Should I pull the head

[cat97628]

I have pulled my motor and trans to fix all leaking gaskets and seals as well as timing belt, water pump, etc. the question I have is should I go ahead and replace the head gasket? I have no signs of issue, so should I do it just to do it. I have the gasket and bolts.

[e30davie]

If you pull the head off, make sure you take the head somewhere to get checked over. At the very least get it cleaned properly. If will probably need some valve stem seals. This may cost you a few dollars.

No point pulling the head off without doing this in my opinion.

[Lugnuts]

If it ain't broke...

Saying that, if you've already gone to the trouble of pulling the engine and trans, now would be a good time to do it. As already mentioned, you would want to get the head checked for straightness and have a light skim/cleanup done on the mating surface. I believe this will require you to disassemble the head completely. It would also be advised to clean up the block mating surface as well, so the new gasket seals properly. Do not use any form of "scotch-brite" pad or scourer...just a razor blade, or gasket scraper tool.

What brand of gasket and bolts have you got? Replacing a good, working Genuine head gasket with a cheaper/inferior product might cause you headaches further down the line. You also want to be comfortable doing the torque + 90 + 90 degrees. Clean the bolt holes thoroughly etc, replace the 2 alignment dowels in the block...

[zaq123]

If you pull the head off, make sure you take the head somewhere to get checked over. At the very least get it cleaned properly. If will probably need some valve stem seals. This may cost you a few dollars.

No point pulling the head off without doing this in my opinion.

x2. If head comes off, both the head gasket surface and the block deck needs to be checked. I would also refresh valve seats and most likely EX valve guides will need to be replaced. Look at your valve stems...are they perfect?

[Jaxx_]

I think this depends on your time commitment and how much you want to spend. If you're truly doing it just to do it, I say don't bother. If you want to replace valve stem seals and inspect the valve train for wear, go for it.

How much of the head work do you want to do yourself? If you want to have the head cleaned and disassembled by a shop as well as replace the valve stem seals and regrind the valve seats, you're probably looking at ~8-10hrs of shop time. If you do it at home it's probably close to $40 in materials and similar time. Luckily on these motors you only have 12 valves.

When I was more broke than I currently I am I bought an E34 with a broken rocker and just checked the head with a straight edge stainless steel ruler and feeler gauges. After confirming it was within spec, just pulled the valve stem seals and valves and cleaned it all up with mineral spirits and the valves with a brass wire wheel. Jafromobile has a great video on how to do a valve job at home: https://www.youtube.com/watch?v=7GEmuQa3dPY

[zaq123]

Have you ever seen how valves and seats get conceived after lapping and only inner and outer edges make contact? Machinists can tell right away if head/valves were lapped as cutting machine makes initial contact with edges. Lapping compound gets removed from the edges fast upon the initial valve to seat contact. The compound which gets trapped in the middle, wears ditches in valves and seats. Check valve to seat contact for about 10 sec by lapping? ok. Lapping to correct anything? wrong approach to the problem.

IMHO, call machine shops and get a quote to cut seats, surface the head and replace valve guides. If you can afford it, this is the way to go since you have the engine out of the car.

If no, just let it go and hope it will last fore many more miles.

I think this depends on your time commitment and how much you want to spend. If you're truly doing it just to do it, I say don't bother. If you want to replace valve stem seals and inspect the valve train for wear, go for it.

How much of the head work do you want to do yourself? If you want to have the head cleaned and disassembled by a shop as well as replace the valve stem seals and regrind the valve seats, you're probably looking at ~8-10hrs of shop time. If you do it at home it's probably close to $40 in materials and similar time. Luckily on these motors you only have 12 valves.

When I was more broke than I currently I am I bought an E34 with a broken rocker and just checked the head with a straight edge stainless steel ruler and feeler gauges. After confirming it was within spec, just pulled the valve stem seals and valves and cleaned it all up with mineral spirits and the valves with a brass wire wheel. Jafromobile has a great video on how to do a valve job at home: https://www.youtube.com/watch?v=7GEmuQa3dPY

[rturbo 930]

I'd probably leave it. A few years ago when I replaced my motor, I was in a similar situation. I did all the gaskets and seals but left the head alone. I'd be more tempted to replace it if it's a motor with high miles, say, 250k+.

