Top of end of one engine with bottom end of another?

[Chronohunter45]

Hey all. I'm currently attempting to restore my GS to its former glory after a crank are bearing blew up. The entire top end of my engine is perfect condition, valves and all are clean and in excellent condition. I have in my possession another engine, runs, works great, but there are two broken bolts at the exhaust ports which must be drilled out (which I would rather not do...). They cannot be vise-gripped off either -- too short.

My question is, can I combine the bottom of the good engine (crankcase, cylinder portion of top end) with my old top end (valve portion of top end, and head cover and cams) without issue?

Reply back soon please.

[jestercinti]

YES...but some models have differences.

One that I can think of is the tachometer gear in the head...newer models have an electronic tachometers.

There are other little nuances, but that's the main one I can think of.  The electronic tach is 2004+ in the USA.

[Chronohunter45]

Both engines are pre 2004. I guess it'll work then.

[Zethioth]

From what I've read, you should make year the engine pieces from both engines were manufactured as far close to each other as possible.

If I remember, the heads were mated very specifically to the bottom ends for the years.

[dgyver]

From what I've read, you should make year the engine pieces from both engines were manufactured as far close to each other as possible.

If I remember, the heads were mated very specifically to the bottom ends for the years.

I have never heard this before.

Most of the engines I built have been of parts from various years (most unknown). 
Even then any head will work on any bottom end. There are a few minor issues to deal with 04+ & pre-04.

[adidasguy]

Cam journal caps are mated to the head and machined together.

The rest of the engine can be a total frankenstein.

Through '02 heads had a mechanical tack. 04+ does not have a place for the mechanical tack and an oil cooler was added to the bottom.

Still, bottom, middle, top: mix and match to your liking.

[Bluesmudge]

Yup. My bottom end is '06 with 28,000 miles. Top end is an '05 with 20,000 miles. Mix it up!