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How not to adjust valves

Posted by Bob in Everett 
August 10, 2013 08:43PM
I should have known better. It just seemed like it was so convenient to adjust the valve clearance before I put the head on the car. It was on the work bench so I started checking the valve clearance, rotating the cam to the correct position and setting the clearance. Assembled the head onto the car and it ran but the idle was a bit lumpy.

After checking everything else I could think of, I opened up the valve cover and took the air dam off the front so I could rotate the crank. The valves were all pretty tight so I adjusted them all and did a compression check or each cylinder. They were all about 185 psi. Reassembled the whole thing and started it up. The idle was perfect. Also went for a short drive and it seemed to be much more like normal power.

Just have to change the seals on the transmission and maybe my oil leaking days will be ended for a short time anyway.

Bob in Everett
August 11, 2013 11:46AM
that' kinda odd. You would think your approach makes perfect sense as the cam is in the head. Wonder what could have changed?

alan
August 11, 2013 06:39PM
Apparently when it is all bolted down on the block, it is a litlle different shape than when on the bench. Like you, I was thinking that if it is flat on the bottom that it will not be changing shape when it is bolted down. But it sure did.

Bob in Everett
August 11, 2013 07:34PM
Along those lines, is a head supposed to be torqued down on the block before cam and cam train is installed? Your initial approach makes sense from a manufacturing standpoint unless they do assemble it before, install on the block and then adjust?

alan
August 11, 2013 10:56PM
It looks like disassembling the cam and rocker arms from an E-30 head may be impossible while it is on the engine. The directions in the Bentley manual are not very detailed about getting it apart or putting it back together. I have some interest in disassmbley of my old head just to try and find the crack, or what ever allowed the leak to occur. The cam appears to be badly worn and I am thinking it is because of the coolant in the oil. I drove it that way for about 2000 miles over the course of over a month.

Bob in Everett
rkj
August 12, 2013 09:35PM
Quote
Bob in Everett
It looks like disassembling the cam and rocker arms from an E-30 head may be impossible while it is on the engine. The directions in the Bentley manual are not very detailed about getting it apart or putting it back together. I have some interest in disassmbley of my old head just to try and find the crack, or what ever allowed the leak to occur. The cam appears to be badly worn and I am thinking it is because of the coolant in the oil. I drove it that way for about 2000 miles over the course of over a month.


Hey Bob, The valve adjust from bench to motor doesn't surprise me- we're only talking thousands here.

I've heard people changing out cams and valve gear while the head is in place, on the motor but why anyone would want to do such a thing is beyond me...

These heads have a reputaion of opening up (and leaking in this area) even on older motors with higher mileage, it's just a casting defect. My 325is has 230k+ so I guess I'm safe eye rolling smiley

What did you finally get for a replacement? Did it all pan out in the end???

Cheers, Rick
August 12, 2013 10:49PM
So, to repeat part of the story...I found when I took the thermostat housing off the original head to put on the replacement head, it rattled...it should not rattle...so I inspected all the ports and saw that a part of the thermostat had broken off and was flapping up against one of the inner ports, not sure exacly which way the water flows through the port but I suspect that the flow was not going where it was supposed to. Consequently the engine may have been unevenly cooled and that may have been contributor to the crack. I have 228k miles on the engine so it is probably getting close to "high mileage" category. My gas mileage has suffered for some time for no apparent reason and the plugs were getting some kind of deposit on them. With the new thermostat and replacement h

After taking the head off twice, I can see why it would be attractive to take the cam out with the head still on the car. Getting everything disconnected and unbolted is a long process. And it would save the cost of a head gasket kit and new head bolts. A machine shop I went to for advice wanted $650 to disassemble and resurface the head.

If there is a casting defect, perhaps a weld repair would be possible.

Bob in Everett
rkj
August 13, 2013 11:13PM
Quote
Bob in Everett
So, to repeat part of the story...I found when I took the thermostat housing off the original head to put on the replacement head, it rattled...it should not rattle...so I inspected all the ports and saw that a part of the thermostat had broken off and was flapping up against one of the inner ports, not sure exacly which way the water flows through the port but I suspect that the flow was not going where it was supposed to. Consequently the engine may have been unevenly cooled and that may have been contributor to the crack. I have 228k miles on the engine so it is probably getting close to "high mileage" category. My gas mileage has suffered for some time for no apparent reason and the plugs were getting some kind of deposit on them. With the new thermostat and replacement h

After taking the head off twice, I can see why it would be attractive to take the cam out with the head still on the car. Getting everything disconnected and unbolted is a long process. And it would save the cost of a head gasket kit and new head bolts. A machine shop I went to for advice wanted $650 to disassemble and resurface the head.

If there is a casting defect, perhaps a weld repair would be possible.

I meant where did you get a head replacement and what was it. I don't think you can fix an (a leaking) alloy casting no matter what the process it is.

Rick
August 14, 2013 07:56PM
The head came from someone who claimed it is an "i" head from a wrecked car. It seems to work well. The cam is in good shape. A lot better than what I had.

Bob in Everett
rkj
August 14, 2013 10:53PM
Quote
Bob in Everett
The head came from someone who claimed it is an "i" head from a wrecked car. It seems to work well. The cam is in good shape. A lot better than what I had.

Sounds like a good choice. Good luck Bob smileys with beer
August 16, 2013 09:24PM
Now I just have to tackle the leaky transmission. It is tempting to take it out and replace the clutch and front seal too. I am sort of into "if it ain't broke, don't fix it" mode but the constant drops of oil on the parking place is annoying. If the front seal started leaking I would be really annoyed.

Bob in Everett
rkj
August 16, 2013 10:07PM
Quote
Bob in Everett
Now I just have to tackle the leaky transmission. It is tempting to take it out and replace the clutch and front seal too. I am sort of into "if it ain't broke, don't fix it" mode but the constant drops of oil on the parking place is annoying. If the front seal started leaking I would be really annoyed.

Have you cleaned the vent?
August 17, 2013 12:03PM
Vent??
what vent? Is that where my leaking oil is coming from? Not the shifter seal or rear seal?

Bob in Everett
rkj
August 21, 2013 09:31PM
Quote
Bob in Everett
Vent??
what vent? Is that where my leaking oil is coming from? Not the shifter seal or rear seal?

The transmission has a vent on the top of the box, in the middle right behind where the bell housing would be (our transmission is a one piece casting as you know). The vent is a domed button you can put a bent paper clip through the middle, where the hole is. Sometimes the vents clog up creating presure forcing oil to leak out of all kinds of places. I've found access is easier from the engine bay on the starboard side. It's a sneak job but possible :wavey:
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