Topic: Engines coming out. What’s a good power upgrade

[thegreg92]

Hey guys, long time no see! I haven’t driven my 79 450SEL in several months and noticed a large pool of oil underneath. I’ve decided to pull the engine to replace the rear main seal, oil pan gasket and possibly the timing cover to clean up the oil leaks.

I’m considering doing some power upgrades as it barely passed emissions last month and it would be a good time to do it with the motor out. I’m also going to do a front end rebuild.

It’s a USA M117 4.5 and I’m considering Euro pistons to increase the compression ratio. Has anyone had success with this? Any other good ideas? I’m a seasoned Mercedes tech and not afraid to try anything reasonable.

Thanks!

Greg

[secondslc]

Any later generation M117 from a 560 car perhaps? I would imagine one can get a newer style CIS working.

Or heck, the M119 in its first few years was CIS

[TJ 450]

You could rebuild this M117 and have some custom forged pistons made and increase the compression ratio to 10:1. I’d also have some custom cams made. The K-jet should be more than capable of dealing with the required enrichment.

Just an idea.

Tim

[3l33ter]

The exhaust manifolds are a big restriction on these engines.

[Stu]

I've rebuilt a few M117's with Euro 8.8:1 pistons and the change is quite noticeable. Most of the Euro motor HP comes from the compression ratio. I've also rebuilt one early 117 with pistons I had made at 10.5:1. The problem with building an engine with American made cast/machined aluminum pistons is that you have to leave about .002-.003" piston to wall and they get a bit noisy. The clearance is required since there is no expansion control in hot rod pistons. The factory pistons, as you know, have cast in steel bands to control piston expansion and as such allow much tighter piston to wall clearance. We found the big difference was from 8:1 up to 8.8:1 and while going higher was better, the overall engine was less satisfactory.

Stu

[rumb]

Stu,  Hi,  I bought the 6.3 old race car from you a couple of years ago. 

[PMcG]

I found this tidbit regarding the M117 engine on Classic Jalopy https://www.classicjalopy.com/2019/02/the-m117-968-560-engine/ :

"One particularly restrictive element of the US and Japanese M117 is the exhaust system.   There is a crossover pipe that joins the output of both banks of cylinders into a single catalyst.  Upgrading this part of the exhaust system is the simplest way of gaining more power of this motor." 

Has anyone tried this?  And if it's worth doing, has anyone done it?

[rumb]

Crossover pipe are a proven method of improving exhaust gas flow.

[thegreg92]

Well I got the engine out and began tear down. The rear main seal cut a nasty groove into the crank. I’m considering putting a sleeve on it. Has anyone had any luck with this type of product? Rockauto has one made by National.

Also, does anyone have a good source for the idler, distributor, and crank sprockets other than the dealer? I’ve seen aftermarket parts available here and there but out of stock of course.

Thanks guys!