4.5 '117' engine build

[Tomguy]

Yes to timing chain, yes to timing chain tensioner rail. If the timing chain guide rails are plastic, yes; if they're aluminum-backed rubber, no. You may want to check the valve guides, and replace as needed. You should do the valve stem seals "While it's out"

[vandor]

OK, I did a leakdown test on the right side cylinders of the spare engine (the one form a '76 450SL), and they all had ~70% leakdown - ouch. 0% means there is a perfect seal, a used engine usually will have ~10 leakdown. 70% is really bad. I don't know that if I started the engine if the rings would re-seat. I kind of doubt it.

Interestingly I noticed that the engine had new camgears and timing chain.

So now I am considering using just the heads, or maybe just the left side head on the original '72 280SEL engine.
I looked at the injector holes, and they are different. Likely they can be made to work with the right size injector seal. Does anybody know for sure what is needed?
Alternatively, I think a friend has a set of mid 80s 380 heads. Would those work?
Thanks,

Csaba

[Tony H]

The 380 head will not fit as aluminum engine heads don't fit on iron block engines. I think mixing heads could be probematic. I see 4.5 heads frequently on Ebay, etc. I think your repair would be much simpler if you can find the correct head.

[vandor]

Well, I not only need a 4.5 head, but a D-jet 4.5 head, which *I think* only came in the 108/109s. There is a 1972 SL engine for sale and it's hard to tell, but I think it's K-jet.
But you are right, it might be a lot easier to just find a head. Actually the piece that broke is pretty small, my machine shop could possibly weld it back... that part just goes around the timing chain, it's not 'structural'. I wonder if they can weld it without warping the head...

Csaba
72 280SEL 4.5

[Tony H]

Welding might be an option. heads are welded to reshape combustion chambers and ports all the time. If you want to go that route I guess it's time to tear down the damaged engine to inspect for other damage. The '72 SL should be a D-jet-you can tell right away from the intake manifold.