I have a blue (heavier) crank, 2 mallory slugs still needed for internal. That's also with 2 rod throws drilled thru. If you're not adding stroke, maybe. I think Andy's red motor crank has 6-8 mallory slugs in throws.
Mart, You have a 350, Jim has the mains turned down .5" to 300 size. On Chris's 300 stroker with the heavier crank and 350 capscrew rods, no Mallory metal was needed.
I think more than anything else it depends on the weight of the rods, pistons, and wrist pins. I reduced the wrist pin size a bit and used thinwall pins. The stock parts are really heavy compared to good aftermarket stuff. Jim
Jim, what's the smallest pin size you feel is safe at 7k+ rpm with either boost or n/a h.p.? Finding very many custom pistons with small size pins available?
Probably more a wear issue than breakage, and of course as the pistons get lighter so can the pin. Those stock Buick pins are monsters. If you ever looked at the ones in motorcycles... well that could be an eye opener. And most of those are VERY durable. I'm presently using a .827" pin, pretty sure you can get down real close to 100 grams with those which is less than half a SBB pin. Every bit of weight you drop off the piston is a considerable advantage. On my 340 I used short .750" pins @ 72gr each but I think that's probably pushing it. It's never seen 7K yet, and I'm not really comfortable pushing it quite that hard, even though the pistons are about 450 gr each. Of course I'm not really all that comfortable pushing the Scat rods that hard either. They just look so dainty, you know? Oh, and just a tip, don't be tempted to use teflon buttons, they are WAY too heavy. Like 20 gr a pair. Generally you can get whatever pin size you want in a custom piston. But the key is to have the vendor work with you to get the pin weight you are looking for in the diameter you want to accommodate the ring package of choice. Generally speaking you have to go with whatever the rod has at the top end unless you are willing to bush them. Which isn't a bad idea with full floating pins but also isn't necessary with hardened ones. Sometimes a larger diameter pin with a thinner wall that is heat treated can be lighter and stronger than a smaller diameter. But I think something in the .800-.850" range is pretty safe. If you were wondering why I used the Scat rods, they were flathead Ford rods that used the SBB bearing shells and were very inexpensive and were 7" long. That let me use short pistons, reduce the weight and build a long rod motor. I really like the way that engine runs and I intend to keep it around for awhile. Eventually make some changes and bag it as a spare. It's slated for a roller cam, different head gaskets, touch up of the rear seal journal, and a new blower intake. For some obscure reason I like having spare engines around the place. Probably comes from a history of pushing them too hard. Jim
