Good idea asking Cummins. The stroke from a regular 4BT is 4.72" and on the 4.5 it is 5.39". We are talking about 2/3 of an inch in increased stroke. I will also call my machine shop and see what they think.Good question. I see no reference to a repair sleeve on the specs for the engine block. In having been around shops that did that kind of work, the sleeve is normally a good bit longer than necessary. If I remember correctly, the 4.5 block deck is about 1/2" taller than the 3.9. Might drop Cummins an email inquiry and see what they say. Interesting that 3904166 from Cummins is around $120 and aftermarket replacements are around $20. Bit of price mark up there. LOL.
Could be that, or the fact that these are similar to the STORM blocks that have different threads for oil galleys and stuff. They are definitely an abberation. Even the naming convention...you say QSB and people lose their minds when you tell them there is an 8 Valve QSB in existence. When I get it back from the machine shop, I will take some measurements.Interesting, the push rods are the same so that would indicate the block height should be the same as a regular 4bt. However, the 4.5 block has the following part numbers 3938366, 4089546, and newest number 5406591. Those numbers do not appear on any other 4bt engine which tell me there's something different about those blocks. Could it be possible instead of raising the deck height they lowered the crank location. They could also have moved the pin location in the pistons. These engines are just weird.
Well, the torque numbers came out of an Army manual for the All Terrain Crane which had a 6bt. "B Series, Shop Manual, 1991 and 1994, Certification Levels". That might be the issue. Or part of it anyway. I only have the Owners Manual fro the QSB4.5 and QSB6.7 and that's not even for my engine nor does it have anything other than basic maintenance. I am going to delete it. These engines are as rare as hen's teeth so getting any info is not fun!Never heard of anyone having much issue with the crank cap bolts. Cummins doesn't recommend replacing those. Now the head bolts which are smaller are another animal. Are you sure of those torque numbers? A regular 4bt shows 44 lb ft, 66 lb ft, and then turn them 90 deg. However, there seems to be some discrepancy as to those numbers. Found another source that only shows a single step for a Cummins B series at 130 lb ft. Now the ISB and QSB engines show the multi step but I believe that is for the common rail block, not the style you have. Is that manual you have specifically for the QSB4.5-30 engine. The other QSB4.5 engines are a different block. You mention those bolts are 18mm. Was that the hex head size? According to Cummins they are M12x1.50x119mm Fracture Resistant Screw. Cummins part number 3927948.