[Jay S]

I have heard it is not unusual to find the spring roll pins in the lower hp 400’s too. I have never heard an explanation for it, I originally thought it was only the 77 W72 that only had the spring type dowel. Doesn’t appear to be completely the case. Could be when they brought back the heavier block for the w72 cars PMD had some carry over 557’s blocks with the springs pins that made their way to the lower performance 400’s. Either way there seems to be some other 557 400s that did not have solid dowels. If you do an internet search all the failed main webbing 557 pictures have dowels. It is hard to even find a good late 75 early-early 76 block (early production 557) that doesn’t have at least a small crack at the dowel, cracks even seem to show up on a 2 bbl 400s in that era.

Just my opinion, but with stock main bolts and either type of indexing pin, properly fitted, with a stock 3.75” crank and stock internals 350-400 HP is a good place to stop on the later blocks.

With ARP studs, which have much more clamping force, and proper dowels, preferably 5/16” dia to make sure alignment is true, and lighter 3.75 or 4” rotating assembly, I would go up to 500HP. No girdle needed. I think I could also make a pretty strong argument that the 4” stroke with the BBC RJ’s with the same heads, induction, ect is as good or better than the 3.75 rotating assemblies. The pistons on the 4” are a little lighter and shorter, roughly 25 grams, and the bigger cid holds the rpms back some.

The girdle I did is more designed to help the 4.21 and 4.25” combos for 450-600HP when used in the later blocks. I am not certain which is better yet for those combos, the solid dowels or the spring type. At least at first here, we are doing one of each. The girdle adds another level of indexing, especially when it bolts to the pan rails. An example of that is Ford Windsor’s do not have any cap indexing, they often use a Halo girdle to help index the mains more, and help control main cap fretting. The pan rail supports add another level to the control. Girdles are common on Olds and Buicks too. We do them on higher hp BB mopars, I have a pulling tractor with a full girdle and dry sump. They do make a difference for helping locate internal’s and limit the direction of the internal forces on the block. To a point anyway, once you get to a certain point on power things start to move again and it is back to square one.

The 557’s I have had apart so far have had a lot of nickel in the blocks, and seemed to be good iron. Maybe not quite as good as the early versions, but still pretty good. I just had a SBC thru here that I had to pin a hole where they ground thru and hit a water jacket, grinding on the bores for rod clearance making a stroker. Very soft iron in that SBC. I port quite a few heads, you can tell right away when they are short on nickel, the carbide burr eats thru it butter.