Does anyone have experience of this conversion?

I've seen two great conversions (not sure if I can link to these here, as I don't know this forum etiquette), one by Sprocket/K1275RS (was based in Warrington I think) on some forums where he offset bored the cylinders then relined to get equal cylinder spacing. Which looks like a great idea for many reasons, not just aligning the cylinders but also reducing crankshaft whipping.

This idea has really caught my imagination, and seems like the avenue that I'll take. I'm intending to run +20tho overbore so should be fine and not a 1380.

But if anyone knows this person or has any advice about the conversion. What worked well and what didn't that would be great. For example hotter cams than the RS cam, larger inlet valves or just general feedback.

Machining is not due to start until the autumn, so plenty or time.

Many thanks

Nathan

[Richspec]

There are some builds on the 16v forum, just not many! Have a look at Turbominis for info as well, if you havent already. There might be some on TMF but I'm not on there that often.

[Nathan1293]

Cheers Rich.

I know these builds were more popular ~10 years ago. So I'm a bit behind.

I've joined the 16v mini forum, but they are more into engine transplants. I've not joined the Turbo mini forum, mainly because I don't intend to turbo charge the engine. But its still useful info.

Seems there isn't a natural home for these conversions.

The aim I want for the bitsa car is for it to look reasonable standard for a MK1 mini (it will have arches and wide wheels, 10" of course), and the interior to look normal, to something like Tom's MK1 look-alike racer project.

But go like mad

That's what I enjoyed most about the previous hot mini I ran! It was so much fun surprising people.

Nathan

[steve65]

There was a BMW headed Mk1 at Blyton, i think it was something to do with the miniworks.co.uk gang, may be worth asking them?
Steve.

[Spider]

There is a fair bit of welding (Cast Iron and Aluminum) as well as machining work that needs to be done. If you have access to a workshop with these kind of facilities as well as the skill to carry out said operations, you can save yourself considerable time and money.

I looked at these a little while back and another Bike Head conversion. They both can produce 'the goods' but IMO both have some far less than ideal compromises too, mainly for longevity. Also, if you don't have the facilities to do much of the welding and machine work yourself, then at the end of the day, there wouldn't be much in terms of cost between these and a KAD conversion, which is specifically designed for the A Series Engines.

[simon]

I have 90% of the bits to build a turbo 16v for my mk1, I am not rushing it as I want it to look right in there.

I think I have pulled it off right at the min with the turbo 5 port that's in there at the min.

John K at SC is a good start, as I got chatting to him about what I was looking for, then went from there.

There is a lot of info on turbominis if you dig about on there.

Simon.

[Nathan1293]

My old man almost has all the machines we need. He's almost finished building a 1/4 scale traction engine, as well as maintaining the local steam clubs foundation steam roller.

Will have to pay for inline boring the steel crankshaft caps.

But all surfacing and other boring can be done in his workshop.

Also know a good welder for the head. So all in should be relatively cheap.

What are the known reliability issues?

We are gong to create the whole kit, and not purchase any conversion kits.

I do have the SC build book.

[Richspec]

well with all the tools and the build guide there's nowt much to stop you, look at mattg's build diary on the 16vforum , him and his dad have done it themselves as opposed to buying the bits.
Its quite easy to bolt together (i've got one 90% built) the only thing stopping mine is the need for some new camshaft pulley adaptors as they are damaged.
As for reliability i've not heard any bad things? not unless of course you go chasing huge power figures with a turbo or supercharger. One of my mates did all the machining etc himself and its been running for several years with a large turbo on it, obviously the weak points seem to be the transmission but we're talking power levels of around 250hp and more for brief periods

[Spider]

What are the known reliability issues?

Not sure that I'd classify these as 'Reliability' issues but certainly one of on-going maintenance, though depending on how the build is done, can lead to reliability issues without question.

The Cams were originally Chain Driven and so the Sprocket Sizes on the Head can be reduced to bring the Cams closer together and keep the Head (for what they are) reasonably compact.

When they are fitted up on an A Series Engine, it's the norm to Belt Drive the Cams. This brings about a couple of issues.

As the Cams are close together, that limits the size of the toothed pulleys fitted, which in tun limits (very much so!) the size of the Pulley fitted to the Nose of the Crank. All the ones I've seen run a custom pulley and the belt runs through a diameter considerably smaller than recommend by the tooth belt manufacturers, so be life is very short.

For this reason, it is a very wise idea to cut valve relief pockets in the Pistons, so if a belt does let go, it won't mean a total engine rebuild.

