BMW Heads, porting, cams, suitability for big bores.
Posted: Thu Dec 18, 2014 6:03 pm
ASBO was bought an 86mm forged crank the other day. The resulting financial shock made me put the old crank, rods and shortly other bits on ebay.
This new crank has made me question the whole parameters of my engine. It appears the existing pistons have had a gnats fanny skimmed off them and I don't really like the idea of whipping another 2mm off. I'd say that I'm probably going to get a set of H Beam rods and proper short 73.5mm pistons.
This brings attention to the head and the carb. A while ago, I decided I didn't want to hack the dash about for the weber box, but go the IDA route instead. I am now forced to look at the compression ratio of the head and it's going to be pushing it. I wondered whether it would be an idea to rip out the cam, head, carb, manifold, dizzy and sell them all as one thing and then BMW head it. The simple reason being that it would kill lots of birds with one stone. No hole in the bulkhead, no hole in the bonnet, sensible fueling and ignition, etc.
I think my old stuff would command quite strong money and if I'm spending a fortune on the bottom end, I might as well go the whole hog.
Quite clearly, a BMW K1100 head is designed for a 1100cc engine. This is not a 1460. I am aware that RS cams take things out a bit, but it may be an idea to take the ports out a bit.
This is a project which has been in the shed for years. It's been gradually creeping forward and something I have been amassing a pile of parts for over the years. It's not really urgent enough to go phoning anyone, but would merit a discussion, or any useful pointers.
The mini is relatively low priority and I'd buy a Sylva Striker over a KAD head. I'm a bit of a tinkerer and like to do my own work, where possible.
Stu
This new crank has made me question the whole parameters of my engine. It appears the existing pistons have had a gnats fanny skimmed off them and I don't really like the idea of whipping another 2mm off. I'd say that I'm probably going to get a set of H Beam rods and proper short 73.5mm pistons.
This brings attention to the head and the carb. A while ago, I decided I didn't want to hack the dash about for the weber box, but go the IDA route instead. I am now forced to look at the compression ratio of the head and it's going to be pushing it. I wondered whether it would be an idea to rip out the cam, head, carb, manifold, dizzy and sell them all as one thing and then BMW head it. The simple reason being that it would kill lots of birds with one stone. No hole in the bulkhead, no hole in the bonnet, sensible fueling and ignition, etc.
I think my old stuff would command quite strong money and if I'm spending a fortune on the bottom end, I might as well go the whole hog.
Quite clearly, a BMW K1100 head is designed for a 1100cc engine. This is not a 1460. I am aware that RS cams take things out a bit, but it may be an idea to take the ports out a bit.
This is a project which has been in the shed for years. It's been gradually creeping forward and something I have been amassing a pile of parts for over the years. It's not really urgent enough to go phoning anyone, but would merit a discussion, or any useful pointers.
The mini is relatively low priority and I'd buy a Sylva Striker over a KAD head. I'm a bit of a tinkerer and like to do my own work, where possible.
Stu