Your options are to use the original Lucas item, which was a special rotor
with a sliding weight with springs. The faster it spins the further the
weight moves from the centre until it touches a grounding pin and cuts the
ignition. I've seen 6 cylinder bits set for 4500 rpm, and the commonest one
was the one that came stock in the Lotus Cortina - a 6500 rpm limit. You'd
have to adjust the weight to vary the limit. Problem is that the cost on
these is very high, and you might have a hard time finding one.
A modern electronic limiter such as the MSD that I use in one of my race cars
would be as cheap and probably more efficient.
I have to ask why you'd want to bother, though. With a stock MGB, you hit
valve bounce usually around 6200 rpm (earlier with old springs), and that
flattens out the power without valves hitting anything, thus acting as a rev
limiter.
I can't imagine needing a rev limiter unless you are running a tuned engine,
or a Twincam, which could easily be broken with right foot alone. Floor a
stock pushrod, it tops out and goes 'faugh'. Floor a Twincam, it goes
'zing-bang', the latter being right after it exceeds the valve bounce rpm
(about 7200 with stock springs) and the valves become friendly with the
pistons.
Bill
/// or try http://www.team.net/cgi-bin/majorcool
/// Archives at http://www.team.net/archive
|