BTW, I did a search bt came up with nothing.

My cylinder head warped when it overheated. I took it to a local machine shop and they removed 0.7mm. The surface is now completely flat. Is 0.7mm too much to remove from the head?

The machinist said i should I use an oversize headgasket to make sure the valves will not hit anything. If I need an oversize head gasket what size should I use?

Thanks for your replies.






PICS UPDATED!!

 

that is a fair amount! but since you overheated your engine, it is within reason.

i would have to calculate how many cc's you lost in the combustion chamber to recalculate your compression ratio....but since i am working on my 3rd drink for the evening, that will have to be another time.

you should be ok, if you had v/p concerns.

 

Thanks...so do I gain compression by having it milled down but lose it by using a thicker headgasket?

 

Thats exactly right... I doubt that .7mm will do any damage to your engine... Having increased compression is a good thing if you drive your car in the streets... More low end tq and better throttle response... Only a marginal increase depending whether or not you decide to retune it or not if you stick with a higher compression or use a thicker HG.

 

Finish up that drink!!

 

Check mitsu specs in the repair manual... I think it's in there.

 

So, in other words if the mill is as flat as it can be and the headgasket fits nice and snug, I should go with the OEM thickness headgasket to increase compression and slightly thicker if I want to maintain standard compression.

I've also heard from AMS that spraying liguid copper around the headgasket might be a cheap way to ensure the HG fits nice and snug.

 

just use the oem gasket & spray some copper gasket if you care too.

the oem gaskets are amazing & are inexpensive too.

 

I was able to remove .015

 

WOT,

Thanks for following his thread. How is the copper spray sprayed on? Is it sprayed on both sides of the HG? Thanks again!

 

ok, .70mm is roughly .028 thousandths so not too bad. I dont know what the head gasket thicknesses are but I would think the "thicker" ones would start in at 1mm thicker then stock...don't know that I would worry about this too much. You would need to measure the volume of the dome in the head to determine actual compression ratio... maybe you picked up .5 of a point in compression here, ( I dont know) either way you are going to have to retune in some fashion to compensate..

 

BTW---the copper spray thing you might want to avoid.. Not to disparage any ideas here...just that it might work on iron heads and iron blocks but thats not what we are dealing with... with the aluminum heads you will be making a mistake and revisiting this all over again...

 

here are some pics of the mill. What I am concerned about is that they had to take off some of the edge of the valves and the fact that 0.7mm was taken off. You can also see where they had to take off some of the material around the bolts.






I might try for a thicker headgasket so that I can run the valves without hitting the pistons.

Or should I buy a new/used cylinder head so that I can be safe. It's so hard to do this when I can save so much money ($100 mill vs $1K+ cylinder work)

Anyone have any experience in engine reliability with cylinder warpage and mill downs?


Replies would be most appreciated

 

That's 3-4 times what the factory limit is for head resurfacing (8 thousandths, or .2mm). I have never seen a head with the valves cut along with the head. I personally would not run it. Not only do you have the compression ratio change concerns posted above, but your valve timing will be off noticeably as well (tbelt geometry changed).

 

wtf, they didnt even remove the valves when they milled your head???

the sharp edges will create hot spots = pre ignition & or detonation, let alone creating a cracking point to start.