Originally posted by Keyser:
Crank case ventilation. Once I changed out that valve to one intended for boost it made a monumental difference.


It could be the PCV system but the stock PCV valve is more than sufficient to seal off the boost. If it is sealing normally and has the venting system setup correctly then there should be no smoke, or at least not visible to you in your rearview.
I'm inclined to think it's the rings. Stock pistons and rings will NOT blow smoke under WOT with the STOCK pcv valve unless they aren't sealing perfectly. I have not been convinced that the aftermarket pistons and rings being sold are actually sealing correctly as this isn't the first complaint or issue of smoke on the forged setup with aftermarket rings that I've heard of.
As far as the smoke issue, I had the exact same symptoms and I proved this to myself when I redid the pistons after blowing the first set. I honed the engine by hand and the rings never did seal up as tight as I liked though at first they were good. Over time the compression fell from being even to being 15% off in variation from cylinder to cylinder. Funny but they were all still in the standard according to the Ford cd but you know there were several cylinders that were not sealing as well as the others.
WHen I compression tested them it turned out that the low ones were the ones that were scored when the first sets of pistons broke. The only solution was a professional rehone and resize of pistons and rings.

That brings me back to the Forged pistons. THey design them with more clearance for expansion under heat. THe ring end gap is designed to be wider too. Under moderate conditions this will allow a lot of blow-by into the cyclinders even though there may have been nothing done wrong on the install. It seems to me that in our community here we will have to continue to research/test and adjust piston clearance and ring end-gap on this engine until such time as someone figures out the correct range of values that will work without having too much blow-by, noise but not fit too tightly as the pistons expand. Most of the clearances are being borrowed from other engines, especially the old school V8 crowd which I don't think are as relevant.
Back to stock pistons. The casting alloy and method used on the stock pistons causes them to have very little thermal expansion under higher temps. Consequently the clearance on the piston-walls is much tighter and the rings have a tighter gap. All of this minimizes blow-by and makes a quieter engine.

So there you have it. If he has stock pistons in that car then he is probably S.O.L. and needs to check compression. If he went forged then he needs to consider the other factors.

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black