[opeliac]

Originally Posted by mgarblik

As you know, the main bearing availability for Pontiac engines isn't great. We ran King and FM race bearings, just the regular stuff. Yes, we did have some cap walk, and yes I believe having cross bolted main caps would have helped. How could it not help? Clamping the main caps within the block structure makes the entire bottom end more rigid and able to withstand higher loads. ALL the really high HP racing engines have them. I guess the question is at what HP point do you really need them in a Pontiac engine. I would submit that the cast IA solid aluminum block needs them somewhere north of 3100-3300 HP. Would it have benefited us at the 3K HP we were making? Yes in my opinion. I did several things to help "crutch" what we had to work with. Bill Miller worked with me and shared several ideas I incorporated into our engine. You may know he ran BBC based engines in NHRA Top Fuel for several years. We used his special "peanut butter" lube on the studs and nuts and a different spray lube on the ends that went in the block. We torqued the main studs on to steel ball bearings dropped into the bolt holes. I cut the main caps which were steel, with an extra coarse dress on the stone, alternating the direction each cap faced in the grinder. This way the cap would lightly embed into the aluminum when clamped in addition to the register and the pins. All these little "tricks or band aids" did help. Made a noticeable difference. But there was still a little cap walk. Nothing that hurt the bearings, but it was there. That's all I can add from my experience. I love my Pontiacs, but a skirted block would be my choice.

How different do you think it would be if you were trying to make the same HP with a turbocharged alcohol combo?