Howdy Joe,

The official verdict is that the cam has worn out to the point where it no longer has enough vacuum to start properly.

That would be a terribly worn cam indeed. Have you measured the lift, or lack thereof? Is the engine otherwise healthy? Cranking compression? In other words, is the cam the only known problem? The cam and lifters can be replaced, rings and inserts installed, and freshen the head. That can be done for about $200 in machine work, about $400-$600 in parts, and a lot of your time and effort. Of course if the engine is badly worn it will be more work and money.

Regardless, your question is about replacement engine alternatives. The easiest and least expensive route is to buy a rebuilt or used B20. They come up from time to time, sometimes cheaper than rebuilding your engine. Check the classifieds here, IPD, Volvospeed, and Turbobricks. Also check craigslist as they do come there every now and then too.

Changing to a B21/23/230 is certainly an option but is not easy nor would it be inexpensive. Some custom bracketry/adapters and a decision about upright or slanted will determine the course of that choice.

Choose a diesel carefully. A diesel project is not to be taken lightly. If you know what you are doing or you are willing to pay some people who do know what they are doing, it can be done. It won't be inexpensive.
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Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man.