So I fitted the Lightened one that came with my motor and we had to do the runs on the dyno in 2nd
could not get above the cam to do tuning
real question is which is better and why I do know the general gist of it :
lighter : better acceleration and less weight (basically it)
OEM : might help with idle (it doesnt currently) and easier to hold speeds uphills/corners
keeping in mind application of mainly off-road/gravel and some track stuff (is addicting especially with slicks fitted
ask on oldschool, there are a number of race guys on there which will be able to tell you and have experience/knowledge to back it up
I run a very light flywheel in my race car. Works great for hill climbs but like yours it's idle is shocking and you really need to hammer it off the line, like drop the clutch at 4-5,000RPM or it will bog and stall. It is totally rubbish for road use.
What I run in the '75 is a slightly lightened Alpine flywheel, the Alpine flywheel is lighter than the OEM one and then I lightened it and balanced it a bit further. Nothing too extreme, idles well, holds speed perfectly at motorway speeds. It is a good middle ground between the 2 extremes which is what I built the engine as.
For what you are using it for and if you are going to be pulling big revs I would go for the light one.
Make the flywheel as light as possible.
The rough idling is probably down to getting the carbs balanced properly. There are lots of things that can affect it from the ignition system through carbs and exhaust, are the manofold gassets sealing correctly? and check the brake boister is not leaking?
My engine has close to double your hp and idles smoothly at about 1000-1200 rpm or jumps to about 1700 but not between. Driving on the road is fine once you get under way as there is little power at low revs so it needs a few revs and a bit of clutch slipping to pull away from the lights and the gears do need to be used. But as Avenga says, on an event you build up the revs and dump the clutch.
exhaust leek at manifold main culprit currently
but cheers for the fly down low!