The internet (including this and other MB forums) is rife with inconsistent information as to the specifications, power and performance of the W117 engine used in the last version of the 108/109 sedans (and early 450s as well) sold in the US. Some sources contend that an 8.8:1 compression version making 230hp was used in some early applications, and an 8:1 version making only 200hp in later applications. Adding to the confusion is the fact that after 1971 the hp rating system in the US changed from the decidedly optomistic SAE "gross" method to the more realistic SAE "net" method (which in turn was much closer to the European DIN "net" system.
Sources noted below have confirmed that only the 8:1 compression version of the 4.5 engine was sold to the US market in 1972-73, and that its "net" hp was 190. The lower compression (and other detuning measures) were necessitated by our increasingly stricter smog regulations. In the early 1970s, NO manufacturer had the technology to make gasoline engines both clean AND efficient.
Compared tothe 1971 3.5 W116 engine, the 4.5 W117 version of substantially the same engine compares poorly at first glance. The 3.5 had 9.5:1 compression and made 230 SAE "GROSS" hp (DIN 200hp net!), but a closer look reveals that those extra 60+ cubic inches more that made up for the 4.5's diminished state of tune. The 4.5 made 190 SAE "net" hp at only 4750 rpm as compared to 5800 rpm for the 3.5's 200DIN hp (equivalent to 197 SAE "net" hp), and 240 SAE "net" lb. ft. of torque at only 3000 rpm as compared to the 3.5's 230 SAE "net" lb.ft. at 4200 rpm. Thus in real world driving, the 4.5 clearly had more usable grunt, and at a more relaxed pace. In keeping with the different power characteristics of the 4.5, Mercedes lowered the final drive ratio from 3.69 to 3.23, and employed a new, smoother 3-spd torque converter transmissioin in lieu of the older fluid coupled 4-speed. This combination was used in the 108/109 cars only in their last year of manufacture-1972. (Although the last 108/109 cars were manufactured in the fall of 1972, some leftovers were sold and registered as 1973 models.)
SOURCES:
1) M116/M117 engine service manual # S-6510-1916-13 published by Mercedes-Benz of North America, Inc.
2) Tom Hanson of Mercedes Classic Center confirmed that only one cylinder head and piston combination is applicable to US 4.5s in 1972/1973.
3) For a complete run down of all combinations of the M116 and M117 family of V-8 engines made by Mercedes-Benz between 1969 and 1991, both iron [early] and aluminum blocks, ranging from 3.5 to 5.5 liters (and utilizing 7 different compression ratios!), go to: .

__________________
Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
1959 Ford Thunderbird convertible/430
Past vehicles;
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang

I have wondered about this as well for my 72 280se 4.5. From what I have gathered the early build 4.5's had the higher compression engines that were rated at 230hp. My car is a June 1972 build and the owners manual does not state the engine power output. This manual has on the cover 280se, 280se 4.5, 280sel 4.5

Now, I have another owners manual (not sure which year) but this one states engine power output at 195hp SAE net method. This manual has on the cover 280se 4.5 and 280sel 4.5

There is a problem as OP indicated with changing method of measuring and quoting SAE HP and it all happened about time your car (and mine) were built. SAE switched from gross to net HP which is now very much same as DIN bhp (SAE about 1.4% higher) There is also the problem of Euro cars vs NA cars with different emision requirements.

OP is very hopeful to think his would be final word on subject Same discussion gets repeated over and over on the web.

What I did learn by reading the German Wikipedia link (used Chrome and had it auto translate) was that the 4.5L D-jet did come with two different compression ratios: 8.0 and 8.8. This link shows that the HP of the M117 in the W116 was lower in the US version. It does not say the compression ratio was lower, but I suspect it was 8.0 like another America bound M117 powered cars. In a book that I have, it says that 4.5L M117 DJets 1973-1975 had 8.8 CR in ROW with 225bhp DIN at 5000rpm. For NA they had 8.0 CR (71-75) with 195bhp DIN at 4500rpm. The later NA versions (75) with cats and egr power dropped to 180bhp DIN at 4750rpm.

I don't believe "early build" 4.5L M117s had a different compression ratio if they were destined for North America. And HP depended on how it was measured and quoted. 200DIN was figure I recalled seeing, but perhaps 190 DIN or 195 SAE HP using new method is also correct for early cars?

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

The Euro engines must have had other mods too, as a 0.8 point increase in CR will not give an extra 30 HP.

