Retighten Cylinder Head - Service

robertm · #1 08-01-2012

Hi
The Yanmar 2GM service process says retighten cylinder head (after first x hrs), which I doubt has ever been done on mine. Its now up to 800 hrs and I'm going to give it a go using torque and sequence settings I've got.

Do I have to slacken off, clean and oil all the bolts (in sequence) first before tightening and ;

Do I have to remove starter motor and try and view flywheel marks to do the valve clearances or (as I used to set the old car.. I had) can you view when the valves are rising and falling to set the gaps?

Any advice much appreciated.

klem · #2 08-01-2012

I highly doubt that most engines get a retorque on their head studs. I have done it on a few performance engines immediately after their first hard run but that is it, never on anything else. You are correct that to do a retorque, they need to be loosed a bit before being tightened. If they were properly lubricated from the factory, breaking them free and then going to torque should be adequate but you can certainly put on more never seize or whatever your preferred lubricant is. Personally, I wouldn't bother to do this unless I knew that these engines had a habit of blowing the head gasket but it is your engine.

You never need to see timing marks or use a timing pin to do valves, you can watch them as it sounds like you did on your old car.

Sea Dawg · #3 08-01-2012

800 hours? Leave it alone. Seriously. There's an old adage about if it ain't broke... that was based on a lot of good sense.

dabnis · #4 08-01-2012

Quote:

Originally Posted by Sea Dawg

800 hours? Leave it alone. Seriously. There's an old adage about if it ain't broke... that was based on a lot of good sense.

Totally agree. More than once I went back and tinkered with things and made more, unnecessary work for myself. If you are looking for something to do checking the valve lash probably won't hurt anything

Paul T

casey1999 · #5 08-02-2012

I plan to check valve clearance on my 30 year old Yanmar 3GMD (no idea how many hours she has but must be in the many thousands).

My plan is not to lossen the head bolts but just check torques is at least the minimum stated in the Yanmar manual. I would be afraind of loosening any thing with the potential of breaking the apparently now good head gasket seal.

Any comments on this procedure, or should I just leave it alone?
Regards

dabnis · #6 08-02-2012

Quote:

Originally Posted by casey1999

I plan to check valve clearance on my 30 year old Yanmar 3GMD (no idea how many hours she has but must be in the many thousands).

My plan is not to lossen the head bolts but just check torques is at least the minimum stated in the Yanmar manual. I would be afraind of loosening any thing with the potential of breaking the apparently now good head gasket seal.

Any comments on this procedure, or should I just leave it alone?
Regards

Maybe better to just check the valves and leave the head bolts alone?

Paul T

casey1999 · #7 08-02-2012

Quote:

Originally Posted by dabnis

Maybe better to just check the valves and leave the head bolts alone?

Paul T

Rodger that. I hate creating work for myself when trying to "fix" somthing that ain't broke.

dabnis · #8 08-02-2012

Quote:

Originally Posted by casey1999

Rodger that. I hate creating work for myself when trying to "fix" somthing that ain't broke.

How true!! To my detriment I was always "tweaking" things to try to make things "better". In many cases I made things worse. Nothing wrong with doing basic maintenance but if the basic package works and looks good it's probably better not to fuss with it. One of the best parts of owning Honda cars, motorcycles, generators, outboard motors and snow blowers is that they just flat work, right out of the box, no tinkering or "adjustments" necessary, and they don't leak oil, unlike many american made products I have owned. Being told by an american made car dealer "they all do that" when you have a problem is not a confidence builder. End of rant.

Paul T

robertm · #9 08-02-2012

Many thanks guys.
I'm going to leave the head bolts alone, and check the valve clearances. I think if Casey1999 has gone 30 yrs without doing that, I'm wondering how often that needs doing !!!

klem · #10 08-02-2012

How often you should do valve clearances really depends on the specific engine and how you run it. If you do them once and find that they are still good, I wouldn't worry about them very much. For example, in my pickup truck (cummins 6bt), I first checked them at 200,000 miles and none of them were more than 0.002" out so I don't plan to check them again while I own the truck. I have also worked on engines that were way out after 1000 hours.