Subaru H6 - EZ30 Quench Height = .081" ???

[vristang]

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

Thanks,
jason

[vristang]

All my long winded ramblings aside...

Is .081" appropriate for the EZ30 H6 engine?



I did find a couple threads here, and I'm confident I can resolve all the issues that I mentioned.
I guess I would just like some confirmation that the .081" Quench Height is less than ideal, and I won't lodge a piston in the head by reducing the clearance to around .034 to .040 or so...

maybe no one has ever worked on these piles before

[PackardV8]

But it seems like the .081” is leaving some power/efficiency on the table?

Short answer - No, all is not as it seems. Subaru engineers aren't going to leave power/efficiency on the table unless going for it would compromise reliability.

Once in a while I pull a small trailer with it, and we make a couple long family trips a year in it.

Bottom line - don't screw with the family wagon. The wife will not be amused by your handiwork when a piston holes while climbing Wolf Creek Pass on July 4th.

jack vines

[nhrastocker]

But it seems like the .081” is leaving some power/efficiency on the table?

Short answer - No, all is not as it seems. Subaru engineers aren't going to leave power/efficiency on the table unless going for it would compromise reliability.

Once in a while I pull a small trailer with it, and we make a couple long family trips a year in it.

Bottom line - don't screw with the family wagon. The wife will not be amused by your handiwork when a piston holes while climbing Wolf Creek Pass on July 4th.

jack vines

Like Jack said, leave it alone.
Just use the new FelPro or Victor Reinz Multilayered (MLS) head gasket be done.
Do not use the OEM or other brands of head gasket. Also make sure you use new head bolts.

[vristang]

So, not trying to be argumentative, but every Subaru board I've been on says to ONLY use Subaru gaskets, and that the head bolts on this engine are not torque to yield and can be reused.
Is there something I'm missing?

After input here, and looking at the monetary cost, it isn't worth messing with at this time... But I may come back to it later...
Thanks for the input guys.

Jason