Quote:

how much horsepower or improvement in ET have you guys seen witching from the conventional collector to a merge collector



This might be a hard question to answer.. a TRUE merge
collector HAS to be designed for a certain engine..
but from the little bit I know about merge collectors
that COULD be as high as 25-30 hp.. again.. if designed
for that engine.. the diameter on the inlet, taper
rate and max diameter then the taper rate down to
exit diameter... its much like a 2 cycle expansion
camber... do it wrong and you move the power range
way down or way out of the rpm range... I played with
them on the dyno and finally gave up with what I was
playing with... so to just buy a merge collector off
the shelf is wasting your time and money... JMO