Is my head gasket blown?

[rgafitanu@gmail.com]

I will be getting shims from Metric Motors although I hope to find a supplier on the east coast. I am not sure if the shims should cover for the initial suspected machining or only for this one that I know. If the machining is done only on the bottom, that doesn't change the rocker/valve geometry, only reduces the combustion chamber volume, am I getting this right?

[Tyler S]

Partially correct. Machining the top of the head also lowers the cam towers and affects the valve geometry. Machining just the bottom also slackens the timing chain. You want the shims to roughly equal the total amount of material (top and bottom) that was removed. If the head was also previously machined on top then you really should compensate for that as well unless the previous repair they used thinner valve thrust caps. The original ones should be 4.5mm thick. These might need to be changed as well depending on if valve work needs to be done.  Usually if the bottom needs to be shaved, the top does as well. You dont want to put the camshaft in a bind.
Wait untill the machining is done and subtract the total head thickness from the original to get your shim sizes. Make sure the machine shop is keeping track of the measurments. They will be able to tell you exactly what your going to need if their doing their job correctly.
If in doubt copy off related pages of the BBB for their reference if they dont have the specs.

[rgafitanu@gmail.com]

Tyler, the thrust valve cap is the piece that sits on the valve stem and the rocker pushes down on it, right? 4.5 mm would be the thickness of the groove bottom.

[Tyler S]

Radu, Correct.  If the valve and/or seat are ground, it moves the valve stem up higher into the head which is why you would need thinner caps. Determine all of this after machine work is done.

[Benz Dr.]

I use shims to also compensate for valve face and seat grinding, cylinder head stock removal, and maintaining tight timing chain. You need a minimum of .050 mm intake valve recession for proper valve to piston clearance so sometimes the intake valve seats need to be cut quite a bit deeper to make everything work. This will raise the end of the valve stem and decrease the basic setting between the rocker arm and the cam lobe. If the head is cut to near minimum specs and the valve seats are also cut a lot, even the thinnest lash cap may not work. Cam shims take care of all these problems because you may well be dealing with several at the same time. And, they're cheaper than a set of lash caps.

[rgafitanu@gmail.com]

When I insert the valve seals should the valves be in (to guide the seals) or out?

[rgafitanu@gmail.com]

I got the head back from the shop. They took 0.01" from the bottom. There was no machining from the top, the head was not warped. They took 0.01" because they welded the cavity and to clean the face.
I am reluctant (I respect your opinions) to shim under the towers. There was no work on the valves, seats or top, the valve caps measure 4.5mm so I believe the only drawback of not shimming is more slack in the chain and smaller combustion chamber. If I see the tensioner reaching its limit then the slack is too big. Increasing the combustion chamber to original would not happen with tower shims. All I am saying is the engine was running fine, the only difference is a smaller combustion chamber, the valve rocker kinematics has not changed.
What is the negative effect of turning the crankshaft using the camshaft sprocket bolt? I've done that for maybe 1/2 a turn before I read the warning here and I wonder if I should inspect the chain now that I have good access.

Thank you,
Radu

[ja17]

If your head was not warped, then you should be fine without the shims. Timing chain length is only altered .020"

Turning the engine with the cam bolt might cause the chain to jamb or jump timing. Just turn the engine with the crank bolt in the correct rotation and double check the crankshaft/camshaft timing marks.

[Tyler S]

They took 0.01" from the bottom. / The head has a thickness of 84.45 mm

Yes but don't forget there was previous machine work done that was not compensated for. Head measured 84.45?
I would add the shims.

[Benz Dr.]

On some engines where I've decked the block, planed the head, and did a valve job, I actually used two shims to give me .030'' cam lift. You can easily adjust the ball studs up ward to take up the extra gap at the valve rockers. If you can't install the timing chain because two sets make it too tight, remove one set of shims to lower the cam.
I would rather have a bit more clearance than I need than too little given the damage that can be done to valve guides from improper rocker geometry.

[rgafitanu@gmail.com]

I am taking my time now, knowing that this head is on it's last leg. I found that 3 of the 8 camshaft post head bolt (long) washers were not the thick chamfered type but the flat (like the valve cover bracket head bolts - short) type. So new washers are coming today and I plant to tighten the head bolts and mount the chain sprocket first. A block bolt hole next to cyl. 4 had dirt and the bolt that I was using to clean the holes was not going all the way down. Maybe this and the fact that the washer was thinner allowed for cyl. 4 leak; I was tightening that bolt against a fake dirt bottom.
Radu

[rgafitanu@gmail.com]

Now I am confused. The dealership told me there is a new part number for the thick washers and when I picked them up they were like the thin ones (by thin I mean 3mm while the others are like 4 or 5). I guess I will use these thin washers everywhere for consistency.

[ja17]

I will send you some originals if you like.

