I also messed with the early 67 with only fair performance. I bought 4 for spares, and ran twins with custom built opposite facing Equi (Equalizer) 65 pipes on an Aeromarine Cat boat. I built the thing as a toy and a test bed for the new engines and entered the '88 IMPBA Top Gun twin event in Huntsville. My driver wanted one of the "Top Gun" hats they were giving if he made it to the finals. We stumbled into the finals, (using our emergency plan with stock 45's) so he was happy
. I found that the engine had lots of problems.
The compression was incredibly low for good performance, and even re-machining the chamber would not work, since the water jacket hit the block. I ended up re-machining Rossi 65 chambers which seemed best at .005 clr. The engine ran way too cold,so water restrictors were added. Next thing was the lousy carb, way too big, again Rossi 65 was used with adapters I machined. The engine balance was way off, and even with a lightened piston and "I" beaming the rod, it was still rough. :angry: I slugged the early style crank with 2 tungstons before the balance was even close. Then I squared the ports to see if the thing was air starved, no change. Finally I Packed the case with RTV to raise the primary compression and saw good promise. I scrapped the pipes and made new ones with longer midbands to lower the "kick-in" RPM which worked great. With the engines running correctly the boat was way too light since the CG was un-correctable for a race boat. If the engines staggered, as the pipes kicked in, the hull would vioently spin and roll, no way to put points on the board!!!(which prompted the use of 45's). It was a good thing I could buy wholesale since I owned a hobbyshop, I broke skegs on 9 sets of lower units which were machined for O-ring attachment to the engine. I later saw that K&B added a fillet at the factory to reduce skeg harmonics, which was far better than my Epoxy fillet.
So my personal advise for piped 67 O/B twins on a Cat boat, GOOD LUCK, YOU'LL NEED IT! :unsure: :unsure:
John in Huntsville