Flywheel HP vs road wheel HP

[Don Malling <dmallin@attglobal.net>]

I'm trying to get a rough comparison/understanding of the HP between my 
TR250 and MGB. The TR250 is still in pieces (restoration) and the MGB 
body shell has not been started.

The MG guys always speak of HP at the road wheels, and I think the TR 
guys always talk of HP at the flywheel. I think the stock TR250 had 104 
HP or so at the flywheel, and I expect I will have 140 HP or so at the 
flywheel when the engine rebuild is complete.

Is there a rough "rule of thumb" I can use to convert TR flywheel HP to 
road wheel HP?

Thanks,

Don Malling