Compression problems - please help remedy

[thysonsacclaim]

There is also no point in removing the head unless you are prepared to do a valve job as well. The guides will almost certainly be worn and the stem seals will need replacing.

This is where the dollars come into play.

TJ, et al: I appreciate you letting me know about what I may have to face when I open it up. However, I have a few questions for you if you don't mind.

1) Would I be better off just buying new valves or searching for ones in better condition? Cost-wise (without skimping), what do you think I should do? Or, would I be able to make the basic repairs now (R&R heads, replace chain stuff and gaskets), and do the valves at another time? I know it seems stupid to open it up twice... I'm just wondering if I could stretch the process out, but I don't want to be a cheap skate, either.
I would like to take pictures of what I find and ask your guys opinion, if you don't mind. I believe we'll begin the 'rescue operation' tomorrow.

2) What's a good way of judging the condition of the valves? Is there a test I can perform to see the wear on the seats? Perhaps allowing a liquid to sit inside, and see how much... if any... leaks out?


As you can see... I'm a little out of my comfort zone here. 




To be honest, I'd really love to just pour infinite amounts of money into the car, but it's not realistically possible for me esp being a student with little income. This is a labor of love, and I want to do it right... but I don't want to drown doing it either.

[TJ 450]

I would just play it by ear, but expect the worst and you may be pleasantly surprised.

Seeing as you're on a student's budget, I'd be inclined to go along with the liquid test like you suggest... if nothing leaks past, I would reckon the valves are sealing well enough. You could probably get away with just stem seal replacement if everything looks reasonable.

I guess it's not the end of the World removing them again, later down the track.

Tim

[wbrian63]

From my experience a "valve job" usually involves the following:
Replacing the valve guides
Replacing the valve seals
Grinding the mating surface of the valve
Grinding the mating surface of the valve seat
Reinstalling and lapping the valves to the seats with some lapping compound (not all machine shops go this far).

Unless you have issues like a cracked valve seat or a bent valve, most heads can tolerate a valve job without the requirement for expensive part replacement.

That being said, we are talking about an MB. The guides (16) and seals (16) might be expensive. I have no knowledge of this.

Good luck

[thysonsacclaim]

I checked the chain stretch just now.

We turned everything clockwise until the Right Cam shaft marker lined up with the mark on the gear. I then checked the Left side, and It was nearly perfectly aligned as well.

We then looked at the balancer. It shows about 1 degree of stretch.

Also, I checked the chain for a master link. It does not have one.

How can this be the original chain and only have 1 degree of stretch on it?!



The chain has a good deal of deflection on the top side. In fact, it has been chewing into the cam assembly and the valve cover. I'm not sure why it would show such a low amount of stretch on the balancer, though.

[TJ 450]

That's odd, chewing into the timing cover/ valve cover is a sure sign of a worn chain, I would have thought.

Maybe someone has altered the valve timing previously.

Tim

[thysonsacclaim]

Yes... indeed.

I'm in the process of pulling out the radiator and everything else to get a better look. I think when everything else is off, I'm going to check the stretch again by rotating it several times over and checking it again. Something has to be amiss.

I can't imagine that it wouldn't be stretched and make marks on the covers. It makes no sense.

[s class]

I've seen this thread late in the game.  It is fairly common that when chains get very stretched, mechanics advance the cam sprockets by one tooth.  So the indicated stretch (by the method you are using) is low, but the true value is the 1 degree you observe plus 16 degrees for the extra tooth of advancement. 

The number 3 spark plug's clean condition is further confirmation of water leaking into that cylinder - the water vaporises and steam-cleans the combustion chamber.  When you open the motor you will most likely find that entire cylinder is very clean inside. 

[thysonsacclaim]

That makes a lot of sense s class. Thanks for the info.


We have removed most all of the front dress now and tomorrow will begin removing the heads. I am leaning towards replacing both gaskets since we will have everything apart anyways... it will depend on whether or not I need a valve job done to the right bank.