BMW 2-valve Boxer cylinder heads overhaul
The processing of the cylinder heads begins in an industrial washing machine, in which they are cleaned of oil, soot and dirt with special cleaning agents. The surfaces are then blasted in a pressure blasting unit with ceramic balls.
Blasting with ceramic balls produces a velvety surface that looks very classy and is easy to clean. With this process, the surface is compacted and there are no open pores as with glass blasting.
First, the old valve guides are pressed out. The basic bores for the new oversize valve guides are newly set and then honed to their final dimensions. The new oversize valve guides with valve stem seals are then shrunk in using liquid nitrogen (-196° Celsius) (heads are heated to 230°).
In the next step, the old valve seat rings are removed. Here, too, the basic bores must be milled to the exact shrinkage dimension (tolerance +/-0.01mm) of the new oversize valve seat rings (suitable for lead-free).
When all the basic bores are in place, the heads are heated again to 230° Celsius. The seat rings take a bath in liquid nitrogen (-196° Celsius) and are inserted exactly into the basic bores with a guide mandrel.
In the next step, the valve guides are honed to the final dimension of the corresponding valve stem diameters. Honing produces a very smooth and low-friction surface compared to reaming with reamers.
Then the seat rings are milled on our Serdi valve seat machining with special contour steels. Most of the seat ring contours we use are our own developments. We have been machining cylinder heads for almost 30 years now and have the right contour for practically every application. For control purposes, the valves are checked for tightness using a vacuum tester.
The last machining step is the face milling of the cylinder head and the valve cover face. A horizontal grinding and milling machine is used, which has been designed exclusively for this purpose and which mills the surfaces 100% flat.
Finally, the cylinder heads are completed with new valves, new valve springs and new valve wedges ready for installation.
-Dismantle, clean and check the heads
-blast cylinder heads with ceramic balls
-Remove valve guides and exhaust seat rings
-make base holes for valve seats and guide
-Renew/shrink valve guides
-Renew/shrink in exhaust valve seat rings
-Hone valve guide to final size
-Mill valve seats on SERDI 100
-Check valve sealing with vacuum tester
-Mill cylinder heads flat on both sides (cylinder and valve cover side)
-Assemble valves, spring plates and valve springs
-Price applies per cylinder head
-Parts package included in price
Parts list (included in price):
1 exhaust valve seat
2 valve guides
2 valves 8mm stem
4 valve wedges
2 valve springs
