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  #1  
Old 02-25-2019, 04:14 PM
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Will an 1986 420 engine and trans go into 85 380sl

Came across a clean 380so with the driveline out and bad engine { from timing chain failure} have a 86 420 sel with 133k on it . Any thoughts thanks
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Old 02-25-2019, 04:40 PM
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Quote:
Originally Posted by still at it View Post
Came across a clean 380so with the driveline out and bad engine { from timing chain failure} have a 86 420 sel with 133k on it . Any thoughts thanks

Your question:
"Will an 1986 420 engine and trans go into 85 380sl?"

Yes, use the CIS package from the 380.
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  #3  
Old 02-26-2019, 07:56 AM
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Have to swap the oil pan


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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,
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Old 02-26-2019, 10:07 AM
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Nice to know! Exhaust manifolds the same?
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  #5  
Old 02-26-2019, 11:35 AM
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Dom't know on exhaust. You also need the oil filter canister and mounting flange from the 3.8 SL.

Also 3.8 distributor and Ignition control unit.
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  #6  
Old 02-26-2019, 11:57 AM
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Yes, you'll need to swap the oil pan, oil filter housing and manifold. You can either go with the CIS-E and swap it over (there's not a lot of wiring, just computer, 02 sensor and EZL) or use the CIS injection from the 380SL
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Check out the W114, W115 enthusiast website.
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http://www.w108.org

Join the Mercedes W108 group
http://autos.groups.yahoo.com/group/mercedesw108/

My 280SL restoration

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Old 02-26-2019, 12:17 PM
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Quote:
Originally Posted by still at it View Post
Came across a clean 380so with the driveline out and bad engine { from timing chain failure} have a 86 420 sel with 133k on it . Any thoughts thanks


If you donít have the old engine, then youíve got to source the 107-specific parts.

Letís work on the list of parts that are not the same:
- driver exhaust manifold from w126 wonít work, might need passenger side too.
- oil pan from w126 wonít work
- ignition and injection system from a 1986 is not plug-and-play with the 1981-1985 cars. Easiest to take the systems from the 1981-1985 motor
- motor mount arms?
- oil filter adapter/housing?

Any others Iím missing?




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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,
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Old 02-26-2019, 03:03 PM
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Silly question but is the 420sel engine slightly more powerful than the m116 380sl?


Assuming the latter is a 4.2 liter engine .
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Quote:
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Going back to the original post: "Can you get the vac to blow instead?" No. Vacuums are low pressure so they by nature "suck" and nature abhors them.
1984 380SL
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  #9  
Old 02-27-2019, 09:46 AM
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Yeah, the 3.8 is rated as low as 155-165HP.

The 4.2L in USA trim was rated at like 200-205HP.

Also my understanding is all 4.2L cars are dual row chains. Now the OP has an 85 380SL so he had dual row to begin with. But in opinion if you've got an 81-83 380SL, the 86+ 420 motor is a great option, they're cheap, you're gaining nearly 50HP and you're losing the single row chain.
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  #10  
Old 02-27-2019, 11:17 AM
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Wow! Was hoping it wouldn't get to crazy . The injection and ignition are the only points that bother me .but it sounds doable
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  #11  
Old 03-03-2019, 12:17 PM
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It's all pretty easy once the engine is out of the car and before it's put in the next car. I get bored pretty fast working on all those little bolts on the oil pan. You really want to take your time cleaning out the socket head on each one. A stripped head in a tight spot is really annoying.

The other thing to watch is the transmission. They both bolt up, but if the 420 trans stays with it, you want both old and new home to use the same kind of speedometer hookup (mechanical vs electric). Not at all sure what little things would need to be done to use the original 3.8 trans with the 4.2 engine beyond swapping the modulator.

-CTH
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  #12  
Old 03-03-2019, 07:03 PM
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Quote:
Originally Posted by DieselPaul View Post
Yeah, the 3.8 is rated as low as 155-165HP.

The 4.2L in USA trim was rated at like 200-205HP.

Also my understanding is all 4.2L cars are dual row chains. Now the OP has an 85 380SL so he had dual row to begin with. But in opinion if you've got an 81-83 380SL, the 86+ 420 motor is a great option, they're cheap, you're gaining nearly 50HP and you're losing the single row chain.
Nice good to know.

Frank wrote a post about swapping the KE-Jet system for the earlier K-Jet one.

Wouldn't that be a bit of a nightmare to do? I was under the impression that you'd have to re-adjust the WUR to match the correct pressures for the 420sel then fiddle with the air metering screw to get it all to match up correctly.

Quote:
Originally Posted by cth350 View Post
The other thing to watch is the transmission. They both bolt up, but if the 420 trans stays with it, you want both old and new home to use the same kind of speedometer hookup (mechanical vs electric). Not at all sure what little things would need to be done to use the original 3.8 trans with the 4.2 engine beyond swapping the modulator.
-CTH
The 85 380sl spedometer is electronic so no issues there. Should all connect up. There's a recent post on Benzworld about modifying the spedometer for different rear ends too so changing differentials shouldn't be a big deal.
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Quote:
Originally Posted by Yak View Post
Going back to the original post: "Can you get the vac to blow instead?" No. Vacuums are low pressure so they by nature "suck" and nature abhors them.
1984 380SL
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