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Old 09-09-2015, 12:39 PM
MaxC107 MaxC107 is offline
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Join Date: Oct 2014
Location: Central Indiana
Posts: 48
M117 and 722 are tired in my SLC. I have a few questions about a rebuild.

The M117 and auto in my 1974 SLC are getting tired and are going to need an overhaul in the next 5,000 miles if I'm nice to it. It's burning oil and I'm getting a bottom end noise when its cold coupled with low oil pressure at temp. I've built a few high strung SBF, SBC, and Pontiacs and done stock rebuilds on M113 and M104 engines so this process is not new to me but there seems to be an aura of fear around the M117 rebuild.

I feel I have 3 options:

1:Factory 450/722 3 speed rebuild. Looking online all the parts seem to be around the same cost as Pontiac stuff and I feel a $1500 budget is reasonable if I assemble it myself, the bores aren't trashed, and have the machine work done by people I'd normally use. Is that in the right ballpark assuming the fuel system is more or less ok how it is? If the pistons are done, which they may be given the bottom end noise, that budget is shot.

2: 560/722.3 combo. Will it bolt up? I could pick up a 560/722.3 next time a 560 W126 ends up in a junkyard in this part of the country and spend next summer piecing that together and drop it in over the winter. I understand I would have to convert to K jet but that's all available and an upgrade from the D-Jet anyway. I would prefer to do a factory 560 rebuild and swap rather than a 450 3 speed rebuild. I figure the same $1500 for a rebuild plus another $300 for the powertain at a U-pull yard and $500 for various swap parts totaling $2300.

3: American swap. I have a bad Pontiac fetish and I would consider a 455 if Mercedes stuff is astronomically expensive ($3000+). I figure that would cost about $2000 based on experience.
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