1997 CVPI 4.6 Broken Crank

[gadget73]

Not sure how the 4.6 flexplate is put together, but on some motors the ring gear presses or welds on to the flexplate. It is possible for the ring gear to come off the flexplate on those. Its not common though. Stick a breaker bar on the front of the crank pulley and give it a spin. It should be fairly easy to determine if the crank broke. Honestly, it would be very very unusual to snap one without the crank pulley sitting messed up, or the starter making horrible sounds, or some other visual clue that catastrophe happened. Crankshafts are not easy to snap.

[p71towny]

Define "not rebuildable". Lots of people have rebuilt Modular engines, especially those with performance and racing goals in mind. Timing cover fitment is supposed to be a pain in the butt if head milling is required, though.

The clearances are such on those that you better know a DAMN fine machine shop to do the work. Hell, the rod caps are broke when they are made. Its funky.

[grandpaslincoln]

I'm starting to wonder if it was a good deal lol. A couple weeks after I bought that there was a '99 P71 that ran and the tranny was good and was in pretty good shape for $400 on Craigslist, the only thing wrongh with it was bad rearend.

Also, I do not believe the flexplate is broken because it is still in position perfectly like it's supposed to be. If it were broken, would it not be loose?

Since the flexplate is also bolted to the torque converter, and the converter is attached to the transmission, the flexplate will stay in position.

[bluebeast86]

Since the flexplate is also bolted to the torque converter, and the converter is attached to the transmission, the flexplate will stay in position.

Ah, I didn't think about that lol

[1987cp]

Hell, the rod caps are broke when they are made.

As in, they're cast in one piece and then split apart with a chisel so the caps only go back on one way?

[eaglegcil]

take the torque convertor cover off, and see if you can get it to slide towards the transmission, some of them will, if it does slide back then the flex plate is broken for sure. i'v seen that happen. you shouldn't be able to rock or slide the Torque convertor at all, if it seems to move independantly of the engine, then there's your problem. it's not really hard to change one either, a good weekend project. unbolt trans, slide it back enough to get the torque wrench back up there and your set.

[bluebeast86]

take the torque convertor cover off, and see if you can get it to slide towards the transmission, some of them will, if it does slide back then the flex plate is broken for sure. i'v seen that happen. you shouldn't be able to rock or slide the Torque convertor at all, if it seems to move independantly of the engine, then there's your problem. it's not really hard to change one either, a good weekend project. unbolt trans, slide it back enough to get the torque wrench back up there and your set.

Sure enough the flexplate is broken lol

[1987cp]

Nice to know the problem! Fixing is a bit of a pain but straightforward.

What breaks flexplates, anyway?

[Nathan in MI]

As in, they're cast in one piece and then split apart with a chisel so the caps only go back on one way?

Actually, what they do is cast the rod in one piece, and then freeze it (I think they use liquid nitrogen) so that it becomes extremely brittle. Then, they grab it at the big end where they want the cap to be, and just snap it right off. Advantages are that it provides a better fit than anything that can be machined, it prevents you from installing the cap backwards, and it prevents you from switching the caps between rods. The technology is known as "cracked rods" or "fractured rods". Pretty slick stuff.

[1987cp]

Man, that just sounds funky ... "fractured rods" ....

The '01 Saturn I helped rebuilt had the rods done the same way, and I'll admit it was kind of handy.

[grandpaslincoln]

Nice to know the problem! Fixing is a bit of a pain but straightforward.

What breaks flexplates, anyway?

Metal fatigue, probably caused by abuse. I can imagine someone doing neutral drops or something, would jar more than the transmission.

[bluebeast86]

Metal fatigue, probably caused by abuse. I can imagine someone doing neutral drops or something, would jar more than the transmission.

This thing was definitely abused lol the owners didnt pay the tow bill thats how i got it.