Welding K1100 Cylinder Head

[Melvyn Best]

Would it be possible to make a short stroke engine using an Austin 1300 crank (that had larger big ends ) offset ground and Cooper S rods ( which had smaller big ends ? There used to be engines conversions that were nearly 1500cc where the crank was offset ground to make a long stroke engine .

 

[minimutly]

Yes sure, same principle. 81.3 becomes 84 point something (can't remember exactly). So 3mm shorter or thereabouts should be ok. Stronger than a long stroke too.

Bore spacings are very very similar for the 1275 engine. From what I remember the valves aren’t totally aligned with pistons when fitted, although this can be improved by offsetting if reboring for bigger pistons.

People have fitted the 8v to 998 engines to good effect but I think a pocket has to be machined away from the top of the block/piston wall to make a space for some of the valves.
So in my book it doesn’t fit the smaller block, as you must get quite considerable valve shrouding because of that. Mind you, you don’t need as much flow for a smaller engine. In any case it just doesn’t seem okay to me.

In my head the paired bore spacing on a 998 engine would lend itself to shortening a bike head with a central cam chain like a 90’s Yamaha. The 600 head doesn’t have the footprint and I’ve never been in the room with a fz750 or fzr1000, to be fair by now if it was a goer someone would have done it by now.

@minimutly ’s 1000 engine would be a 1275 block decked to take a short stroke crank like a 970 cooper engine. Or extra long Conrods for crazy revs.

Working on the extra long conrods, but struggling to get a piston/rod combo that minimises machining of the block, I don't want the piston down the bore, obviously can't have it come out the top (too much)

 

[Popcorn]

Bore spacings are very very similar for the 1275 engine. From what I remember the valves aren’t totally aligned with pistons when fitted, although this can be improved by offsetting if reboring for bigger pistons.

People have fitted the 8v to 998 engines to good effect but I think a pocket has to be machined away from the top of the block/piston wall to make a space for some of the valves.
So in my book it doesn’t fit the smaller block, as you must get quite considerable valve shrouding because of that. Mind you, you don’t need as much flow for a smaller engine. In any case it just doesn’t seem okay to me.

In my head the paired bore spacing on a 998 engine would lend itself to shortening a bike head with a central cam chain like a 90’s Yamaha. The 600 head doesn’t have the footprint and I’ve never been in the room with a fz750 or fzr1000, to be fair by now if it was a goer someone would have done it by now.

@minimutly ’s 1000 engine would be a 1275 block decked to take a short stroke crank like a 970 cooper engine. Or extra long Conrods for crazy revs.

It's been done with a CBR600F1 head, seen a video of that one. Even more work than the BMW head though.
Someone claimed it's had been done with a R1 head but he also said the R1 had 5 Valves per cylinder. So think he was getting confused with a FZR1000.....Not seen any evidence of it though.

 

[aesmith]

Just thinking back to the "dry decking", don't you have to block off the passages in the cylinder block as well? Otherwise if the gasket fails your coolant and oils is going everywhere anyway.

 

[Popcorn]

Yep you do see post 16

You weld a pipe onto the side of the head and bolt another onto the block using one of the core plugs. The oil feed is taken from the oil pressure pipe feed on the front of the block, you need to remove a Allen screw from the head and drill and tap it for the 1/8 NPT fitting.
The bloke who first di this conversion has website covering that first one it's here:
http://www.lojomo.com

 

[minimutly]

Yep you do see post 16

On the 8vK100 (and maybe the K1100?) the oil feed comes up through the head deck close enough that a bit of welding and drilling allows you to use as intended. For some reason they machined half the casting away on the K1200, so you have to go down the external pipe route.

 

[Popcorn]

It's just easier to dry deck it and run and external oil feed, just like with a Turbo.
It also has the added bonus of making the cooling system fully flowing and far more efficient......

 

[minimutly]

It's just easier to dry deck it and run and external oil feed, just like with a Turbo.
It also has the added bonus of making the cooling system fully flowing and far more efficient......

Conflating two different things there - is conflating the word? Never mind. Dry decking is for the water jacket, big yes for that, faffing about with oil feed pipes when you don't need to is silly, there is enough clutter under the bonnet already.
If the K1200 had the meat in the casting I would use the mini oil way up to the head, no question. Since it's not, and I plan to have a turbo feed pipe anyway, I will go with a poxy pipe to the head.

 

[Popcorn]

Dry decking means just that NO fluids pass between the deck of the head and block......

 

[minimutly]

Dry decking means just that NO fluids pass between the deck of the head and block......

Obviously not for everyone it doesn't - ask Swiftune, MED, or any of the Mini miglia boys.

 

[aesmith]

Yep you do see post 16

Cheers. I can't see where that said anything about welding up the holes in the block as well as the head.

 

[Popcorn]

Obviously not for everyone it doesn't - ask Swiftune, MED, or any of the Mini miglia boys.

I don't need to ask anyone, as always with mini's been a oddity in so many area's. Terms used by mini people/companies are just incorrect........

 

[Popcorn]

Cheers. I can't see where that said anything about welding up the holes in the block as well as the head.

Did you not check out the link to Greggs website, it explains it all there........

 

[minimutly]

I don't need to ask anyone, as always with mini's been a oddity in so many area's. Terms used by mini people/companies are just incorrect........

Incorrect or not, as applied it refers to the water passages only, But I take your point.
Anyway, I made the head end aluminium nipple, but have held off welding it on until I have the u hose. No-one seems to be selling these on their own. Hose ordered is 32mm. Also ordered some aluminium to make the inlet manifold, more today.

 

[Popcorn]

See this has always been the problem, people don't understand it use what is basically 'slang' terms, all encompassing if you will.
But that doesn't make it correct............

 

[minimutly]

My new "u" bend pipe came today, fits the one stub I made fine, but I do think I could have gone down a size, especially after inspecting the water outlet port in the head - it's tiny.
I don't much like the oil drain pipe from the bottom of the cam seal plate, it's just making a "noisy" area more crammed. So I'm toying with moving it to the back, to the lower end of the return in the casting - I'll have to make an insert, bore out and tig it in, the other thing to do is move the sealing end insert strip up, this will reduce any tendency for oil to leak here.

 

[Popcorn]

MadMatts Conversion Kits take the oil drain from the back of the head rather than cam plate. More or less straight down the the fuel pump/oil return.
If I'd seen it before I finished my Mods I'd have gone that way, much neater design.

 

[minimutly]

MadMatts Conversion Kits take the oil drain from the back of the head rather than cam plate. More or less straight down the the fuel pump/oil return.
If I'd seen it before I finished my Mods I'd have gone that way, much neater design.

Not come across madmatt, I'll do a search

 

[Popcorn]

He's used to occasionally frequent Turbominis not so much now, he's in Australia and can be found on ausmini.com

 

[sasquar]

madmatt is one of the og's. Matt Read is his actual name (think the spelling is right) he's been around minis all his life and has forgotten more than most, he was doing these conversions when most of us had never heard of a 'bmw k100'..... hes also done some other daft conversions, like fwd v8 mini as well.... runs a company called readspeed, which i believe his father started back in the day...... he's still about on instagram and fb i think, i see stuff from him ocassionally, and there pretty much all i use (other than here/pistonheads and a couple of others.... havent been on tm for donkeys years, might go see if my login still works....)