Cracked head?

[85rturbo]

So ive been having several issues with my svo lately.
The latest is when i go into boost the car feels like it has very little power
Also i noticed that once it gets hot it will misfire a bit while holding the idle steady above 2500rpm but will rev perfectly smooth. Im on a pimpx set up and im pretty sure its not ecu related..compression was taken hot and cold.. cold im reading #1- 155 #2- 160 #3- 160 #4-160. Hot im reading about 10psi higher . Ive tripple checked my cam/crank timing to ensure i have not jumped a tooth or anything. Ignition is correct at 10deg and with the pip connected its reading what the pimp is showing on the dash..also i threw a new set of motorcraft copper plugs in it gap is .028 and the fuel pressure is set to 40psi dead head.. running 91octane and i have no vaccum leaks or exhaust leaks. I have swapped af sensors for known good sensors and my map is reading aprox 101kpa in california..im taking a long shot with the c acker head idea but i know its an issue with these engines but if anyone has any other ideas it would be greatly appreciated
Thanks

[Stinger]

What's the mileage on the head and springs?

By very little power are we talking like barely more than it makes before boost is built, or just not as fast as you think it should be? Do you have any "proof" of it's performance or lack thereof?

[85rturbo]

Aprox 1k miles on the head since it was assembled with all new valves, springs , retainers , guides and seals. Cylinder head and block were assembled together at the machine shop 2 years ago. I barley got the car running about a year ago but didn’t really drive it until about August-September ish. It’s definitely a noticeable difference. It does not feel like it has much more power than when its not in boost. Also i noticed even the bov sounds different when it goes off. At the time i was driving the car every day to work so i did notice the change in power. im reading 18psi of boost. If more evidence of my concern is needed please specify what type of info do i need? The best way to describe it would be like going into boost but you retard the life out of the timing.

[Stinger]

Were new hardened valve seats installed or were the stock seats just re-cut?

Did the problem exist since day one of the new engine or has it gotten worse over time?

Real evidence would be dyno or track numbers. We can diagnose without though.

[85rturbo]

Definitely was fine up until recently. Ran like a champ up until about a month ago. I dont have any dyno numbers. No harden seats. I believe that was a mistake on my part for not having the machine shop install them.

[Stinger]

If cam timing and ignition timing are for sure where they should be, I'd say the exhaust seats are leaking since they are no longer hardened. It's only a surface finish on stock heads so cutting the seats removes the stock hardening. A leakdown test should "prove" this theory, or you can just pull it and have hardened exhaust seats installed since you know it should be done either way.

[85rturbo]

Im thinking you might be correct. I highly doubt its a bottom end problem. I figure if the piston rings had a sealing issue it would not build any compression all the time. But my assumption is that 150+psi is a pretty good sign my problem is elsewhere like the head. The symptoms are more in line with like you said a crack in the head or maybe a burnt valve?

[Stinger]

Valve seats, not a crack or burnt valve.

When I had that problem 15+ years ago it was fine with a compression test but you could see light through the "closed" valve once I removed the head.