For me, changing main caps is too expensive to put in a stock block. If stock main caps won't hold it I want an aftermarket block.
About 10 years ago there was quite a few 440's in my area that were breaking on the track, everyone of them had stock main caps. I noticed alot of guys racing every weekend with aluminum caps so I ran 2 different cars with low deck 400 blocks and aluminum main caps. There's alot of 9 second passes on those motors with zero problems. I'm a firm believer in the 400 block, ARP main studs, and aluminum caps.
Now that I don't race anymore I have a Duster with a 500" low deck pump gas motor, I bought a 440Source girdle and used stock caps. It works great but if I was gonna race I'd have bought aluminum caps. I read a few articles that said you really don't need aftermarket caps with a girdle. My engine builder did need the girdle to do the machine work on the motor.
