2.9L Flywheel behind a 4.0L

[DPDISXR4Ti]

I've seen it mentioned a few times that it is highly recommended to keep the 4L flywheel behind the 4L engine when doing a swap from a 2.9. It seems the FM146 transmission is not up to the task nor is the 8.875" clutch. My plans are a little different however. I'm planning for a 4L swap into a 2.9 Merkur Scorpio, currently equipped with a T-9 5-speed. This setup uses a 9.5" clutch from the factory; the flywheel (weight) may or may not be different from the one behind the Ranger 2.9.

I'm not at all concerned about the T-9 being up to the task of handling the increased torque from the 4L. My concern is whether I might have any potential balance/harmonics issues with this combo. Any thoughts?

 

[adsm08]

You might be OK. 4.0 flywheel on a 2.9 is a common swap.

The issues with having a regular 2.9 flywheel on the 4.0 are all about the clutch not taking it well. The 4.0 can, under the right circumstances, smoke the 8 inch clutch without trying.

If the splines are the same I'd use the bigger 10 inch clutch and flywheel.

 

[DPDISXR4Ti]

If the splines are the same I'd use the bigger 10 inch clutch and flywheel.

Both the T-9 and M5R1 are 23-spline x 1" so that may actually be possible. I'd just need to put the flywheel on the rotary table and re-drill the flywheel for the bigger clutch.

Alternatively, I could use the Ranger flywheel, but only if that has the same ring gear count, O.D., and thickness.