Heavy bogging on take-off, caused by LFW?

[bflan2001]

My M42 swap is finally done, but I think I went too light on the flywheel. It runs great, idles OK, but if I don't rev it up before taking off the engine bogs like crazy. I went with the E21 M20 flywheel that weighed in at just over 12lbs. Should I swap it out for a standard M20 flywheel? Is there something else that might cause bogging like this? I've seen this issue before in another car and it ended up being the flywheel.

[Darky]

When you say rev it up? What do you mean?
What's your gearbox, diff ratio and which Bmw is it in?

[bflan2001]

I need to gas it up to at least 2k before I can think about letting the clutch out or it will fall flat on its face. And the faster I want to take off, the higher the revs need to be before letting the clutch out. I'm running the stock G240 tranny with a 3.64 diff at the moment, this is in an E21. I have a 3.91 diff, as well as a 4.40 gear set out of a Ti that I want to put into my E21 LSD. Do you think changing the diff would help? I thought I could get used to it, and I have somewhat, but it's still bothering me quite a bit.

[Darky]

Is it an early e36 g240? Or an e30 version.
3.64 is tall but should be fine, e30s had 4.1 but a lot of people put 3.73 in them.
With your light e21 3.91 would be the go.