Red's Engine Talk
Camshaft End Clearance March/April 2005
We all know to check crankshaft end clearance when we assemble an engine, right? How about camshaft end clearance?
In the first few decades of our flathead V-8's lives, this was seldom a problem. Now that it has been over 50 years since the last flathead was made in the USA, parts may be worn a bit more.
I have never seen a specification for camshaft end clearance, but my guess is that .004" - .008" would be in the ball park.
So what do you do if you have .030"?
One idea would be to eliminate the possibility of the front cover being badly worn.
The early, 1932-1948, cams had timing gears that thrust to the rear, against the block. The late, 1949-1953, cams have timing gears that create thrust forward, against the timing cover. If someone has used an early timing cover with the late timing gears, the cover is probably worn out. The early cam and cover were not designed for front thrust, and there is little oil at the front of the gears.
The late camshafts have an oil passage that takes oil from the front cam journal and feeds it through a passage in the cam to the front of the gears.
If your front cover is in good condition and you still have .030" end clearance, you could eliminate the timing cover gasket. The cover can be sealed to the block with silicone gasket maker. Also, timing cover gaskets vary in thickness from different manufacturers, and perhaps you could use a thinner one.
If you still have too much clearance, you could have the front of the block machined to remove as much as needed. Or, you could find a thrust washer to go between the cam flange and the block to take up some space.
If the wear problem is on the front of the block, insure that the thrust surface is smooth before assembly. That surface could be fly cut if it is damaged. Done correctly, that could make it easier to find a proper thrust washer.
One possible source for thrust washers is rear end differential axle gear thrust washers.
On engines with press on gears, you may be able to press the cam gear on so that it is offset enough to solve the problem.
Thanks to Miles Schofield for this column idea.
There are some new head gaskets available. They have enough time on the them, and engines built with them, that is safe to say that they are working well.
The construction is much like head gaskets made for many new and late model vehicles. They utilize graphite in a form that is very resistant to blowing out or moving due to combustion pressures.
They work well with both aluminum and cast iron heads. There is no requirement to use sealer on these head gaskets -- simply apply them to clean surfaces. They are manufactured by Best Gasket Company and are available through many suppliers.