What is the best way to skim the head on a ec300 to make sure it is true as I suspect I have a head gasket problem. I have my own lathe but not sure if I should machine it myself or leave it to an engine builder to have it done. What is the professional way of doing it? If it's machined on a lathe I don't fancy paying for something I can do myself. Thanks.
head skim for trueness?
- Thread starter andy176
- Start date
First I would double check if it is true or not.
If you have a glass table you can see it yourself. If you want to be 100% sure go to a professional with a surface plane (a precision plane to measure the trueness).
Then you decide what to do, if you have to skim slightly the head you can do it yourself on your lahte, then you have to check the compression and head squish to see if it is ok.
If the work is important (severe head distortion) probably it is better to have a professional, to rebuilt the o ring groove as well.
At this point I would check the trueness of the cylinder as well.
If you have a glass table you can see it yourself. If you want to be 100% sure go to a professional with a surface plane (a precision plane to measure the trueness).
Then you decide what to do, if you have to skim slightly the head you can do it yourself on your lahte, then you have to check the compression and head squish to see if it is ok.
If the work is important (severe head distortion) probably it is better to have a professional, to rebuilt the o ring groove as well.
At this point I would check the trueness of the cylinder as well.
Chuck your mandrel stock carefully and dial it to confirm it's running parallel. Then machine your spark plug thread and cut the shoulder on your mandrel nice and square. That will have the head running true when you skim it. The ridgidity of your lathe and tooling is important to prevent vibration and chatter.
If you are taking only a couple of thou to get it flat, your compression ratio and squish will hardly change. In reality the flatness (and surface finish) of the sealing surface is what's important.
If you are taking only a couple of thou to get it flat, your compression ratio and squish will hardly change. In reality the flatness (and surface finish) of the sealing surface is what's important.
(F5)
Gold Level Site Supporter
you can't check the head on a plate as its stepped down.
Even if it isn't warped its worth skimming it & reshaping the chamber. I cheated as I didn't trust my lathe to do flat & even, but I then used it to reshape the chamber adjusting the volume back to sensible. Burns much cleaner, wish I'd done it sooner.
Do a search for a thread I started on heads to read how I did mine.
Even if it isn't warped its worth skimming it & reshaping the chamber. I cheated as I didn't trust my lathe to do flat & even, but I then used it to reshape the chamber adjusting the volume back to sensible. Burns much cleaner, wish I'd done it sooner.
Do a search for a thread I started on heads to read how I did mine.
motopsycho87
New member
I just used a spark plug when doing mine 
motopsycho87
New member
I just put mine in normally, held it in a 3 jaw, then tapped the face until true
Cheers all got sorted machined a mandrel an screw cut it to a m14x1.25 spark plug thread an screwed the head onto it then checked it with a DTI and it was within 0.1mm so I don't think this was the problem I faced 0.1mm off it and it cleaned up perfect so new o rings and copper washers to be fitted just hope it was an o ring causing the over heating.
Sounds like your head wasn't running true in the lathe to start with I used the plug just to check my head with the dti but was running off I could have clocked it but was defeating the purpose and i could move it with my hand so I made a mandrel with a shoulder and ran perfect. Next question is what are the torque settings for the head studs? Also is it best to build it with the o rings dry or with grease or with three bond sealer? Thanks.
