I had this 2 bolt block that I snapped all 3 middle caps. (took it to school and block is not warped and everythnig is still straight on the bottom end)I also had a 4 bolt block laying outside that has a crack in the lifter gally up to the deck. Why not combine the 2? Well thats what I thought, and I went ahead with milling the block for the longer caps. The 4 bolt caps measure 6.2 right on the dot, and I take the block to 6.200. Everything is great, caps fit tight and the 2 bolts (havent drilled extra holes yet) screw down good. I was all giddy and excited untill I noticed the bore in the cap did not match the bore in the block... I turned the caps around and still did not line up, it's this way on all 3 caps.



In this picture RED repersents matrial removed, and the GREEN arrows point out how the caps do not fit. Judging by eye, I would say the caps are offset about .030. I was planning on having this block line bored and honed... But I am unsure if anything will clean up this big of a missalignment. Is it possible this will clean up? Or should I look for another solution? I know splayed caps are longer than 4 bolt, I could possibly re-machine my block and pay more attention to how the cap bores line up. Suggestions?

(please dont give me any heat about machining my own block, yes im young but i have made parts for boeing aeronautics. im qualified enough.  

I don't know of a way to fix this problem. We had this same issue with a 454 BBC last year and the "offset" created by the cap mismatch seized the crankshaft every time it was torqued down, and I don't think that difference was as large as .030"!  

Well I was thinking about making my own caps. And then possibly having them sent to beaver for heat treat. I will drill the holes first and then offset the main bore accordingly so they line up. Good idea. On summit the Mildon caps are made from ductile iron and the eagle caps are made from "steel billet". Anyone know what kind of steel? Or some sort of supperior steel?  

Well Im down at the shop and was tinkering... #1 and #5 caps are within .005 on the main bore. Cap #1 is a little loose though. Caps #2,3,and 4 are about .015 on the main. These 3 caps fit nice, and #5 is a little on the really tight side. Now that this is clarified, might this be cleaned up in any way? I have heard of people sanding the bottoms of the caps and then having the block align bored so more matrial can be taken off the caps. I could also mill about .0625 (1/16) off the bottom of the cap so the bores will deffinatly come out when align bored. Yes this will weaken the cap, but I could always modify the tops and make some straps out of some 01 tool steel... decisions, decisions...  

Sounds like a fun project, good luck with it. I'm just curious, just how much nitrous was being sprayed when you broke the main caps? Also, when you are doing this machine work in order to save this block, do you ever catch yourself singing "Here I come to save the day"?  

F-ing A! I'm Mighty Mouse! HAHA. Actualy I wasnt running any power adders, I just put alot of high rpm passes on my motor. When I pulled the block and had it on the stand, i was pulling caps and they just fell off... They didnt look cracked at all. They just fell apart when I loosend the bolts. I was mad. AND THEN I STARTED SINGIN'!