So I will give some details to the last couple months.
Back in February I noticed some white smoke at idle when cold, this problem slowly got worse, I babied the car back and forth to work for 2-3 months. I figured it was either a crack in one of the ports or the head gasket. I figured I would try swapping in studs if the bolts weren't cutting it, thanks to TDISyncro for the research and info. I got the stud's here and realized the stud nut interferes with the cam caps on a PD. Had my machinist turn the nuts dow to fit properly. During this time I also had ryanp send me 2 PD130/150 heads, one core and one that was taken off a running car. Sent the core to the machinist and cleaned up the good one.
With everything ready to go for either situation, I tore the head off. The head gasket looked perfect, no signs of coolant loss. So the PD150 head bolts were holding my power levels just fine.
A flashlight in the port showed traces of coolant crust in 1 exhaust and 1 intake port. This head had 22k miles on it when it started to fail. I figure this happened from thermal stress on an aggressively ported head.
So plan 2 starts. Swap all my parts onto the new to me head and put the car back together with the new ARP studs torqued to 105'#s. I would have run PD150 bolts again without hesitation, except I had already paid for the studs and machining. Plus I will be doing another head swap and can reuse my studs.
All back together and driving fine. The butt dyno was telling me there was a little tiny bit less top end.
The real dyno confirmed this as well. I hit two different shops with the same model dyno and came up with matching numbers.
Here is what I turned at a dyno day with no fan.
I couldn't believe the torque loss. HP was on target with my feelings but the TQ seemed wicked low since my lowest TQ with ported head and PD150 injectors got me 388wtq.
I discounted this run as inaccurate since it was not on my standard dyno.
Today I went in and made passes on my normal dyno with my normal operator.
Same tune and what not from previous runs only difference is timing was -1.0 today vs. the previous with timing at +0.5
And of course this is with a stock head
I also hit the drag strip this last weekend and pulled a 14.5@100mph on my street tires. This was pretty much an identical run to my last one with the ported head and street tires at TDIFest. It wasn't noticeable at the track since I am only down a couple HP in the upper rpm range.
Right now I am working on getting a new set of pistons machined up so I can run my new big valve PD head. I am hoping to be done with the bottom end and head swap by August so I can get my numbers and continue with injector testing and be all done with this thing before August 20th for a big NHRDA event here in town.
O.C.
quite alot of boost at 2000rpm =)
