Although I've swapped a few timing gears "in the frame", the process isn't easy, and unless you're pretty experienced at it, there can be some pretty serious difficulties. One in particular is the possibility of dislodging the plug at the back of the block behind the cam while driving the new gear onto the cam and creating a massive oil leak. It's also necessary to do a detailed check for bent valves before trying to swap the gears, because it's possible for one or more pistons to contact the intake valves after the gear strips and the cam quits turning. Doing a cylinder leak check would be my first project to see if the head has to come off for valve repair. Start by removing the rocker arms, or at least loosening all the valve adjusters so the valves stay closed, then put air pressure into the cylinders and listen for leaks at the carburetor. The exhaust valves are in a position where the pistons can't hit them, so don't worry about them- - - -just be sure all the valves are closed. At some point, swapping engines begins to look pretty appealing, so you can get the disabled one on a stand and do the job right.
Two cams are possible for an upgrade if you choose, the Elgin E-293S, or the Melling CCS-1. The Melling has a little more radical timing and lift than the Elgin, which is pretty much a clone of the cam that was used in the 261 truck engine and the 54-55 6 cylinder Corvette. For another source for the timing gear set, try contacting Nashville Engine Parts Warehouse. (1-800-345-1044) Talk to Jackie, and tell him Jerry who used to teach auto mechanics at McGavock High School recommended him. I've been buying parts from him for over 40 years. He's good at his business! He even found a head gasket set for a 503 GMC engine a while back- - - -in Canada! Keep in touch!
Jerry
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