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Old 10-23-2000, 11:54 PM
John Stephens
Posts: n/a
I have a 1971 350 SL (euro version) and need some more understanding on the serial numbers. Can you suply info or confirm what i've figured out to date? The numbers i have are:
chassis w107.043-12-002948
w107 - wedge style body
043 - model 350 with 3.5 L engine
1 - left hand drive
2 - automagic trans
002948 - number 2948 off the line

Engine 116.982 12 802112
116 - 3.5 L
982 - don't know but suspect efi vs cis
12 - same as chassis
802112 - serial no.??

Can you supply HP (sae) and torque info on this engine??

also on cold starts the engine cycles between 600 and 1800 rpm until it's warm. Was this a feature for faster and mechanically better warmups or is there something wrong with the vacuum / efi connections?

Is timing chain stretch a problem with this small block V8??


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Old 10-24-2000, 12:12 AM
A. Rosich's Avatar
Registered User
Join Date: Nov 1999
Location: San Jose, Costa Rica
Posts: 883
Your chassis significance is O.K. y

Your engine, if this book is not mistaken, it should be as follows (116.982 12 802112):

1= Gasoline engine
16= Engine type
982= Engine model

1= Left hand drive
2= Auto transmission

802112= Serial Number

116.982 Engine details:

V8, 92.0 X 65.8 Bore x Stroke (cc)
3,499 displacement (cc)
9.5:1 Compression ratio (9:1 after 1979)
5,800 max rpm
Model applied: 350SL/SLC
Torque: 29.2 mkg @ 4000 rpm (231.5 ft/lb)
Power: 200hp (DIN) @5800 rpm (230 hp SAE)
Units manufactured:
350SL 15,304 units from 1970 to 1980
350 SLC 13,925 units from 1971 to 1980

Hope the information is useful.

A. Rosich
E320 T 1995
S320 1998

[This message has been edited by A. Rosich (edited 10-24-2000).]
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Old 10-24-2000, 07:56 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
The condition you describe of idle surge is very common in 3.5 engines. Your motor is running too fast. It is entering into a decel cut-off cycle.

Decel cut-off is a condition where injection is discontinued. The purpose is that while driving and decelerating (foot off the gas)no fuel will be delivered. This has been universal on all FI engines since those first D-Jet cars. Here are the conditions for decel cut-off on your engine (from memory so the numbers are approx): throttle closed, engine running more than 1800 rpm. Decel stops when the engine speed drops below 1200 rpm). Thus in your case you have 1800 rpm and get decel cut-off - then at somewhere around 1200 it cuts back on (it often drops much below 1200 in actuality), then the cycle repeats.

The 3.5s were the first MB D-jets and they had the criteria to close to actual conditions and your experience is common. The engine also was very sensitive to timing and a few degrees extra (which helps everywhere else) causes too high of a cold fast idle. The aux air valve also winds up setting the cold idle too high often.

To test my hypothesis just lower the idle or disconnect the throttle switch (the computer won't know the throttle is closed and decel cut-off will stop). The final answer will be achieving the right adjustments or replacement parts to keep the idle down.

Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
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