I enjoy following this thread and keep wondering at what point the 4 main bearings in this engine would become a detrimental factor, with optimized head flow and increasing rpm, especially with a 12-port head ?
I read a while ago, from racers of these engines, back in the day, how they kept replacing the bearings all the time on these early inline 6s, built for all out racing.
Roadrunner -
My partner, Jerry Hall and I started racing GMC's in the 60's. Bearing problems have never been an issue. We are currently running two 302 powered dragsters. In the past 15 years we have incurred no rod bearing or main bearing problems (hundreds of runs)`.
We have run 7.79 at 170 mph with our 12 port car and 8.28 at 160 mph with our Kirby lump port head car in Denver at over 8,000 feet corrected altitude. The 12 port engine runs over 7,000 rpm consistently (sometimes with a little nitro). The only lower end change in over 45 years has been longer, lighter weight aluminum rods and a Fluid Dampner.
As Armond stated I feel harmonics is the biggest problem in any of these engines. We run stock main bearing caps with a support on the 2 centers and huge clearances - then and now.
My personal opinion is the connecting rods are the weakest part of the 261 engine. I feel with a good set of rods and a good balancer - the lower end will handle all the power you can make. Sometimes new technology isn't always better.
Bob
