Page 1 of 1
r100 cylinders
Posted: Tue May 10, 2011 3:06 pm
by lrz
Taking the lazy route here..
I'm curious if standard bore '77 cylinders & pistons can be swapped w/ '78-'79 version. I know the later wristpins had actual circlips vs the spring-wire type, but am unaware if there is/are larger differences to consider.
Thanks.
Re: r100 cylinders
Posted: Wed May 11, 2011 5:03 pm
by lrz
Bueller,Bueller, Ferris Bueller?
Re: r100 cylinders
Posted: Wed May 11, 2011 6:27 pm
by mattcfish
lrz wrote:Taking the lazy route here..
I'm curious if standard bore '77 cylinders & pistons can be swapped w/ '78-'79 version. I know the later wristpins had actual circlips vs the spring-wire type, but am unaware if there is/are larger differences to consider.
Thanks.
Yes. As long as the piston's diameter and bores are within spec. The rings are different if you go from Iron liners to Nikasil.
Re: r100 cylinders
Posted: Wed May 11, 2011 10:12 pm
by vanzen
Swapping cyls. will have one considering iron or Nik, O-ring or gasket.
And the Ø of the hole in the block into which it must fit ...
Often neglected about piston swapping is
squish-band profile of the piston vs head – and the compatibility that is a result ...
Yes, always match the BMW size designations (A,B, or C) when swapping pistons into cylinders
or do the math with a micrometer ...
Choice of rings will be dependent upon the bore material.
Re: r100 cylinders
Posted: Wed May 11, 2011 10:20 pm
by lrz
Vanzen, those are the exact considerations I have. What I may do is install used cylinders (iron)w/ their own pistons . I believe the stroke remains the same for those years.
I'd prefer to retain my current heads; where might I find info regarding "new" pistons (78-79) w/ original heads (77)?
Re: r100 cylinders
Posted: Mon May 16, 2011 2:50 pm
by Rapid Dog
Not to be OT, but I've got '81 Nik cylinders and '78 squishband heads, seems to work fine.
Now I'm thinking of installing non-squish dome 9.5 pistons to raise the compression from the flat top 8.2 pistons I currently have.
I've been told there should be no problem...
Re: r100 cylinders
Posted: Mon May 16, 2011 4:32 pm
by George Ryals
Rapid dog, it sounds like you would end up with a wedge shaped squish area with the wide part of the wedge towards the outside.....trapping mixture.
Chuck the pistons up in your lathe (or your friendly neighborhood machinist's) and cut a flat squish band as wide as the corresponding squish area in the head. You can cut the cylinder base or head surface to regain the little bit of lost compression.