>The Datsun cam does in fact fit in an MGB engine -- Andy's got one in
>his race motor. Specifically, there are two improvements: the cam lobes
>are ground on a larger base circle, and the distributor drive gear is
>stronger on the cam than on the distributor drive shaft. The advantages
>here are that you can get a greater amount of lift out of a regrind on a
>Datsun core cam because there's more metal, meaning that if you grind to
>an MG base circle you end up with more lift between base circle and nose.
>To get the same lift on an MG cam you'd have to grind away too much of
>the metal and you'd end up with a weak cam. As for the distributor drive,
>the main advantage there is that on the Datsun cam, the driveshaft wears
>out before the camshaft gear, and you can lift it out and drop it in
>with little effort or expense. On the BMC cam, the cam gear wears out
>first, so you get to disassemble the engine to replace it.
Geez, Scott. Give away all my secrets, why don't ya. :-)
A couple notes: The larger base circle also doesn't wear your lifters
as fast. The the reason for less wear is the cut of the gear on the
camshaft, oil pump, and distributor shaft. What Scott said is
correct, but not because of the hardness of the metal. You *cannot*
mix and match BMC/aftermarket parts and Datsun/Nissan parts. If you
get a Datsun cam, you have to get the distributor and oil pump drive,
as well. It's pretty painless, though. An uncut camshaft billet is
about $60, the distributor drive $6, and the oil pump drive $5. This
is from your local Nissan dealer parts department.
The one "gotcha" of this setup is attaching the drive gear to the end.
Instead of the end of the shaft being threaded for a large nut, it's
drilled and tapped for a bolt. It uses a 3/8-20 bolt, just like
you'll find in your spare bolts drawer (although I'd recommend new
hardware). One of the thick manifold washers can be drilled out to
3/8" and holds the gear on beuatifully. Use Locktite.
And this arrangment sets you up for the second "gotcha." The head of
the bolt rubs on the inside of the timing chain cover. One advantage
to trying this first in the race engine is the fact that engine gets
torn down every 6-10 hours. It was only mildly disturbing to find
the bolt had almost worn it's way through the timing chain cover.
The next time(with a different timing chain cover), I dented the
cover out and the problem went away.
Have fun.
andy
banta@abingdon.sun.com
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