Cayman/997 engines

[blue72s]

Originally Posted by petevb

The GT3 cup motor is lighter than the GT3 street (no variocam, etc).

I didn't know about the variocam delete. Learn something new everyday. Anything else? For what reason they don't run variocam?


Another question: Which years Cup engine is the most liked?

[J P Stein]

Gee, Pete, you sure seem to know a lot about the GT3 electrics.

[petevb]

Originally Posted by blue72s

I didn't know about the variocam delete. Learn something new everyday. Anything else? For what reason they don't run variocam?


Another question: Which years Cup engine is the most liked?

Regarding the VarioCam, I think they drop it partly because they don't need low-end torque as much (they are close geared and spend time in mid-upper revs only), partly because they don't need a mild cam to help pass smog, and partly due to weight/ complexity. The 997 cup motors are listed ~15 hp down on their street counterparts because of this, though in reality, especially taking "area under the curve" into account, they are roughly as powerful.

In terms of the year, most people argue either for an early or late motor, with the mid years seemingly slightly less loved. Early ('00-'02, I think) ran lower 11.5:1 compression, solid lifter cams, and lower revs. Thus they are easier to run on pump gas, they generally have lower oil consumption, and time between rebuild *might* be longer. The middle motors switched to longer rods, different rod-end bearings and hyd. lifter cams; power and oil consumption went up- these are generally not as favored. The '05s-'07s had some small fixes, and power was uprated to 400. I believe they are also slightly lighter than the early motors, though compression and oil consumption are up slightly.

I understand that the '08 motor dropped the VRam style 2 chamber intake manifold and bumped compression up further to 12.5:1, and finally got a decent exhaust manifold. This should make it lighter still, and it's rated at 420 hp, so it's probably the one to have but it's expensive...
I'm told the '00-'02s generally dyno in the 335-340 rwhp range, while the late ~'06s dyno in the 365-370 rwhp range. Not sure what the '08s dyno at, but I'd guess ~385. All pre-'08 cars have a poor exhaust manifold design- ~20+ hp can be found by fitting a proper equal length manifold.

All of this info comes as word of mouth- I haven't found the big spec book that lists all of this stuff...

-Pete

[petevb]

Originally Posted by J P Stein

Gee, Pete, you sure seem to know a lot about the GT3 electrics.

Who, me? Just interested, is all...

[blue72s]

Originally Posted by petevb

The middle motors switched to longer rods, different rod-end bearings and hyd. lifter cams; power and oil consumption went up- these are generally not as favored.

Nothing wrong with longer rods (better rod angularity and piston dwell).

What was wrong with the rod bearings of the middle motors?
Could hydraulic lifter cams be reverted back to solid type?

and finally got a decent exhaust manifold.

~20+ hp can be found by fitting a proper equal length manifold.

Could this be retrofitted to pre-'08 engines?

[petevb]

What was wrong with the rod bearings of the middle motors?

No idea. Maybe they just were not improved enough to cope with the extra revs, maybe it's an oiling issue, maybe it's just a rumor...

Could hydraulic lifter cams be reverted back to solid type?

Maybe, but I doubt you'd want to. The lifters were carried over from the 959, I understand. What's often done at rebuild time is an update to a later motor spec. So you send in your '03 and say you want it built to '06 spec, spend a little extra money with the motor to PMNA and get the parts swapped out. It's not cheap, but having a PMNA rebuild is valuable in itself. PMNA keeps record of what's done, often provides an unwritten warranty, etc- mess with the motor yourself and the value is greatly reduced. Also if you mix and match by yourself you'll have trouble tuning. Most people outside of PMNA can't tune the bosch motorsports ecu, so the option there is to go Motec, etc...

Could this be retrofitted to pre-'08 engines?

Of course, and there are lots of other exhausts that make even more power at the cost of torque, etc. The early grand-am spec headers are cheaper and might be better depending on your application. I'd plan to swap the early cup headers and exhaust as a first priority- lots of power locked up there, and it's loud. You can also find a Grand Am spec single plenum intake (like the '08) and fit that, again at the cost of a little low-end.

If you want to go that far, however, you can just get an early grand-am spec motor and run it on good gas. The later ones had 2 ring pistons (vs 3 in the cup motors) that wear faster, but the early ones were quite similar to the cups. You can extend the TBO by cutting revs a little if you want. PM me if you want motors/ prices- I can point you to some.

-Pete