As we know, the 86-89 300E/SE M103 engine used a closed-chamber head and dished piston to get 9.2 compression. The later years used an open-chamber head and flat pistons to get the same 9.2.

Well, just curious about what would happen if one installed the earlier dished pistons in the later open-chamber engine (yes, there is a valid reason, sorta. I can save $1400).
Compression would obviously go down considerably, but the specific questions are:

1. How much estimated compression loss, and estimated torque loss?
2. Would the pistons bolt in (same height, etc)?
3. Any tuning issues that would affect reliability and driveability, other than the obvious power/torque loss. Things like hot spots, timing, mixture, etc.

This is an anti-performance question I know; but she's just an old, pristine grocery getter, and smoothness and reliability are the objectives here; she never exceeds 1/2 throttle or 3500 RPM.

thanks,
DG

I would be intrested in what compression ratio you could get from flat top pistons and closed chamber heads. Instant high compression m103.

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87 w124 zender 3.6 - 3.0 kompressor in progress!
96 w124 e300 diesel - slowly being modded
98 w208 230 kompressor - m103 testbed SOLD.
96 s124 om606 superturbo diesel 508bhp

Well, we know the trough in the early piston is equal to the squish pad volume in the early head - since removing both kept the comp ration the same at 9.2. I've been doing some rough math (when I get my hands on one of the recessed pistons I'll get closer) but it looks to be somewhere in the 10cc volume difference in either the heads or the pistons. So, that would add up to a full compression point or more either lost or gained when mixing/matching.

Doe anyone have CC volume data on either head?
With that info, and confirmation of the pin to crown height being the same, the comp ratio could easily be computed.

DG

Lol....the 300SE is already dog slow with the rear end they put in it and second gear start.

Rather than cracking open the engine block, it would be far easier to put a 2.6 in it if you want it to be even slower . Dropping/raising compression by a point won't change the power drastically imo, I think it would work though?

But to answer your question, the smoothest, reliable, driveable engine is a STOCK engine.

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http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...

Come now, everyone has a reason to their madness...

He lost compression on No 1.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

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