"New" 79-300CD with blowby

[dazsa]

I just bought a 1979 300cd for $500. The body is rust free and the interior is in very good shape, new battery and starter.

It starts right up but it idles very poorly; however, it drives well once moving.
It does have significant blowby (1 quart+) per tank of fuel.

The fuel filter is dirty.

So, I may have to replace the engine, but I want to try other things first.

I will replace the fuel filters, adjust the valves, and clean everything I can clean.

What else can I try before I resort to another motor?

Thanks, as always!

Don