Can I get by without a head rebuild?

[rjcaptsean]

Some background:

The car ran decent but wouldn't pass smog.  (Probably due to the POs installation of two used Cats.)  I did the "mess under the intake" mod and purchased a new exhaust system, but haven't installed it yet.  I ran a compression test and all 4 cyls were withing 85% of each other.  Although, I didn't warm the engine up prior to the compression test.  No leak down test performed either.  

I did notice a suspicious rattle at the front of the valve cover, so I pulled the cover and the chain and gears are good.  I then pulled the front end off and all of the guides are worn, but not broken or crumbling.  Since I was into it this far and haven't found anything obvious, (although at this point I think the tensioner was the culprit), I decided to pull the head for a look-see, and to replace all of the obvious gaskets.  Here is what I found:





As you can see, the head looks great.  The valves are tight with no damage and no leakage.  The head gasket looks great, and the cylinders are all in good shape.  
Basically, what I would like to do is just clean it up, replace the headgasket and go as is.  I am afraid of getting into a head refurbishment due to the cost of guides, grinding, cam bearings, etc. etc.  
Any input?  Should I bite the bullet and rebuild the head or can I get by without it?

[dakon]

kind of funny you are asking this question.. i did what you are trying to do. and right now my head is at the machine shop...

there is a crack between #2 cylinder between the exhaust valve the large coolant channel, evidently this is a very common problem on our heads, the machinist knew exactly where to look, he said almost every head he sees has a crack between the exhaust valves and a coolant channel... doesn't look like you have any cracks which is good

my head also needed a valve job, and a re-surface.. someone had "belt sanded" the head to resurface it. this is supposedly a cheep way resurfacing the head....



From my experience, i would tell you at a minimum take it to a machinist, get them to dye check it for cracks, and pressure test it. if i would have done that. i would not have my head off again, after 1,200 miles after the rebuild.....


so far the cost for my head is going to be 450$.. they are going to call tomorrow and update me.

if the machinist you take it to gives it a clean bill of health, then i say go for it... also keep in mind they will be able to see/feel imperfections that you can not see over the internet.....


oh, and those damn exhaust valves are 61$ each from getbmwparts.com that was the least expensive place i could find them online.

if your guides are not in great shape, i would replace them.. i have a buddy who lost a head due to a broken chain guide.. i replaced all of my chain guides when i did my build, because i did not want to worry about 20 year old plastic that is in almost constant contact with a chain spinning at 2,000rpm+....

[monko141]

My suggestion is to pull the camshafts off, put the plugs back in, pour some cheap fuel injection cleaner onto the valves and see if it starts leaking through into the intake and exhaust ports.  It will tell you if you need to have your valves reground.

[rjcaptsean]

Drat!  You were the one I was hoping hadn't had any issues.  I guess I will have to bite the bullet and at least have them clean it and check for issues.  I looked closely at the suspect area you had and it looks pretty good.  Unfortunately I head out for a couple of weeks tomorrow, so I will have to take care of that when I get back.  

A question for you though.  Have you had any issues with the lower timing chain case?   I hear they are a bear to put back on once removed.  It looks pretty straight forward other than making sure it is positioned correctly to mate with the head.

[rjcaptsean]

My suggestion is to pull the camshafts off, put the plugs back in, pour some cheap fuel injection cleaner onto the valves and see if it starts leaking through into the intake and exhaust ports.  It will tell you if you need to have your valves reground.

Any issues I need to be aware of when pulling the camshafts off?

[B318M42W]

1/4 turn at a time on each bolt. hollow and fragile camshaft will break if unequal stress is applied. (or get the special tool that will hold them in place while removing the bolts) good luck!

[dakon]

 

A question for you though.  Have you had any issues with the lower timing chain case?   I hear they are a bear to put back on once removed.  It looks pretty straight forward other than making sure it is positioned correctly to mate with the head.

there were no issues when doing the original build. i am going to take the upper timing case to the machinist tomorrow. so they can machine the upper timing case as well as the head.. Dan didn't say anything about having any problems putting the bottom chain case on.. Right now i only have the upper timing chain case off, as the motor is still in the car, and i don't really want to pull the crank bolt...

I understand other members giving you ideas how to check the valve seats... however i would still recommend taking it to a machinist and get everything measured. this would have saved me almost 1,000$ ish... not to mention the time to tear down the motor to get the head off, and the time it will take for me to put the head back on and get it running again.

10$ for some injector ceaner.
200$ to "know" everything is good.... for me i would rather spend the 200$ and have no worries at all.....

but that is just me

[dakon]

i went by the machinists today, i got there just as they were talking the valve springs off, hung out until they got the head broken down enough to go to the welders...

need new exhaust valves, in addition to the stuff mentioned before..


if for some reason i decide to go with an S52 swap, i will sell you all of the motor stuff that i just bought for 1/2 of what i paid, if you are interested..
cam gears, timing chain, crank sprocket, chain guides sensors, alternator,starter,flywheel (jb racing) clutch (sacks) shifter (autosolutions)


if you are interested, again i don't know if i will do an s52 swap, as that will take considerably longer than just fixing the m42 (i think).... but i will give you first dibs on those parts if you are interested.


also all of those parts have maybe 1500 miles on them, 1200 of which are highway.....

[rjcaptsean]

Thanks for that!   I already have all of the guides, and the chain and sprockets look great.  Fortunately, the clutch looks magnificent.  I believe the PO thought the trans noise was the clutch, so looks like it was replaced very recently.  Not very much wear on the flywheel even.  The trans is bad though.    

Just called around for estimates on the cost of a 16v 4cyl valve job.  Ranging $400 from a guy who was incredulous that the 91 was 16v to $175 from a shop that knew it came from an M42.   Guess which shop I'll be calling on?

[lbreevesii]

I wouldn't be adverse to doing the seals and lapping the valves myself.  Clean the head throughly, remove the valves and lap each one,  have it all checked for wear/cracks, resurface and go for it.

[dakon]

Stopped by the machinist today, when it was at the welders the welder found a second crack in the head and fixed it.. also my head needs 4 exhaust valves, and all new guides.

My machinist found exhaust valves for 29$ each, and they aren't the cheap China crap.

if you need any exhaust valves rjcaptsean, just let me know, i will give you my machinists number and you might be able to get them from him, or he may tell you where you can get them.

just let me know.

[rjcaptsean]

I will pray that I don't, but thanks!

[dakon]

my head now needs all new lifters. i told them i was only willing to pay 200$ for a full set. dont know if that is realistic or not, but that is my price.


if they can not get lifters for 200$, do you want the head? its got 4 new exhaust valves, valve job, new exhaust valve guides, all new valve seals, machined, all you will need is your old lifters.

Anyhow let me know if you might be interested.

[BimmerJon]

rjcatsean, I think that all looks quite good, actually.  If it was me, I'd clean it up and put it all back together with some new gaskets.  Just check carefully for cracks, as mentioned previously.  My head also cracked between the exhaust valve seat and the coolant channel.

dakon, if you still need lifters I have an extra set I'd sell cheap.  Send me a PM if you want them.

[dakon]

Damn... i just ordered a set on monday!... 16$ each!....

Thanks though man!