What best compression ratio for my AMG "replica" euro 5.0 M117? - PeachParts Mercedes-Benz Forum

GGR · #1 09-08-2010, 08:51 PM

Here is the story:

I have a euro 5.0 M117 out of a 450 SLC 5.0 that I have mated to a manual transmission and fitted with Megasquirt fuel & spark (EDIS) and knock sensors.

The engine is stock otherwise and I was planning to fit the whole thing in my '62 W111 coupe when someone on another board came with some AMG replica camshafts that are made out of stock ones reground according to the specs of the cams he has on his Genuine 5.4 AMG engine. These are marked 50.1.P and must be fitted with mechanical lifters that I have also sourced. Other comparisons with that Genuine AMG engine have shown that the work done on the 5.0 heads make them very comparable to the later 560 heads: similar port dimensions and similar bigger intake valves. So I have also sourced some 560 heads that I will be having checked and polished. The enine is also fitted with the original 450 SLC 5.0 very nice tri-Y exhaust manifold and downpipes system. After all that it would be a pity to keep my stock 8.8:1 compression ratio when these AMG had 9.2:1 and 9.4 CRs. I have seen some 9.2 compression ratio pistons on Ebay Switzerland and I also believe that the later 500 M117.965 came with 10:1CR pistons.

I am tempted o go with the 10:1 CR pistons especially because the Megasquirt fuel & spark (EDIS) and the knock sensors will manage that higher CR well with 93 grade fuel.

I nevertheless would like to get your opinion on the subject. The car will be used on open roads as a daily driver, including traffic jams etc.

Thanks in advance!

JayRash · #2 09-09-2010, 01:28 AM

go with 10.0

Turbo E320 · #3 09-09-2010, 01:43 AM

Hell with megasquirt and 93 octane you could handle up to 12.5:1 reliably.