I am going to do a head gasket on my 617 n/a in the near future. I have a junk 616 that I was thinking of tearing down for practice and to get more familiar with the internals. Aside from one being a 4 cylinder and one being a 5 cylinder, are they similar enough for it to be worth my time as a learning tool? The 617 is from my 1981 300D, I don't know about the 616 as I got it free already pulled out.

Should be very similar so techniques would cross over from one to the other.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

If the 616 is possibly a good engine I would not tear it apart. Any history with it? As for learning the head gasket change on the five cylinder. It is not that tramatic. Just following instructions with a little assistance should get you there.
Otherwise the two engines for your purpose are identical basically. They just hacksawed the last cylinder off the 617 so we could complain about the lack of power forever.

The 616 was a running engine when pulled, but sat outside exposed for several years. I pulled the oil cap off, and I can see a good amount of rust on the camshaft, so I'm assuming the engine is essentially shot. I didn't figure that the head gasket job would be too traumatic, I just wanted to get a good hands and eyes on feel for the insides of one of these engines, before I tear into my running engine.

But if it was me I would not bogart the 616 engine, they're probly gonna become scarce in good used running condition in a few years. You will probly need a hoist to pull the 617 iron head, heavy bastard. Whats the circumstances of the 617 engine, mileage, symptoms, etc? Have heard they deserve valve work at/near 280/300k miles..... secret of longevity to get 500k outa the block.

(edit: otherwise salvagable parts from the 616 oughta include manifolds if they're pre-1980 uncluttered with EGR valve.... probly worth a bottle of bourbon at least.

The 616 isn't in running condition anymore. (By the way, its the same one that I puled the alternator bracket off of for you. Good bourbon) At the very least it would need some head work and a new camshaft, and I haven't seen the inside of the bottom end yet. If the internals look good, I'l probably cover it and save it for the Willys CJ 2(40D) project I've been comtemplating. Unknown on the mileage of the 617, the parts car I bought for it had 140K on the nonworking odometer. But it started right up after not having run for at least a year, and it ran really smooth. I was able to drive the car about 40 miles to my house. It has started to idle a little rough, and there is oil in the coolant. Other than that it is great. I figure I'll change the head gasket before I swap it into my 300D, along with valve stem seals and a valve adjustment.