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Performance Notes, Inspiration Leads To Innovation For Resurfacing Tool
By Jerry McLain
All too often we start with a good rebuildable engine core only to find the camshaft thrust surface has taken a beating at some time in its previous life.
This is not a new problem for engine builders. Machinists have come up with a number of solutions to these problems throughout the years. Some of those methods of repairing worn thrust surfaces may work for you and your shop, but most require lifting the block in and out of the milling machine and quite a bit of set up time.
We build a simple tool to make repairing the camshaft thrust surfaces easy, and most importantly - profitable (about ten minutes start to finish). Our tool is called a "Camshaft Thrust Resurfacing Tool" and it fits into the camshaft tunnel of the engine block. We feel 99 percent of all automotive machine shops already have valve seat grinding equipment with various stones and pilots; the Camshaft Thrust Resurfacing Tool allows you to use your .375" valve guide pilot,
valve seat stone holder and stones to regrind the worn camshaft thrust surface. The cam bearings must be removed before the Camshaft Thrust Resurfacing Tool can be inserted into the block.
After the tool has been inserted into the block a .375" pilot is inserted into the tool (see Photo 1 and 2).
Photo 1 & 2
You will need a 3-inch general-purpose flat stone to be able to resurface both small and big block engines. Carefully dress the stone flat by setting the diamond at 0°. Now dress the outside diameter of the stone with the stone dresser set at 0°. The large stone will run much more smoothly after both surfaces are dressed (see Photo 3).
Grind the thrust surface for a few seconds and check your work. The thrust area may only need a light touch up to create a desirable, oil retaining, new thrust surface (see Photo 4). If the block is worn badly then more grinding is required and an after market thrust washer will be required between the cam gear and the block (see thrust washer - Photo 7).
The next step we do is to check the fit of the camshaft thrust washer on the engine using a straight edge (see photo 5). The camshaft thrust surface is the same height as the timing cover surface. Place the straight edge across the timing cover surface and grind the thrust surface until the thrust washer just fits between the straight edge and the block (see Photo 4).
Photos 3 through 7
After grinding recheck the surface using the small straight edge placed across the adjacent block surface to determine when enough metal has been removed. Again the thrust washer should just fit under the straight edge (see Photo 4 and 5).
We are careful to keep the camshaft in its original position in the block. That is why we keep checking with the straight edge as we grind. The lobes on a camshaft are tapered slightly. If a camshaft is too deep into a block the lifters will rotate too fast and cause problems. If the cam is not deep enough the lifters will not rotate at all and will scuff and wear quickly (Photo 5).
We have used the Camshaft Thrust Resurfacing Tool on many blocks since we invented the tool. We have noticed that if a block has a great deal of core shift the tool may not enter the camshaft tunnel because the lifter bosses are down in the tunnel. Blocks with that much core shift may not be a good choice for rebuilding and the tool kind of lets you know this.
We have developed this tool for both small block and big block Chevys. The blue anodized tool (see Photo 6) is for the small block engines. The natural aluminum anodized tool is for the big block engines.
Our frustration with existing repair methods led to our inspiration to create this tool for our own use. But we also want to make it available to other shops that suffer the same challenges. It's been extremely helpful to us and will most likely be helpful to you as well.
You certainly have ideas in your own shop that can be turned into tools that others would be interested in as well. Talk to your shop supplies representative to find out how to develop and market such a product. Not only will you be helping an industry, by selling the tools you'll be helping yourself, too.
Jerry & David McLain operate McLain Automotive in Cuba, MO. For more information about the Camshaft Thrust Surface Repair Tool, visit them online at www.mclainsautomotive.com.