So, my w123 has an external oil leak, at the rear of the head, under the runner for the #5 cylinder. From what I understand there is pressurized oil galley in that corner. The leak isn’t horrendous, but it has progressively gotten worse over the years. I’d estimate it loses a quart or two over 4K mi. I don’t have to add oil or check it periodically.

Reason I bring this up — the exhaust mani has recently developed a leak, pretty sure it’s the intake/exh gasket. Obviously, replacing that is 7/10 of the work to replace the HG. Thoughts?

Option 1, run it as is, leaking exhaust and a lil oil — Free

Option 2, replace the intake/exh gasket and motor on til the HG really blows — $40 in fluid and gaskets

Option 3, replace the intake/exh and HG. Pay once, disassemble once. —— Around 900 in machine work, gaskets, fluids


Bear in mind, I got a spare complete motor, so catastrophic power train damage isn’t a worry

Which of the two engines are better? I've taken engines that were running fine but had lots of oil leaks down to the long block and installed new gaskets per the thread "Leak free 617" and had good results. I don't like leaks especially because some relatives have a fancy schmancy driveway and would be pissed if I leaked all over it.

Finding a competent machine shop to fix the head is difficult in this area. I'd be tempted to clean up the spare engine with new gaskets and do the easy things like replacing valve body springs on the trans valve body while engine and trans are out.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Having successfully accomplished a head gasket+cylinder head replacement on a 617.952 engine, I'll offer two observations but pass on offering recommendations.

1. Should the head crack or already be cracked, a person is out hundreds of dollars if they care about a core - I don't know what the current core is but for the aforementioned engine, US $600 easy.
2. Based on my experience, I consider replacement of the intake-exhaust gasket to be a pleasure, a universe of labor and challenge away from that which is required to successfully perform a head gasket replacement.

Did the car ever overheat? If not, there could be a chance that you don't have to do any machining of the head.

I agree with 5cylinder on the relative ease of changing the intake and exhaust gasket compared to the head gasket.

If it turns out you have to do some machining on the head, and depending on the condition of both of your engines, maybe you could swap the heads? Easier than swapping the engines, but if the current engine is worst overall than the spare one this wouldn't make sense.

I haven't done either job, but I have heard from a number of people that the heads do tend to crack without overheating just from heat, vibration, and age.

Dkr.

Currently motor was a factory replacement long block. Never overheated, lower end is in good shape. Probably less than 200k on it.

Spare motor has 170k mi when it was crashed. Oil cooler exploded on impact, motor ran for a minute or two afterward. Probably is just fine. There’s a 88 cast into the block under the #5 runner. Maybe it was a factory replacement long block too?

If I was to do the HG job, I’d get the spare head rebuilt, then plop it on my current block, that way I have less down time.

What makes doing the HG job so difficult? My plan was to simply loosen the T chain, remove the cam with sprocket, then pull the head.

As for cracked heads, yes it’s very possible, but I’d be bringing the spare head to the shop first, so if it’s cracked I’m basically out nothing

I disagree that doing the manifold gaskets is 70% of the work of the head gasket. I'd say its more like 20%. Is it a turbo or na? The turbo motors are a lot more work to do these gaskets than the na.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

It would have been nice if it was this simple on my 617.952.

There has been a great deal written about this subject that is available in the archives here. You might consider doing a search and studying to either familiarize yourself with the work or refresh your memory.

Indeed.

More wisdom.