I am currently replacing the Head Gaskets in my 2001 Subaru Outback H6 – EZ30.
Once I took the heads off, I made the following measurements…
HG Thickness = .025”
Quench Pad is .045” below head deck
Piston is approximately .011” below block deck
Quench Height comes out to .081”
Does .081” seem excessive?
Is it worth the effort to reduce it?
I’m thinking that .035” - .045” Quench Height would be pretty close to ideal, without causing any contact issues?
If so, I would need to deck the heads.
The pistons would need fly-cutting for valve clearance. I don’t want to pull the short block apart at this point and I’m finding that MANY people have flycut pistons while still in the block with success.
The chambers (or piston dish?) would need to be enlarged to drop the CR back down to stock range of 10.7:1 (or maybe a touch higher?).
The cam timing would need to be corrected in the timing chain gears. There are no commercially available adjustable cam gears for this engine… that I can find anyway. So, I would need to have something custom made.
Can the required cam timing adjustment be calculated back from the thickness removed from the head?
I have a cheapo sonic tester... viewtopic.php?f=32&t=9656
And have measured the thinnest part of the piston top to be around .300" to .312"
The thinnest section I could find on the Head deck was about .300" as well.
I am a home garage tinkerer, and this car isn’t going to be used for any kind of extreme duty. Once in a while I pull a small trailer with it, and we make a couple long family trips a year in it.
But it seems like the .081” is leaving some power/efficiency on the table? Maybe it isn't an issue at all?
Is this a non-issue?
I did try searching here, but can't seem to find the right search terms to get anything meaningful.
The following link should take you to my photobucket album of all the pics I have of the engine while stripping it down...http://photobucket.com/SubaruH6-EZ30