Magic, Mirrors & Myths
MYTH - All headers make power.
FACT: Some engines are more respsonsive to headers than other engines. For example a TR8 reponds better to headers than a Triumph Spitfire or MGB.
FACT: Headers can/will make power in
different RPM ranges. For example , a 4 cylinder engine with a 4-into-1
header design will make power at the high rev range. While a tri-Y
design (4-2-1) will make power in the mid-rpm range. This is much more
useful on a street car since the majority of the drive time is probably
in the mid-rpm range. Another example of this is the stock cast
iron exhaust manifold on 1963 - '74 MGB's. This is a nicely curved
runner 2 outlet manifold that goes into a double exhaust pipe that
then necks down to a long single pipe. We tested some of these in the
early '70's and the stock manifold produced more power through about
4800 rpm than the factory competition department header. Once we
got over 4800 rpm, the race header started to perform, but, for a hot
street car, having power start at 4800 rpm is not necessarily the best