jrgordonsenior

Pics of the end of a GT3 Cup Car crankshaft after the flywhell sheared 3 bolts and rattled out the others. We originally thought the pressure plate/clutch had failed as it felt OK, just wouldn't go into gear. Check out the moonscape on the end of the crank from the flywheel rattling around. Unfortunately this will require a new crank and since we're in there.....

thusly

Sorry to hear; mind if I ask what the cost of a rebuild is? PMNA doing it?

tlark

you might as well.................

jrgordonsenior

Unknown until the motor's apart. Since it's an 02' motor, it will be upgraded to 03-05 specs which will add to the costs. It's being done by a local shop.....

cosmos

You know you will need to disclose the added HP of the 03-05' engines to race officals.

jrgordonsenior

Hey Cos,

Well after a season of racing my 04' with a fresh motor I can honestly state that they are all pretty evenly matched. No one was faster than me down the straight this year anywhere. I may have been a touch faster than a few, but most were dead even horse races. The PMS HP figures are subjective; a good launch off an apex will cure any minor discrepancy.

BTW, updates between model years are permitted....

99firehawk

sounds and looks like they rattled out then broke the last 3.

jrgordonsenior

Ah but what caused them to rattle out? The motor has roughtly 30 hours on it since a complete rebuild. Loc-tite was not present on the remaining bolts. So..... were the bolts not properly torqued on installation, or did the crank became harmonic for internal reasons and vibrate the bolts out shearing off those last 3. We'll see.....

jrgordonsenior

Split the cases today and found visible uneven wear on main bearings. I was also told today that a batch of 02' flywheels were unbalanced and replaced back in the day. That of course just adds to the list of possibilities.....

So possible causes are out of balance flywheel that vibrated loose, under torqued bolts on the flywheel though I don't belive that would cause uneven wear on the mains, a bent or unbalanced crankshaft, or most likely, a uneven line bore when the motor was rebuilt 30 hours ago.

So we may never know as the cases, being 02's, will be trashed and the motor rebuilt to 05' specs. Did you know that the motor parts for 03'-05's are cheaper than the early cup motor parts? Well me neither until today.....

gordo993

What are you going to do with that bad crankshaft?

JJayB

John,
The high rpm opperation of the Gt3 motor with on and off throttle applications create the stress on the flywheel bolts. I saw several similar crankshafts at PMS last year.

BTW, the 3.8 are over 500 hp. Who'd know.

Jimmy the fugitive (recently rehabilitated at traffic school)

993tt Andial 3.8 twin plug
A bunch of AMG's