Originally Posted by slowman
i have never seen any big power gain yet and tried them on aleast 40-50 engines. when i do get a power gain it's never more the 5-10hp so i have to agree with topsportsman save your money and spend it some were else.
I tried one/for free as a test/when we dynoed My 572 BBC...fUNNY...just after I read the note of A PROMISED 15 TO 30 HP.gain I think the directions said,along with the gimmick "Bolt on,Sit down,and hang on,We fired the Dyno...It lost 10 hp.over no spacer...This was a 11/2 in.unit.....I then bolted on a Wilson open spacer and got the 10 plus 10 back.....'member though...it is all in the combination....