I have a SBC400 (817) 2 bolt main cap and will like to get it splayed to be on the safe side of things. I have seen that most kits only contain the 3 middle Main Caps. Is that all thats required to prevent crank walk. The front cap and rear Main caps ($299) are very expensive, so is it neccessary to have all five Mains splayed or will the 3 middle Caps be enough to support around 450-500 hp/tq 95% street car. What is the majority of people doing when they get the block splayed. All five Mains or 3 middle Mains.
Thanks: David

 

most likely 2 bolt mains will serve your intended application just fine. if you feel the need to upgrade the 3 inner caps are all that's normally changed to 4 bolt.

 

Pretty hard to widen the 2 end ones without a totally different oil pan.

You don't even really need to do the 3 center ones at that low of a power level. You can get that out of a 400 with what would be little more than a good stock high-perf 350 build-up.

 

what does splayed mean?

sorry for the dumb question.

 

Normal 4 bolt pattern ---> ||.....||

Splayed 4 bolt pattern --> /|.....|\

See how the two outside bolts are angled out? That's what "splayed" means.

 

Here's a picture of splayed mains to give you a better idea.

 

what's the advantage?

 

Having two bolt holes that close together (stock or straight) weakens (sp?) the webing. By spreading the outside bolts away from the inside ones, you're digging into more meat, and keeping the holes farther away from one another.

You're also spreading the load over the exterior walls of the block, which are much more stable than the webing that goes across the mains. After all, that's the main purpose of using 4 bolt mains...... to stabalize the crankshaft and the bearings.

A lot of people think it's to keep the crankshaft in the block. I can tell you that if the crank decides to 'exit the building', not much is gonna stop it.

 

It requires more force to destroy it. Basically, but like my buddy CD said a second ago. If it wants to come out, it will find a way.