The OPS .67 pipe works very well on a .45 eng, but you have to know if it is an older pipe with a .446 outlet i.d. or the newer version with a much larger outlet i.d. . The newer version needs to be choked down to .446 to give you the back pressure needed to pressurize the fuel system properly. If not then you will be chasing the needle all day long . It will run too lean and be very hard to get it on pipe , and when you do get it to come on pipe it will fall off very easily when you back off on the throttle and be very hard to get it to come back on since the eng is that much hotter and now the mixture has gotten leaner. Hope this helps. Geoff Overell.
