When replacing the head gasket?

all the machine shops around here are backed up at least a week or two, and i sort of dont have that kind of time. If it's absolutely crucial then ill make time, but if its not i might not have it milled.

opinions are appreciated.

 

IMO, its 99.9% required. You could do it without milling, but why risk it? Whats the point in putting in a new head gasket, ARP bolts and having a questionable seal when your all done?

 

Also, which gasket are you using? I'll put a plug in here for Cometic. Don't let the price disuade you--cheaper in this case is not crappier. Cometic makes an excellent product.

 

ill just be going with the OEM gasket.

 

Milling the head or deck is to give yourself a flat surface to mate against preventing future problems with headgaskets because uneven sealing/torque due to warpage.

Is it 100% necessary, no, but if the head has any form of warpage you will have inconsistent torque across the sealing surfaces and blow out another headgasket, especially between cylinders.

You can determine if you need it though by laying a straightedge across the gasket surface on the head (cleaned) and make sure there is absolutely NO space between the straightedge and the surface.. If there is, then you will need to mill the head to make it flat again.

Typically as engines "Season" (get used for awhile) their sealing surfaces warp or shift slightly and should be checked.

 

thanks jack, that was what i was thinking. I'll get a straight edge and check for flatness. Ive got 36k miles on my head right now, and im hoping i can just do the HG swap in one weekend IF i dont need to mill the head.

 

found the specs jack was talking about.

"3. Check the cylinder head gasket surface for flatness by using
a straight edge and feeler gauge.
Standard value: 0.05 mm (0.0020 inch)
Limit: 0.2 mm (0.008 inch)
4. If flatness exceeds the specified limit, grind the gasket
surface to specification.
Grinding limit: *0.2 mm (0.008 inch)
*Includes/combined with cylinder block grinding
Cylinder head height (Specification when new):
131.9 − 132.1 mm (5.193 − 5.201 inches)"

 

This really goes without asking...Its a MUST.

 

well not according to the mitsu specifications, I'll trust them.

 

why not go with an aftermarket gasket?

 

http://www.cometic.com/catalogs/AutoCat04.pdf

page 29

 

Are you doing the job yourself?

 

yes im doing the job myself.

I dont really want a stronger gasket. I think that you need a weak point in the engine assembly somewhere, and id rather have the head gasket blow out than have a rod break. The stock headgasket worked for 36k very hard miles, and im not racing near as much as i used to so im sure the stocker will last even longer.

 

Listen to what this man is saying.

 

Also worthy of note is the fact that should any machining be done to either the deck or head, the surface finish MUST be 50RA or better to guarantee a good seal with a metallic gasket. I saw a photo here recently of one decked block that was improperly done, so be advised.