Starting with a head gasket replacement this weekend

[eskimo810]

... bentley in one hand, genuine BMW gasket in the other. I've done some googling and research here on R3V, but I'm curious if anyone has any particular words of wisdom they could share with me. Any places to expect trouble, any modifications to the Bentley manual's instructions that might make my life easier.

I'm planning to take my time on this as I don't have work all week, but I'm interested to hear what people might have to say.

[jlevie]

My only words of wisdom over and above what is in the Bentley would be:

Take the head to a machine shop to be checked for cracks and surfaced. Have the valves ground and new seals installed.

Use a thread chasing tap on the head bolt threads in the block. Then wash them with solvent use an air gun to blow them clean.

Use new copper plated nuts on the exhaust studs. And new o-rings on the oil return tube.

[eskimo810]

My only words of wisdom over and above what is in the Bentley would be:

Take the head to a machine shop to be checked for cracks and surfaced. Have the valves ground and new seals installed.

Use a thread chasing tap on the head bolt threads in the block. Then wash them with solvent use an air gun to blow them clean.

Use new copper plated nuts on the exhaust studs. And new o-rings on the oil return tube.

Good stuff. Cleaning the head bolt holes is definitely something that I've been a little worried about. Any idea how much it would cost to have all the work on the head you mentioned done?

[mrgraphics]

Make sure you put new seals on the bitch tube when you install. I forgot them and wondered why the car dropped power from idle to 1500 rpm.

Change the camshaft seal. I opted not to because I was focused on getting the engine back together, and I have a small leak in the front of the engine. It's not dripping or anything, but my degrease effort is now tainted.

New gaskets everywhere - even for the connection from the exhaust manifold to pre-cat. I forgot to buy them, and had to install after the fact and it was a pain.

[jlevie]

The shop I use would charge me about $200 for surfacing and a valve grind. I take the head to them completely torn down and cleaned. So there is minimal labor on their part.

[eskimo810]

Make sure you put new seals on the bitch tube when you install. I forgot them and wondered why the car dropped power from idle to 1500 rpm.

Change the camshaft seal. I opted not to because I was focused on getting the engine back together, and I have a small leak in the front of the engine. It's not dripping or anything, but my degrease effort is now tainted.

New gaskets everywhere - even for the connection from the exhaust manifold to pre-cat. I forgot to buy them, and had to install after the fact and it was a pain.

I dropped money on BMW's cylinder head gasket set. So we'll see how that goes, I need to look up what exactly is included in it again.

The shop I use would charge me about $200 for surfacing and a valve grind. I take the head to them completely torn down and cleaned. So there is minimal labor on their part.

I see. Now if I was on a budget, and perhaps a little less ambitious in terms of taking the entire head apart; could I clean it up well and then a bring it to a shop to just have it surfaced (decked? is that the word?)? How important is the valve grind?

Not interested in doing things half-assed, just trying to simplify this whole project.

[997_rich]

Often times, people will turn the head over once removed, remove the camshaft, put the plugs back in and fill each "head" with some kind of solvent and see if it leaks throught the valves by gravity. If it leaks- lap the valves, if not-don't.

maybe do a leakdown on all cylinders to see where you're at before you start? that can help to give you a sense of how far you need to go.

[jlevie]

The main thing that affects performance is the head (i.e., that is where the power is made). So it makes no sense to me not to have the valves ground while the head is off. And the seals on a 20'ish year old head always need to be replaced.

Disassembling the head is a "piece of cake", though you will need a driver to push the rocker shafts out and a c-type compressor for the valve springs. In my experience a used head always needs to be surfaced, even if there hasn't been a head gasket failure. I presume that you are replacing the gasket because it has failed, in which case surfacing isn't an optional part of the task.

[bddog]

When you take the head off, check the gasket. Check the head. It is important to find the source of the problem. Often times it will be obvious. If you are lucky it will be a failed gasket. If the head is cracked or overly warped, you will need to get a new one.
A straight edge and a feeler gauge will tell you if the head needs to be shaved. You can only take so much off of a head before it becomes junk. I say don't surface what is already straight. Large sanding block and Emory cloth. Be careful while you are scraping gasket material, do not gouge it.
I have put a head back on without doing a valve job when I was in school and broke. I knew the valves were good though.
That being said, I would always get the valves ground. Replace all seals. Too much work and expense taking the head off not to do the valves too.
Be sure both surfaces are completely clean and straight.
Coat the cylinder walls with oil. Turn the engine over slowly, by hand. Wipe the crude off that collects at the top of the cylinder wall.
Take your time, clean everything thoroughly, takes pics for us!

[eskimo810]

When you take the head off, check the gasket. Check the head. It is important to find the source of the problem. Often times it will be obvious. If you are lucky it will be a failed gasket. If the head is cracked or overly warped, you will need to get a new one.
A straight edge and a feeler gauge will tell you if the head needs to be shaved. You can only take so much off of a head before it becomes junk. I say don't surface what is already straight. Large sanding block and Emory cloth. Be careful while you are scraping gasket material, do not gouge it.
I have put a head back on without doing a valve job when I was in school and broke. I knew the valves were good though.
That being said, I would always get the valves ground. Replace all seals. Too much work and expense taking the head off not to do the valves too.
Be sure both surfaces are completely clean and straight.
Coat the cylinder walls with oil. Turn the engine over slowly, by hand. Wipe the crude off that collects at the top of the cylinder wall.
Take your time, clean everything thoroughly, takes pics for us!

I've actually taken the opportunity to spring for a myster-e head! So I'll be sure to get some pictures.

[bddog]

From a "simplified" project to a ported and polished performance head, is quite a step. In the right direction I might add.
You still need to locate the source of the problem.

[eskimo810]

From a "simplified" project to a ported and polished performance head, is quite a step. In the right direction I might add. You still need to locate the source of the problem.

It is quite a step, but something I've been thinking about for a while. I figure it will probably happen this summer anyway so why not save the teardown and do it at the same time? As much as I'd like my car to be running right, right now, I'm trying to look at making this simple in the bigger picture as well.

And everything is weather dependent for me. I don't have work for weeks so I would start taking things apart right now to find the problem if it wasn't sleeting. Forecasts change, unfortunately.

[Andy348]

Definitely go for the Myster-E head. I recently replaced my HG and regret not picking one up.

Only information that I've received not found here is watch for the plastic head plugs. Your upper gasket set should come with 4 replacements, located at the front and back at the head (2 ea). Replace them in the same orientation as before.