I have always heard people say on these idi fords that if you want good performance you need to shave the pistons so you can throw more boost into the engine withought causing the heads to blow. I have also heard you can double stack head gaskets along with head studs to obtain the same affect. Has anyone tried either and if so how did it turn out? I have a 6.9 thats getting a rebuild this week and im trying to figure out what to do. I have a banks wastgated turbo on the truck now.

 

i dont know about the double stacking but do know that the rest of the stuff is true

 

I am running milled pistons in mine 40 thou off the crown with Sealed Power standard 30 over pistons.

Dropped the compression ratio from 22.5 to 1 down to 20.25 to 1.

When I went over 22 PSI boost I blew the intake valley pan and exhaust manifold gaskets and had leaks in the exhaust pipes at every connection before the turbo.

So that took pulling the engine down again to replace the valley pan and exhaust manifold gaskets.
Also had to use studs in the exhaust manifolds and intake.
A search through NAPA's exhaust gasket bin and I found some gaskets I could use the the cross over pipe connections and the Y to passenger side manifold connections with a few modifications.
High temp Copper Gasket maker spray, triple coat both mating surfaces on the alley pan and exhaust manifold gaskets and the exhaust pipe gaskets.

When I installed the studs, I doubled the torque on both the intake and exhaust manifold bolts stock torque values.

I am also running ARP head studs torqued to 7.3 turbo specs.

In my opinion now I would have gone a different route.
Boost over 20 PSI from a single turbo is hard on the turbo if you spend much time above 20 PSI.
Also heat from the boost pressure becomes an issue on hot summer days.
So if I was going to run high boost over 20 PSI I would install a twin turbo setup with an intercooler and I believe 30 PSI would be about as far as I wanted to go even with everything listed above.
And I am not sure how well the intake and exhaust manifolds would do at 30 PSI.

If you use ARP head studs, have very true deck and head surfaces and keep all oil traces off the head gaskets and surfaces during installation I do believe I could have left the piston height stock if I kept the boost down to 20 PSI.
And even at 20 PSI, an intercooler would be a good investment if you want to realize the full potential of your engine work.

One thing to consider is how cold it gets where you are.
After I lowered the compression I find myself using glow plugs for the first start of the day even when it is 75 degrees outside, just to cut cranking time.
When it is cold outside, -10 F is as cold as I have stared the engine since I lowered the compression without being plugged in.
Yes it started, but I did have to give it after glow several times to keep it running for the first minute. (manual glow plugs)

So the bottom line here is how much extra work you want to get into besides the pistons.

 

I was planning on running at the max 20 psi. I was wondering what is the most effective way to get more boost out of the turbo?

 

Waste gate adjustment and more fuel combined with an open exhaust and better air intake path.