So the short block was getting noticeably harder to turn as each piston was installed. The fully ***embled short block, including cam and timing chain should take no more than 40 ft lbs to start turning and about 20 ft lbs to keep it turning. Info straight from a 69 Chevy factory overhaul manual. And yeah, that means you should be able to turn it over and keep it turning with nothing more than a 3/8 ratchet. 40 ft lbs is a bit less than the rod bolt torque on a SBC, and 20 ft lbs is about the torque you'd put on a 5/16 hardware store quality bolt. Based on what the OP has said so far (not really enough info) I'd bet there's something wrong in the rotating ***embly. Until that's eliminated as a cause of the overall tightness, anything is just a guess. Piston clearance too tight? There's a difference in clearance depending on cast, hyper, or forged If the block was honed with a torque plate, were the pistons available to be measured to set the clearance for each individual piston? And were the pistons then marked as to which bore they are to be used in? OP says forged pistons, and if going to that expense then they should be bore matched rather than taking all bores to some size and hoping the clearance will be right. Rings gapped too tight? Were they checked in the bores prior to installation on the pistons? What was used as ***embly lube? Probably a hundred million engines have been put together using motor oil with no ill effects. No trick **** required other than for cam break in lube. Mismatched rods and caps? Guaranteed to make things tight. Pistons turned the proper direction? Did the crank turn freely with the mains torqued but no rods attached? Should turn with near zero effort. Lots of other possibilities, but these would be the most common causes of a tight short block.
Just a thought , Did you ***emble motor? did you use ***embly lub or just oil? Did you check rod and main clearance if so how. Same with ring gap piston to cylinder wall clearance . How did you adjust valves, are the lifters solid or hydraulic? Did you pre lube before cranking it over?
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