117.983 vs. 117.986

I've got a '73 450SEL with a smokin' engine...
The opportunity to obtain a CIS 4.5 has arisen, but
I'm wondering if the blocks are compatible.
Any help would be appreciated.

[cth350]

I think not. But you have to check the head gasket part numbers to be sure. You'll have to swap the whole fuel injection system. unless you can reuse the heads from the EFI car.

I have a 117.983 motor on Long Island, NY (presuming you're with a few hundres miles); if you're interested.

-CTH

Well, unfortuately I'm more than a few hundred miles
away (So. Cal)...
My hope was to have a rebuild nice and ready for when
the time comes (as it seems to be nearing), I had
figured on swapping over the EFI anyway, based on
hearing it is a better system than the CIS. If the
heads aren't compatible that would put a little kink
in things, but I could have them done while the beast
is down.

[stevebfl]

Your problem is probably only valve guides/seals. A good valve job is all you probbly need. Getting a used motor will only get you another one that needs valve guides/seals. They are all old!

The lower ends of those motors go forever.