[digger]

Engine out, I'd pull the head to freshen it unless it was known to have been done recently. It Makes it run a whole bunch better that its worth it IMO. It's easy once you're in your position

[Jaxx_]

Check valve to seat contact for about 10 sec by lapping? ok. Lapping to correct anything? wrong approach to the problem.

Aren't we talking about a running motor that hasn't seen valve and piston contact? Everytime you pull a head you're going to get new valve seats and cut them? That's ridiculous. If the seat or the valve has pitting, OK--but otherwise, what's really the point? Aren't we just trying to remove any carbon or 1 thou of uneven wear?

Perhaps a new cam, rocker arms, and eccentrics as well? Where does the refresh end? I don't have a lot of experience building motors, so I am curious to learn why you think it's necessary to cut new seats on a running motor.

[redlightpete]

What’s the mileage, and how much oil does it consume?

[digger]

Aren't we talking about a running motor that hasn't seen valve and piston contact? Everytime you pull a head you're going to get new valve seats and cut them? That's ridiculous. If the seat or the valve has pitting, OK--but otherwise, what's really the point? Aren't we just trying to remove any carbon or 1 thou of uneven wear?

Perhaps a new cam, rocker arms, and eccentrics as well? Where does the refresh end? I don't have a lot of experience building motors, so I am curious to learn why you think it's necessary to cut new seats on a running motor.

He means lapping used valves and seats is not how you correct issues with seal and he is correct. If there is a valve to seat seal issue you get it fixed with correct tools and then if you insist you can lap to check contact position etc better clean thoroughly if you lap.

[zaq123]

Aren't we talking about a running motor that hasn't seen valve and piston contact? Everytime you pull a head you're going to get new valve seats and cut them? That's ridiculous. If the seat or the valve has pitting, OK--but otherwise, what's really the point? Aren't we just trying to remove any carbon or 1 thou of uneven wear?



Perhaps a new cam, rocker arms, and eccentrics as well? Where does the refresh end? I don't have a lot of experience building motors, so I am curious to learn why you think it's necessary to cut new seats on a running motor.

If seats are ok, absolutely no need to replace them, just cut them to get them back in spec, pretty standard procedure. Valve seats do wear out and get out of shape even though they look all pretty and shiny once you brush off all carbon. Same goes for valve guides. The point I’m trying to make is that the head needs to be checked and worked on with proper tools. Lapping away to get seats/valves in shape is no way a proper way to do things.

IMHO, 150k+ motor that is out of the car already should get valve seats recut, skimmed for good HG contact and valve guides checked and replaced if needed. Most of the above requires some expensive machine shop equipment. If the cam rockers and valves look good and the budget is tight...just leave it alone and hope for the best maybe. If pulling the head to do cam and rockers, do the whole thing the right way.


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[Andre3127]

I had very good luck with valve lapping. I checked my valves afterwards with prussian blue and the contact was excellent. (And no, before you ask, I'm not one of those fools who smears buckets of blue onto the seat. I'm a machinist, and I know how to use it properly). The seat was uniform, passed the spin and tap test, held water, and was ready for reassembly.

Will lapping correct roundness issues? No, but it will clean minor pitting and refresh the seat.

[e30davie]

We can argue about it all we like, but in my opinion if you are going to the effort of removing the head and replacing the gasket the head needs to be in perfect order when it goes back on - anything short of this is a waste of time.

And to me the best way to do this is to give it to a machinist and say ask them for a condition report and what they recommenced doing. They will clean it, pressure test, crack test it - all of the tests. Assuming it only needs minor work you will get it back in a few days in brand new order - install a new good quality head gasket - good for another 30 years. Im a big DIY man, but when it comes to this kind of thing, best left to the pros.

Last m20 i did this on had perfect compression test results and head looked very clean. It probably would have ran fine. On inspection it was found that every exhaust valve seal was stuffed, one valve was leaking slightly. For a few hundred bucks it is now in brand new order. 40,000km later and she is still running as strong as ever.

[cat97628]

The engine has 163k miles and hard to say how much oil it consumes vs leaks. I only drive the car a couple hundred miles a year and change the oil in the spring and in the fall. I am really torn on the taking the head off. I know doing it now is the correct way to go about it but I really do not have the time or extra money to put towards doing it right. I have a trip planned for the middle of October and need the car up and running. I would like to get it completed by next weekend and back in the car. I am then onto a dash replacement and new leathers.