[rgafitanu@gmail.com]

Joe,
I would appreciate if you can send me 3 of those thick washers. For now I used thin washers everywhere, but I haven't started the car yet and I can probably remove them one by one and swap the washers before first start or with the first retorquing. It's 2 mm difference and my only concern is the bolt with a thinner washer reaching deeper in the block blind hole against the end of threads creating a false gasket tightening. My address is:
Radu Gafitanu
21 Chase Road,
North Dartmouth, MA
Let me know your paypal and how much they are.

Radu

[rgafitanu@gmail.com]

I stripped the thread on the small coolant bypass (between the head and the coolant pump) in the head. Should I Heli Coil it or just plug it?

[ja17]

Best to repair it. It is a std. metric fine thread. It helps bleed air out of the engine during coolant changes etc.  Not critical however, and I can be plugged off.  If plugged off, the engine coolant may be a little harder to "burp" during coolant changes.

[rgafitanu@gmail.com]

I repaired it and inserted a HeliCoil and it works OK. I was bleeding the chain tensioner and I get about 1/8" of play. I think I removed all the air as I get no resistance when I am pushing on the screwdriver for this small play (when I am pushing I can see that the plunger is moving too so it's not a shaft wear). To push it further it's almost impossible. Could it be that the tensioner spring got shorter and it's not extending to the full range of the tensioner? This could be causing the rocker noise that I was chasing.

[Tyler S]

Tensiner is fine. 1/8 inch play in the tensioner is normal. That is almost the exact distance the small steel ball inside has to travel before it seals itself against the orifice. If it were completely tight then the chain would have no way to accomidate length changes as the engine heats up. The spring inside is only to give the tensioner preload. The real work is done by the plunger and steel ball using hydraulic principle that liquid cannot be compressed.

[rgafitanu@gmail.com]

Sunday I finished adjusting the rockers, filled oil and water and started it. After a few cranks the gas reached the injectors and started right up. 10 minutes after reaching temperature and thermostat opening I stopped and retorqued the head bolts. Later after cooling down I readjusted the valve gaps (all of them were bigger). Went yesterday shopping with several in-town starts and stops. The temperature holds steady and water level is not dropping. I hope it's fixed. It appears to be running smoother than before although there is still some "rocker" noise. I am not convinced it is rocker noise anymore (I messed a lot with rockers, valves and springs), I should be listening to other 230's, it may be its natural noise. Thank you all for your help, I am grateful.
I still have one or two IP check valves that are leaking and I would have to get the newer version. It starts in 4 or 5 when warm for a few seconds.
I was pondering over the valve gaps, should one err on the + side or on the - side. If the gap is bigger your valve opening is shorter resulting in insufficient mixture in the cylinder or not all exhaust gas exits; some power loss? If the gap is smaller you risk the valve to stay slightly open as the stem heats and expands; compression loss? I am talking about this because it took me hours to get the "tug the gauge" feel, half of the adjusters were rounded and not responding to the special tool so I had to remove the rockers for every adjustment.

Thank you,
Radu

[tel76]

When you re-torque a cylinder head you further compress the cylinder head gasket, your valve clearances should be less not more.
I suggest you re-asses your procedure, torque wrench settings that you used, did you back off each bolt before re-torqueing?

[rgafitanu@gmail.com]

Eric, I respectfully disagree. The gasket is below the head and not in the tolerance "chain" of head-rocker post-rocker-valve-camshaft to alter the valve gap with further compression. There may be a small slack addition to the chain but that would change timing geometry and not valve gap. I believe the gap increase is due to the first engine run at temperature that made the rockers and valve caps to seat themselves properly but I could be wrong. I had the same torque setting of 70 ftlbs as my first torquing and there was further compression. However please bring some arguments I am very interested in all the details.

Radu

[tel76]

Radu,
You are correct, I should have given it more thought.
You cannot get the staff these days.

[rgafitanu@gmail.com]

It's been 200 miles after the cylinder head work and all appears to be fine. The car runs great and there is no water in the oil anymore. The rocker noise that I was obsessing about is gone however at start (cold or warm) there is still a "lazy" cylinder that needs 2-3 seconds or a push of the throttle to catch up. I believe that one of the injectors may have a lower pressure.
Yesterday I took some pictures. They all appear to be ok (consistent), plug 4 had no redness due to coolant but it had the ground (bent) electrode almost white (in contrast with the other). Could this be a lean condition from the injector?

PS. I realized that I didn't clean the plugs after the head work so they could still be showing some of the previous conditions.

[Tyler S]

Yes it is possible that you have a lean condition on one or more cylinders. However, replace or clean the plugs before you try and use them to isolate a condition. As you stated before, your IP check valves are most likely leaking down. Address this first as its most likely the cause of your cold start cylinder miss/studder.

[rgafitanu@gmail.com]

I pulled the plugs again after cleaning them and 500 miles and they all look the same. Maybe a little too lean (all of them)? Enriching the idle from the IP mixture screw would be sufficient, or the low/high speed IP mixture screws need to be adjusted?