If I take an L67 from a 98 Park Ave and put it in a 03 Bonneville, the procedure calls for swapping the oil pan and ALSO the harmonic balancer.

Swapping the balancer doesn't make sense to me. The physical shape looks identical, so there shouldn't be any serpentine belt compatiblity issue.

Can someone provide a meaningful reason why they are advising to swap the balancers? It seems that it would make sense to keep the one that came with the engine!

Thanks!

Is the bonne supercharged as well, or are you talking about swapping in a supercharged engine in a non supercharged car?

If the engine going in is a L67, then there is no real reason to change the harmonic balancer.

gtp2k2 - The Bonneville is supercharged as well. So this would be taking an L67 from a 98 Park Ave and putting it into an 03 SSEI.

Danthurs - If you check with any major salvage yard, the book/software calls for swapping the oil pan AND the balancer. I have to think there is a reason behind specifying this.

Any thoughts? Could it be due to transmission differences between the Buick and Pontiac platforms (but how would this influence the balancing needs)?

It'* not like swapping it is a big deal. Not sure what the difference would be.

I agree that it'* not a lot of work to swap the balancer (especially when the engine isn't in the car!).

I've had some bad luck with L67s in the past and I guess I'm being paranoid about understanding every step of the swap process. It seems counterintuitive to me to swap the balancers.

There is no good reason behind changing it. The job is to balance the engine with the flywheel spec'd for that motor. I've done a lot of these swaps and can verify it will not make any difference.

There is a slight difference in balancers based on the vehicle the motor was intended for. The GP guys frequently look for and put Bonneville balancers on their motors to smooth things out further. Some of the balancers are more refined for the luxury car super smooth running feeling. I'd think the PA and Bonneville would be the same balancer though.