1983, 380 sl heads 116 motor
 

Removed heads, now if a MB master mechanic would tell me what items are a must do while the heads are out it would be very appreciated.
I hate to not perform the proper repairs while heads are out.
How do you determine if valve springs, shims, valves are to be replaced, do you have to bead blast heads? I am thinking about just washing with degreaser only. Valve seat condition is determined how?

Motor mounts need replacement at this mileage? What reccomendations do you guys have?

I plan on driving the car for many years as a daily driver. 10k miles a year.

The dual chain upgrade was done about 100K miles back. now 175k miles.

Thanks for your response.

i would take
 

the heads to a reputable machine shop and have them inspect the valve seats, measure the valve edges for wear and the guides, and springs. then after acertaining what is needed buy parts and then have them grind the valves and whatever else is needed. and mill the head if it is not already too thin. straighten the head as needed. i would expect to pay from 3 to 500. for this all. including parts maybe.

tom w

Not being a master mechanic...

1. Now that they are off (a lot of labor), I'd take them or send them to a shop that knows how to do aluminum MB heads. I have the shop manual and there is a lot more voodoo and care involved then on, say, an old SB chevy head. According to what I've read, Liquid nitrogen is involved in installing the valve guides, fer goodness sakes.

I don't mean to scare you, but the shop manual says that helicoiling the block should be done when replacing the heads (no doubt, because the block is aluminum). The famous Road and Track article quotes an experienced mechanic who claims that with care, this is not required. Needless to say, make sure you have a good and accurate torque wrench. The gaskets aren't cheap, and you want to do this only once.

See this search:

http://www.peachparts.com/shopforum/tech-help/109469-560-sl-cyl-head-gasket-heli-coil-necessary.html?highlight=helicoiling+head

If you do it, be aware that there is a MB guide tool for this - the drill holes for the helicoils should be drilled one degree off, and this guide plate has this angle built in. Again, do you need to do this? I can't say.


2. Given my experience, your motor mounts have GOT to be shot. My car, 3 years newer and 1/2 the miles (with a more powerful engine, admittedly) and an apparent creampuff with 2 women PO's had one smashed and one broken. It's extremely difficult to see their condition without removing them, unless perhaps somehow measurements against an identical engine/car with a known good set could be taken with a ruler. I would do this especially because I think it contributes to the infamous "broken radiator neck" problem - the engine pulls on the radiator hose because it's sitting loose.

On the chain, my 0.02: Depending on what you want to spend, I'd do in this order:
1. The top chain guides
2. the tensioner
3. The tensioner arm
4. The chain

You do already have everything apart...

Eventually at your mileage and driving rate, you are going to have to deal with the lower guides under the timing cover, which is a major job (as opposed to what you are doing...heh heh).

I removed my left head at 100K miles and replaced a leaking head gasket. I did this succesfully without helicoiling. I also retorqued the right side. This was a very scary process since all of the headbolts on the right side torqued about 1/8 to 1/4 turn past the original starting point. My plan for helicoiling if I had to was to purchase a set of used junk heads and drill them out to make a drill guide. Otherwise the drill guide tool is $1600.00. I also toyed with the idea of making to single hole guides that I would move from hole to hole. One would have a 90° hole and the other would have the hole drilled at the proper 1.72° off of 90° angle.

As far as the head rebuild goes bring it to someone familiare with MB heads. Also I never recommend resurfacing an overhead cam head. There are people that can straighten them if they are warped. Resurfacing a warped head could leave you with a bound up cam shaft.

You will also want to replace your oil tube plastic fittings. At your milage since your chain replacement, while you have it apart re-do the chain and upper rails. Also every rubber vacume connector under the intake manifold.

John Roncallo

well
 

yes they should be straightened if warped, then lightly skimmed for an excellent seal.

tom w

Actually the service literature from M/B states that the 116, 117 cylinder heads should not be surfaced for warpage as they are soft enough to conform to the block when torqued. At high enough mileage to be apart most do need surfacing for corrosion, though.

With the engine apart for the head job, you should disassemble the intake manifold and replace the rubber rings that seal the upper to lower sections. With your mileage they are leaking vacuum-guaranteed.

Thanks guys, lots of good info, the head mating surface is in great condition as the block, the head looks warped but I imagine that torquing at the correct NM and timing will fit correctly once again.
I was going to replace the rubber parts below the intake manifoldI am making a long list of items that I plan on replacing.

if the head
 

looks warped without using a straight edge it must be a lot.

i would recommend having your machinist straightening it. it is not hard. he can put it on a "bending device" which probably has a proper name that i dont know, which will put pressure in a precise way, and put it in the oven over night. letting the bolts straighten it seems a little shakey to me.

tom w