Well you must have gotten the timing off, I'd start by timing it.

Not sure what the chain drives on an M103, but getting the crank and cam on the timing marks would be a good start. Is the distributer driven off the chain?

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Ron,

Something is wrong, be it major or minor. Do not run car until you have performed your checks.

Like Tony said, maybe you just whacked the plug while the head was off the motor.

Note to all: remove all plugs, injectors or other things from the head that you may have to before removing it. It is much harder to after the fact. I have a nasty scar from when I was 16 from pulling injectors off a VW diesel head because I was too much in a rush to remove them before pulling the head.

Regardless, you can not assume this as you have noises and a damaged plug.

Pull valve cover, pull all spark plugs, set crank and cam to TDC. Do the marks line up? Let's hope they do, if not timing must be reset, but more importantly, how many degrees/teeth are they off? I think 2 teeth out, and the valves are hitting the crowns of the pistons. Not an m103 expert. Let's assume timing is correct and continue.

Next you should assess if you have FOD (foreign object debris) in the cylinder. This could be a nut, rag, bottle cap, who knows what. A borescope would be ideal right about now. You could insert a fine magnet through the spark plug hole. May get lucky. Back track your steps. How careful were you? What are the chances you let something fall in? We all make mistakes, trace your steps.

If by whatever means you have did not find any FOD, crank the motor over by hand. Listen as you do this. Any strange sounds? Feel for resistance, does something feel choppy or abnormal in the motor?

If all seems good, crank the motor over with the starter, plugs still out. A remote starter switch is ideal about now. That way you only activate the starter, no fuel or ignition, and can stand by the motor and listen. If all sounds good excellent. Also you can move about the engine bay listening to the motor from various vantage points.

All this time you will have the valve cover off. Now you can check to see if you are getting oil pressure to the camshaft, lifters, etc. Ensure nothing falls into the head while the valve cover is off.

Assuming all is well, I would do a compression test for grins. Good to know where things lie. If you can do a leak down test, even better.

If all checks out for the good, bottom it up and give it a fire. Listen carefully. Keep fingers crossed.


OK, now onto possible bigger issues. This is the 3rd head gasket in 153k miles? Something is not right! Warped head, poor installation, improperly milled head are all initial thoughts.

Here come the questions:

When starting the motor after this head R&R did you ever get oil pressure? If so how much?
Why was the head pulled the first time?
Did the car ever overheat?
How long did the last gasket last?
Was the head serviced by the machine shop when it was off the first time? (as it seems it was not this time?)
If so, was it checked for warpage and/or was it milled?

FWIW, if the head was milled too far down interference can happen. Seen it before on a 603. Also have seen a head that was not milled straight. Head gasket blew in less than 10 minutes on that one. That was an m103 also. A good machinist is worth his weight in gold!

Take a deep breath. Clear the mind, and approach this systematically. It may be something insignificant, but best to do your homework to be sure. Best case all is well, worst case the head comes off again.

Lastly, before cranking it over more, when you pull the valve cover, if there is no oil on the cam, followers, etc, you really should put some assembly lube on those bits. Standard procedure during assembly. STP works in a pinch, Motor oil if in an even greater pinch. Something is better than nothing. WD40 will not cut it.

Let's help Ron figure this one out ILUVMILS.

Hatteras, the distributor rotor is driven directly off the cam. It is not like the earlier motors.

__________________
Regards,

Mathieu J. Cama
Old World Automotive
Lawrenceville, GA
service@oldworldauto.com

Specializing in high caliber repair and mechanical restoration of vintage Mecedes-Benz.

www.oldworldauto.com

you have given a good thorough descriptoin of all steps necessary. My only further comment is to ask how a valve can hit a spark plug if the plug is the right length? Seems impossible to me.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

not the valve, FOD or the piston. head has been milled too much, piston comes up, hits plug. chances are slim of it, but may be possible depending on how the sp. plug is oriented. like i said, not an m103 expert.

__________________
Regards,

Mathieu J. Cama
Old World Automotive
Lawrenceville, GA
service@oldworldauto.com

Specializing in high caliber repair and mechanical restoration of vintage Mecedes-Benz.

www.oldworldauto.com

When I saw the picture of the damaged spark plug, this was the first thing that came to mind. The more I think about it, the more sense it makes. That's why I asked if the plugs were installed for the duration of the job.

If there's any doubt about a foriegn object in the cylinder though, there are a few things you should do before installing a new plug and starting the engine. Using a borescope would be ideal, but since that's not gonna' happen, try this (I'm assuming you have an air compressor). Connect a piece of rubber vacuum line to an air nozzle. Put the vacuum hose into the cylinder and blast away. Keep a close eye on the spark plug hole to see if anything comes out. This may not get everything out (if there's anything in there), but you'll know right away if there's a problem. I've used this trick many times to clear debris from OM606 diesel cylinders, after drilling out stubborn glow plugs.



Incorrect engine timing can't cause piston-to-plug contact. Piston-to-valve? Yes. Piston-to-plug? No

As for the distributor, the ignition rotor is driven directly by the camshaft.

Thanks to all who have been kind enough to offer me advise and suggestions on how to deal with my situation.

Well, from reading and thinking about situation I decided I must have managed to get something in the cylinder that should not be there and the only way to know for sure and to assess damage was to remove head. So I did that.

Piston, cylinder and head and valve seat where damaged. The damage was caused by the small breather hose that goes from the intake manifold to valve cover which has those two metal clamps. The clamps did the damage. It is apparent I was not careful enough when fit the head to the block. This is the first time I did a head gasket replacement, so anyone else who does one for the first time I'd have to recommend just removing that little breather hose when you fit the head to the block, I suspect the pros remove it or are just more careful.

I do have a parts car, 1992 300 E with about 15K less miles on it than the engine I ruined in the 1992 300 TE. So everything should be the same except for the tandem power steering pump on the TE which runs the self leveling system.

I'm wondering if the transmission for the E model is the same as the one for the TE.

Hopefully I can swap engines without screwing anything up. I'm not a professional mechanic but I've got a good bit of experience and feel pretty stupid for not being careful enough when I reintalled the head.

Dude....I feel for you. I've made plenty of mistakes over the years, so I know how you must feel, but don't sweat it. Maybe there's hope. What kind of damage did you find? If the piston didn't crack, the damage may be limited to the cylinder head. If so, it's possible it can be repaired. If a valve seat didn't get hammered it might be easier than you think. Don't make a bad situation worse. Assess the damage and proceed accordingly. Keep us posted.