What is the distance between the valves and piston at their closes point?

[91orangeGST]

I just got my head milled down 30/1000 of an inch and I was wondering if I needed a thicker head gasket than stock. Also what is the distance between the valves and the piston head at their closes point? 91 4G63T

Kyle,

 

[Suparata]

Why did you have to remove that much material?

 

[91orangeGST]

I sent the head into a shop to get it rebuilt and the guy said he would increase the compression by deminemising the combustion chamber. So thats why. What is the average amount taken off?

 

[Suparata]

Taking a lot of material off the head surface is the last thing you would do to increase compression and I believe there is something else behind your machinist decision. No machinist would remove that much material so I think you were kinda screwed over.
Did the head go through a bad overheat? Check the camshaft journals for straightness before doing anything else.

I will tell you the valve-to-piston clearance if you tell me that the head is not warped.

 

[91orangeGST]

I dont know what the he was thinking, but he didnt mention the head being warped. The reason why I am asking this is because I just installed my head on my rebuilt block and it is makeing a loud ping by the number 4 cylinder, so I popped the head off and their are a few marks on the piston head! So I figured that was the only way it is possible because the valves arent bent and the springs also arent stuck.

So what is the clearence for a normal head?

Kyle,

 

[Suparata]

Minimum clearances between the valve and piston should be 0.080" on the intake valve, and 0.100" on the exhaust valve.
Depending on the cams manufacturer, minimum clearances required may be 0.100" on the intake valve, and 0.125" on the exhaust valve.

Piston to valve clearance should be checked when the valve gets the closest to the piston and that is during the period in the cams timing known as the "overlap".
Mitch.

 

[1fast97gsx]

not only could removing too much material cause piston / valve contact ... but it will also throw off cam timing. I'd get a thicker headgasket.

 

[tmizer]

ditto Suparata and 1fast97gsx:

0.010 inches/1000 rpm is a rule of thumb for heavy valvetrain V-8's. Suparata lists Mitsubishi factory manual numbers I believe, which is for stock valvetrain @stock revs.

Valve timing changes as well. You'd do well to degree your cam's now. If u search hard enough here or maybe the other boards, you'll find some interesting explanations as to why the timing changes.

...and, um... I'd only mill the head if it were NA (and had clearance) or warped: valve-piston clearance is a good thing.

 

[pinknuggit]

holy crap. I've never taken over .025" off of a 4g63 without junking the head. When I did mine, it was warped like a mofo and I only had to take .011" off the surface. When you got your head back, did the valves extend below the level of the head surface?

 

[Turbonium]

when i warped my head i musta doen a good job cuz he had to take 14/1000 off but i had no clearance issue's look in the haynes manual and it tells you minimium deck height for how much you can take off the head and if i remember correctly it was right around 30/1000 so i would def get another head just for clearances sake idk about a thicker head gasket, if u do get head studs as i'd imagine its harder to seal a thicker gasket.
Ryan

 

[AMS Eric #2]

I just got my head milled down 30/1000 of an inch and I was wondering if I needed a thicker head gasket than stock. Also what is the distance between the valves and the piston head at their closes point? 91 4G63T

Kyle,

.030 is waaaaaaay too much to be milling a head. You'll have clearance, timing, and head gasket problems with a head milled that much. Take it back to your machinest and tell him, congrats for destroying a good head. You at this point need to find another good casting, have it milled no more than .010, and have all your internals switched over to it. He should be doing this for free. He has machinest books that specificly state the service limit for that size head and he blatently disregarded it.

 

[imptuner]

with or without a jumped timing belt