[mgarblik]

I was able to spend a few hours looking over and taking more detailed measurements on this SD-455 engine. I have decided to make some small changes in my plans. First thing I did was measure every piston very carefully. These are TRW +.030 factory replacement SD pistons. To my surprise, they were very poorly finished for size. The skirt measurements at the tip varied by .004" through the set!! That's pretty bad, IMO and although pistons are definitely more accurate today, I don't remember them being that bad in general 30 years ago. Under the oil ring measurements vary by .002" through the set. Skirt taper varies from one piston with a negative taper of .0005", to an average taper of .002" on the other 7 which is OK. Overall, pretty disappointed in the quality of the pistons, although they look fine visually. That's why you have to measure everything. So my new plan is to re-hone the block and select fit each piston to a cylinder and set the correct .006" piston to wall clearance. Fortunately, they are all too tight now around .002", so it's just a matter of finish honing. The line hone is similar. Too tight. The housing bores are .0005'-.0007' tighter than I like them. I put them right on spec. and these are slightly tighter than tolerance. My understanding is this was typical 30 years ago as shops were concerned about spinning bearings in large main size performance engines. But since I have to hone the cylinders anyway, I might as well fix the line hone as well. Finally, after some careful thought, I have decided to change out the rod bolts. ARP makes rod bolts specifically for SD-455 rods. The head design is a little different. I hope the weight is similar. Will have to weigh them and see. I am concerned with stretching the original bolts 3 more times. once to measure the rod housings, again to dial bore gauge the oil clearance, and a third time for final assembly. Just too many cycles as these bolts may be original and I don't know how many cycles they already have on them. So a little work ahead to make sure everything is as good as I can get it.