Yes I remember that the US D jet pistons in a 4.5 are in the Hole like 3 mm I think, and the k jet Pistons are right up near deck height with a dished piston with quench ring. I did a bunch of research years ago. I wonder if the thinner head gasket could be contributing to the alloy blocks they are more prone to blow them. it'd be interesting to see the difference in thermal expansion between the iron block and the a390 silicon alloy block. I don't think the alloy heads are the silicon alloy correct?
I think my best bang for the buck is the 3.5 heads on the 4.5 to get the compression up. The euro 4.5 is rated at 222 horsepower and 278 foot pounds of torque with 8.8 to 1 compression and the US motor is 180 horsepower 220 foot pounds of torque with 8.0 to 1. The cams are different and no emissions garbage so actual difference in just compression who knows. Definitely will hit a Dyno before I pull this motor to swap if I get that far. I guess I would be put in the 5.6 Cams in it since the 3.5 cams in the heads are Rusty anyway. I'll be keeping my eyes out for a dirt cheap 4.2 just to get those heads to play with. They run the same cams as the 5.0 also so that's a win. Id like to get that head gasket, I'll pm you about that.
I just blew up the rear in the car yesterday anyway so I've got higher priority work including fixing my lift with parts I've been waiting 4 from Germany for 2 months, first set of Parts disappeared in New york April 8th. Second arrived yesterday. Got one side back together.
The rear was strange. I heard a loud noise that sounded more like a something striking the bottom of the car. After that any hard throttle would get a sliping and bad grindy sound. No noises under very light throttle or rolling. Limped it back to work went to leave and made 100 ft then no drive. Driveshaft spins with the rear tires on the ground. no leaks though. Oh well
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