__________________
Csaba
1972 280SEL 4.5, silver

Here is what I've found from my own research:
There are one set of heads I've found on all 108 4.5's. I don't know if they're all the 8.8 or 8.0 but I assume they are the 8.8 based on the owner's manual my 108 had that said it was 8.8.
However, I have seen different sets of cams on 4.5 engines. I am unsure if perhaps the ones I've seen are for later models or if they were just replaced. I had 52/53 cams on my engine originally, that got toasted. I couldn't run the engine with them so vriefly I had a replacement set (57/58 IIRC) and they had lower power based on my ass-dyno than the 52/53 replacement ones I got later from the junkyard...

So the difference may be heads, may be heads and cam, or may be heads, cam, and the change in SAE ratings.
Note: I did grab a set of 4.5 heads off a w116 and the chamber measured larger than the ones on my original 4.5. That having been said, I did measure them at different times, so there may have been a difference there. I think Tony on the forums here has measured all the different 4.5 heads, though, and has noticed a measurable difference between the 8.8 and 8.0 heads.

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

The only 4.5 heads I have checked are from a K-jet 450 and they are 45cc's. I have looked at d-jet head pictures and it looks like the area that would be the squish area is recessed where the the k-jet heads are flat to form a squish area. Some engines have dished pistons and some are flat but have a negative projection of 3.6mm.

__________________
Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT

Page 00-020/3 of "Service Manual V-8 Engines M116 (3.5) M117 (4.5)" publication # S-6510-196-13 by Mercedes-Benz of North America, Inc. says the 280SE 4.5, the 280SEL 4.5 and the 300SEL 4.5 all had 8:1 compression, 190 SAE net bhp and 240SAE net lb.ft. torque. It stands to reason that if Mercedes could have met our smog regs of the day using a higher state of tune they would have used it on all then current 4.5 applications.

P.S. The engine identification # for the 300SEL (117.981) differs from that of the 280SE/SEL (117.984) because it includes a compressor for the air suspension system.

__________________
Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
1959 Ford Thunderbird convertible/430
Past vehicles;
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang

this is something I have always also been confused about. having both engines at my disposal. the M117 heads definitely have more chamber volume, but it is purely the increase in stroke of about an inch that would have pushed the compression ratio too high if they had left the heads alone and just reused original 116 castings. cast iron 116 heads are exactly the same they just have less chamber volume. also D jetronic 3.5's have pistons with valve reliefs cut in them, where m117's are a flat top design.

4.5 pistons are physically shorter then m116's.

I don't think the compression ratio has that much effect on those factory power ratings. some of that is definitely the ignition timing delay(retard) which is surely in place as they tested. also I think that the early cars must have all been only 8:1. there were no changes that I've seen on any of the motors until the revisions with K jetronic. K jetronic is a less efficient fuel injection system then D jet.

also though, if you take a look at all the earlier camshafts they all have quite a bit of overlap and duration(52-53)(46-47). but by the mid 70"s and into the alloy v8 engines the overlap and duration shrinks to nil. they had to keep increasing the displacement of the M117 to keep it competitive, with smog cams and Cats. by the mid-late eighties they had an engine of literally 1 full litre bigger(5.6), that generated supposedly a similar amount of power (239hp) as the stock 4.5 of 1972.

to another point as well the original cast iron collector exhaust pieces equipped on the W108/109 are actually very well designed stock pieces. with a split collector on the pass side, and a divided ram horn style collector on the drivers. and a true split system all the way back into what is a bosal glass packed muffler, its still got rather small pipes but the cross sectional area of both pipes combined is still greater then 3in. quite efficient for factory pieces.

__________________
____________________________
R107.043 Euro 350SL (parts)(crushed)
W116.024 280se (crushed)
W114 280 (m110)
W108.067 280se 4.5
W108.068 280seL 4.5 (crushed)
W111 220SEB coupe
W110 200D went to the crusher
W110 190D sold sold sold

1970 Rover P6B

Used to own(1950 buick,1969 lincoln MK3,4G63t colt,87 300ZX, 79 F100, 92 XJ40)

I think the main emissions reason for the reduced compression in '72 was the requirement to be able to run unleaded gas - which in those days, was only widely availible in regular-grade. I recall back then, and for a long time after, Amoco was the only retailer selling unleaded high-test.
During the '80s, I owned a couple early '70s Audis. The first was a '72, with a low-compression 1.8L four. Replaced with a nearly identical '71 high-compression version. In addition to the extra power, the '71 managed about 4-5 mpg better than the '72 - though I did need to run premium gas!

FWIW, I was in the Virginia Beach Pick-N-Pull this afternoon, and they had a 1978 grey-market/Euro 450SE. Small bumpers & cloth interior. Wonder about the power rating on that one. (All my MB info is back in Alexandria)

Happy Motoring, Mark

__________________
DrDKW

I think they reduced the CR to reduce NOx emissions. A 8.8:1 CR should be able to run a regular unleaded, maybe midgrade.

__________________
Csaba
1972 280SEL 4.5, silver