The front end of the heads (in the case of the BMW Heads) are cut off where the cavity was for the chain drive and then a plate is usually welded on to seal them up and also forms a bearing support for the Cam Pulleys, so the end up caner-levered a fair way off the head, which will lead to Oil Leaks (well, all the ones I've seen have).

The Combustion Chamber in these heads is very small so a method of de-compressing them is needed, usually a de-compression plate is fitted, while they can work OK, are not ideal and can be prone to leakage.

The original Camshaft in the end does little more than spin the Oil Pump and the Dissy. One of the more refined conversion I have seen (not a BMW one) had the Oil Pump and Dissy driven off the Cams in the Head and so the Original Cam was subsequently not fitted, obviously the Oilways needed to e plugged.

The BMW Engine runs in the opposite direction to the A Series, which means the Cam Timing dictates that the Firing Order is no longer 1-3-4-2 but ends up 1-2-4-3. This sets up really bad harmonics in the Crank, so to help extend it's life you need to run a really good and properly tuned Harmonic Damper.

There's a few more issues, but these are what spring to mind, as I remember others, I'll come back.

Obviously they are done and work, but for the work needed and the cash involved (even doing them in house), I think there are better ways to go.

Having said all that, I do have a T/C 16 Valve 1100 to do, but it's not for me.

[bill773mini]

I've seen two great conversions (not sure if I can link to these here, as I don't know this forum etiquette), one by Sprocket/K1275RS (was based in Warrington I think) on some forums where he offset bored the cylinders then relined to get equal cylinder spacing. Which looks like a great idea for many reasons, not just aligning the cylinders but also reducing crankshaft whipping.

I know Sprocket, he's a mate of Carls who had the K headed Van at Blyton. Sprocket is an amazing engineer with some very clever ideas that work a treat.

As for the conversion it's self it's a brilliant conversion and one I can't recommend enough.

1380 K1200 RS, done 10k miles with little trouble including a 4000 mile drive on the Italian Job in 2009.

[Nathan1293]

Hi Bill

Thanks for the feedback. Glad to hear that you recommend the conversion.

If I sent you my email address would you be kind enough to get in touch with Sprocket and pass on my details.

I was already interested in this conversion. But after I saw his threads about some of the work he has done, I thought that's what I want to do!


regarding the engine firing order, I take it no one has made a custom camshaft to revert the firing order to normal?

I was intending to run the KAD hydraulic crankshaft pulley.

I know Sprocket initially ran with Fiesta camshaft pulleys which may of helped. I know he later changed to vernier pulleys, and seemed to suggest 34T pulleys worked best, I'm not sure what size drive pulley he ran but obviously it must be the relevant ratio for the camshaft pulleys.


Thanks for all comments, very useful so far.

[bill773mini]

Sent you a PM

[Nathan1293]

Thanks for the help Bill.

I've sent a PM and email.

[Nathan1293]

Hi Spider

Thanks for the input.

Regarding the firing order:

"The BMW Engine runs in the opposite direction to the A Series, which means the Cam Timing dictates that the Firing Order is no longer 1-3-4-2 but ends up 1-2-4-3. This sets up really bad harmonics in the Crank, so to help extend it's life you need to run a really good and properly tuned Harmonic Damper."

Couldn't you just make a custom camshaft to return the firing order back to 1-3-4-2 as per a normal 4 cylinder engine?

I know this wouldn't be a "cheap" option.

I assume no-one currently offers this as an option?

Nathan

[Spider]

Couldn't you just make a custom camshaft to return the firing order back to 1-3-4-2 as per a normal 4 cylinder engine?

I know this wouldn't be a "cheap" option.

I assume no-one currently offers this as an option?

Nathan

Yeap, certainly could and it would be a good move I feel.

The bigger part of the cost would be in obtaining or having made Blanks from which they could be ground. They could be CNC Profiled, but they really do need to be Ground finished.

Never know, if you went down that path, there could be a small market for them.

Could be worth having a chat to a CNC shop. Pretty sure the same blank would suit Inlets and Exhausts.

[Nathan1293]

Hi spider

I be been looking into the camshaft idea and I am definitely going to look into convention firing order.

But the harmonic problem you mentioned I think is probably derived from the ca shafts themselves and their relative timing to each other and the crankshaft.

The reason I think this is that the ford Kent engine used to fire in the 1-2-4-3 order. All the recent ohv ford engines fire in the congenital 1-3-4-2 order.

The conventional firing order still fires cylinders 4 and 3 after each other which is similar to the ford firing order firing 1-2 after each other.

But if I make new camshafts in the conventional firing order the relative valve timing will be correct, which I think will make the valve timing much easier. By all accounts setting the valve timing on the BMW cams is tricky, and I think is likely the cause of the harmonic issues.