Author Topic: Engines coming out. What’s a good power upgrade  (Read 358 times)

thegreg92

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Engines coming out. What’s a good power upgrade
« on: 12 September 2020, 07:11 PM »
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
1982 W123 240D - sold
1979 W116 450SEL
2007 W164 ML350
2011 W212 E350 Bluetec - lease expired
1978 W116 300SD - sold

secondslc

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Re: Engines coming out. What’s a good power upgrade
« Reply #1 on: 12 September 2020, 07:38 PM »
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
1979 6.9
1983 urQuattro
1991 200 20V Avant
1993 Corrado SLC
1996 SL600
2009 Super V8

TJ 450

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Re: Engines coming out. What’s a good power upgrade
« Reply #2 on: 13 September 2020, 06:36 AM »
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
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

3l33ter

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Re: Engines coming out. What’s a good power upgrade
« Reply #3 on: 15 September 2020, 06:10 PM »
The exhaust manifolds are a big restriction on these engines.
'75 280S
'77 6.9
'82 300TD

Stu

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Re: Engines coming out. What’s a good power upgrade
« Reply #4 on: 27 September 2020, 05:59 PM »
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
Retired MB mechanic/shop owner

rumb

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Re: Engines coming out. What’s a good power upgrade
« Reply #5 on: 28 September 2020, 06:18 AM »
Stu,  Hi,  I bought the 6.3 old race car from you a couple of years ago.  :)
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

PMcG

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Re: Engines coming out. What’s a good power upgrade
« Reply #6 on: 06 October 2020, 10:23 PM »
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?
1976 450 SE
Diamond Blue Metallic / Navy Blue

rumb

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Re: Engines coming out. What’s a good power upgrade
« Reply #7 on: 07 October 2020, 06:23 AM »
Crossover pipe are a proven method of improving exhaust gas flow.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550