What should I check on the engine of a recently purchased 122 ?

John,

Ondrej

Just do not want you to get new carbs thinking that they will solve all of the problems and then find out there are other issues.

If you have access to the equipment for a leak down test that will give you even more specific info on the condition of different parts of your engine, but a compression test is a good start.

You should check the valve lash adjustment.

Also check to see if the tops of the valve stems are at approximately the same height. If they are not it indicates probable wear in the valve seats. The heads were originally designed for leaded fuel, so unless someone has put in hardened exhaust seats, the original exhaust seats are likely to be wearing away, causing the valves to rise higher in the head.  So if there is one or more stems that are taller than the others that indicates abnormal wear.  The only cure is to remove the head and install hardened seats.

Another engine check should be cam lift in order to check to see if there is abnormal cam wear.
You will need a dial indicator with magnetic base to do this, but they are not very expensive at places like Harbor Freight Tools. You should check the amount of lift of each cam lobe. You can check with the pushrods in place with the indicator in the top of the pushrod. It is very common to see significant wear on one or two lobes while the rest are fine.

As to alternatives, the first step is to see where the problems are. If they are only in the head, fix the head. If its the cam, replace the cam and lifters. It's when you get into problems with the piston rings and bearings that a complete rebuild becomes necessary.

The next check that I would make is the distributor. Check the timing at both idle and around 3,000 rpm and note the advance. Also look to see if the timing mark is stead or bouncing around. If it is moving around that is a sign of bushing wear in the distributor. You can also check by taking off the distributor cap and seeing if the rotor will move from side to side. If it does, the bushings are worn out and the timing is going to be off causing all sorts of problems, including overheating.

Regards,
John
Vintage Performance Developments