Head Swap Question - PeachParts Mercedes-Benz Forum

bio350 · #1 09-17-2009, 06:54 PM

I have a couple #14 heads, a #17 and a #11. The 17 and 11 are off of 3.5L motors and the 14's are off of 3.0L motors.
Can I swap a head from a dead 3.5L motor and put it on a 3.0L motor?

MercFan · #2 09-17-2009, 06:58 PM

Quote:

Originally Posted by bio350

I have a couple #14 heads, a #17 and a #11. The 17 and 11 are off of 3.5L motors and the 14's are off of 3.0L motors.
Can I swap a head from a dead 3.5L motor and put it on a 3.0L motor?

Sorry, was it your 1991 that died - what happened to that motor?! I was going to take a look at a 1991 350SD this weekend near my neighborhood.

babymog · #3 09-17-2009, 07:19 PM

Going from the 3.5 to the 3.0 is pretty much a bolt-on. It is best to use the injection hard-lines from the 3.5L engine as they will match the angle of the injectors on the 3.5L head.

A #11 head? I haven't heard of that, pre-'87? Is that a non-turbo head?

bio350 · #4 09-17-2009, 08:10 PM

I might be looking at the wrong # for the 11 or just can't read behind the lines. I will double check.
I pretty much thought they should match up. I have everything from the two 3.5's.
I have one 3.5 that bent the rod, as was foretold. And I have one that is still good but it started blowing oil out through the intake. That is the #17 head that I am thinking of redoing and putting it on the 3.0L.

The 91 350SD had the 3.5L that was blowing oil through the intake and into the turbo. I pulled it and put in a 3.0L but it blew the head gasket and gallons of oil went out the tail pipe.

I also have a 92 300SD that had a 3.5L that actually bent the rod. I pulled it and put in a 3.0L also. It has been running great!

bio350 · #5 09-17-2009, 08:29 PM

Okay, I just ran out and took an inventory of what I have. I have 2 #14's that are on 3.0L motors and running great!

I have 2 #17's that are on the 3.5L motors sitting in the shed. And I have a #18 that is on the 3.0L motor that blew oil out the tail pipe.

Anybody heard of a #18 having issues? Should I rebuild the 18 or the 17? So many decisions.

babymog · #6 09-17-2009, 11:18 PM

I don't know much about the 17 vs the 18, and don't remember seeing it mentioned in the FSM. The 17 is updated to cure the combustion to water-jacket weakness issue, every subsequent update to the current #22 head (which I keep under my pillow when I sleep) surely had some changes but I don't have a source for that information. Could just be oil channels and other seal issues that the original design had to the chain cavity and the back of the engine.

Oh, also the #17 up all have the "oblique injection" change which puts the injectors at a slight angle compared to the #14, so the injectors (holders) are different, as are the pre-chambers and locking rings, the glowplugs, and the injector hard-lines. This was a change for emission reasons and allowed Mercedes to drop the ox-cat (previously necessary for CA emissions).

bio350 · #7 09-18-2009, 05:27 PM

I spent the day taking the 17 off the 3.5 so I think I will take it to the shop have it tested and whatever else may need to be done. Then I will pull the 14 off the 3.0 and replace it with the 17.
I am in the middle of building my garage which will become my "Benz Barn", so I think I will just wait until that is done. Yay!!, no more working on these things in the driveway.