By Don Nester
Chapman Report – May 1979

Several articles ago, I described my episode in the rebuilding of my Europa TC engine. Although my description provided some insight into the rebuilding process, I did not provide any insight into those things that could be done to improve the engine life of the Twin Cam. One of these modifications is in respect to the valve guides.

When rebuilding a Twin Cam head, the original steel valve guides should be replaced with bronze valve guides. The reasons for doing this are: 1) To decrease clearance and; 2) To improve the bearing surface for the valve stem. Decreasing the clearance requires the use of bronze valve guides. This decreases the amount of oil that is sucked into the combustion chamber and therefore, reduces the amount of oil that the Twin Cam burns.

The improvement of the bearing surface for the valve stem will reduce the tendency to wear out the valve stem. The original steel guides do not wear out, but will cause the valve stems to wear out in 35,000 miles which results in heavy oil burning. The bronze guides will extend valve stem life and therefore, decrease the tendency of the TC oil burning.