Cylinder Head U20
Datsun Roadster U20 Cylinder Head Cam Tower Shim - Set of 5 AFTERMARKET USA
U20 CAM TOWER SHIMS
High Quality Aluminum. These Cam Tower Shims are precision machined. Cam Tower Shims are used to make the upper chain tight again when a cylinder head has been overly-planed. It should be noted that most of the time cylinder heads are surfaced on the bottom. However, there are times when they are surfaced on the top. It may be necessary to use our shims in conjunction with one of our thicker head Gaskets to restore accurately the same amount of material to each side of the cylinder head that was removed. Use the guide below to determine how much has been surfaced off the top of your cylinder head.
.025 Order by PART# 1152A
.032 Order by PART# 1152B
.040 Order by PART# 1152B4
.048 sometimes .050 Order by PART# 1152C
.060 Order by PART# 1152D
GUIDE: This is a simple guide to determine what size cam tower shims you need or if you need them at all. When a cylinder head becomes warped the top will warp up in the center like a banana. Most, not all, machine shops will surface the top of the cylinder head to get the head flat again. A good machine shop will always minimum surface the cylinder head to make it flat and not be arbitrary about how much they will remove. After checking and shimming the fixture holding the head, they will pass the cutter over the warped area removing the excess material. In performing this procedure all of head bolt hole recesses, the ones on top of the head NOT the cam towers, in the center area, will be less in depth than the two head bolt recesses at each end of the cylinder head. The depth of the holes are measured from the, top, machined surface of the cylinder head casting to the, bottom, machined surface of the head bolt hole. A little tricky to compute the number at the front of the cylinder head.
Subtracting the depth of the center holes from the following number: .480 will give you how much has been surfaced off the top of the cylinder head in its life time.EXAMPLE: Depth of the inboard holes .440 subtracted from .480 = .040 shims needed. To configure whether you need a thicker head gasket you would use these numbers in relation to the original thickness of a U20 cylinder head which is 4.528 to compute what was surfaced off the bottom. It is possible to have more surfaced off the bottom of the head than the top. Click here, to view the thicker U20 head gasket.
NOTE:Please also look at PART# 2551 to determine if you need thicker lash pads if you are using a re-ground cam or thicker cam tower shims.