You don't mention what plugs you were using, my experience with both the RS and V-5 is they like OD 289s turbo and standard. I run 60% with a .009 to .010 HC on both motors and rarely take out a plug. I also always pull the element out on the plugs which with my 67 motors is the difference between burning plugs or not. When using other brands of plugs, which I won't mention, plug life is not always good. In the last couple of years Ive learned that a balanced crank, a slight increase of the closing side of the drum or disk timing along with a thorough cleaning of the case and ports really makes a motor. My real real speed has come with Bouchie pipes, CMB nitro pipes and props from Mark and Brian Buass. I guess for me with CMB "stock really does work"
We've been running .008"-.010" clearance on our 45 engines, depending on weather. Like you, we like the OD 289's, but the last couple
of orders we've been getting 1-2 dead plugs from each order of 10- right out of the box. We've found the Rossi Std. and Turbo plugs to be
on par with OD, plus the Rossi's have much better selection for temp. range when going cold.
We haven't found a better pipe for the 45 engines than the NR #50901 (we drill stinger w/Z bit- .413") and we ceramic coat pipe and header,
and we run the pipe short and fat on 60%. Try one on your CMB's at 9.25"-9.5" and see what you think... I think the difference is in the
2 stage converging (baffle) cone.
For the money involved, that Bouchie pipe has nothing on NR nitro pipe with a full mod 46DD engine (we're running 193.8° Exh.).
These engines, either NR or CMB, really don't need any exotic trickery for a winning heat racer- just deburr, align things up, delay intake
closing 2°-3° and try to get as close to 28°-30° blow down as you can, without hogging on the exhaust port more than a couple of degrees.
I like those Steve Wood liner shims to test with on a day when the air is really good, too.
Thanks-
TW