My torque wrench says it takes 80ftlbs (brakeaway, 60 constant) to rotate the crank pistons and rods. This seems very excessive to me, but this is only the 2nd engine (2nd Buick 350 as well) that I've fully rebuilt. No valvetrain is installed, just the crank, rods, and pistons. Stock bore, stock crank, stock rods, stock pistons, stock bearing sizes, Sealed Power Rings. They came pre gapped at .020, checked all 16 compression rings up and down each bore, measured at .019 to .020. Stock bore, stock rings, just ball honed. The crank could be rotated on it's own with my pinky, but after installing the pistons and rods it takes a ton of force to get it to move. There's oil in the bores (rings are sealing, none has leaked down), and moly graphite lube on all the bearings. Bearing clearance is roughly .00175 on the rods and the mains. All the rod caps come on and off effortlessly, but there is NO visible space between the rods themselves and the rods & crank throws. None. I did put a .004 feeler gauge inbetween each rod pair and torque them the 35ftlbs (TA spec for stud/nut rods) It is kinda cold here, was a high of 60 today, and that's 20 degrees more than what it's been for the past few weeks, during the night it's been below freezing. Could the metal have shrunk due to the cold? I built my '76 350 in May of 2016, and I didn't have this problem. Any input is appreciated.
I would say you likely have a rod cap on backwards or a rod in backwards. Take a close look to ensure the side of the rod with the angled chamfer goes against the crank counterweight...
Check your rod side play (feeler gauge between the rods) this will tell you if you have a cap on backward, or a rod in backward. For visual inspection on one you suspect simply remove the cap, and inspect the upper bearing half in relation to the crankshaft. The rod bearing is offset in the rod, and that offset is away from the crank cheek, and toward the other rod. Install the cap so the bearing is in the same relationship with the crank. 455's used a dot on the rod to indicate offset, not sure on the various 350 rods available if there is such a marking, but the 100% sure thing is to simply look at the bearing. I don' t keep turning torque specs here, simply because I believe that spec is nothing more than bench race triva. Sure, it's important to minmize that if your building an all out, who cares how long it lasts, race motor, but as far as I am concerned having the correct pre-lube on the bearings is much more important that being a star in the "turning torque" field.. And thick lubes will in fact affect that spec greatly. With those clearances, standard tension rings, with a high viscosity prelube, and your colder shop temps, it might be totally normal. But like I said, break out the feeler gauges, and check rod side clearance. I like no less than .008 ...more happy up in the .010 to .012 range on a stock rod mild rebuild.
Edit: Jims post came in while I was typing mine... good idea to use the feeler gauges. When you re assemble it is a good idea to give the crank a half turn after each rod and piston is put in to make sure it is not binding up.
Thanks for the input guys. I'll check the caps/rods and what not later today and report back if I screwed anything up. I did put a cap backwards on by mistake, and it wouldn't cinch down, that was the indicator for me. There is no binding of anything to speak of, and I am using that goopy moly engine assembly lube. I don't like the idea of using oils, as my engines end up sitting for a while before being installed. Hopefully it's just the cold weather, tight clearances, etc as Jim said if there's no assembly error.
Check for scratches in bore that indicate a folded over ring. Are these old Pistons? Did you oil piston pins at all? .
Remove the rear cap and see how much that changes. Seals all oiled? Always a good idea to give them a spin after installing each piston. Also a good idea to not put the rings in until everything is mocked up, without seals. Don't be hasty. If your pistons are coated, they are grabby if too dry or when any droplets of moisture are present.
Some of that moly lube can be really sticky and you have to be careful not to use too much of it because it can sometimes do more harm than good. A very light film is all you really want on the bearings and if you coat the cylinders with it I'd say it'd probably be best to wipe off as much of it as you can before the pistons go in. A little goes a long way. That may be all your problem is. It isn't grease. Jim
I agree it's for the cam lobes but I have seen it used on bearings and even on cylinder walls. Not the best idea but if it is a very thin film it'll be OK and could even help. But it's sticky in a place where the parts are running in shear so any build up at all is bad. I'm talking about a case where you rubbed it in and then wiped off all you could, leaving a very thin film. Regular engine oil would probably be better or for lengthy storage if you have access to some way oil (for machine tools) that would be a good choice because it is sticky but slippery and is made to allow parts to move in shear. If the OP smeared his cylinders with it that's very likely the problem. Jim
The 73 and later cap screw rods can only go one way and still work. The engine can still be assembled and rotated with rods in backwards, but it won't last long. I know. If you have one in backwards, that means you have another. If you look closely, you will see that they are offset. The earlier rods are not offset. (stud and nut type)
Moly in specially formulated oils have their place in the industrial world. It may not be compatible with the particular oil the OP uses and regarding bearings...could be corrosive to any copper in them.
Reporting back. Turns out, 5 and 6 caps were backwards, and 2 and 3 were swapped. All the rods and caps were stamped (assuming during P/O's rebuild), but they stamped 5 and 6 caps opposite the rods. I placed the numbers together instead of lock to lock. 2 and 3 rod caps were also swapped. The 2 was not as defined as the 3, so it looked like a 3. Plus, I was workin for 12 hours straight trying to get the car ready for thanksgiving. Stuff happens. Glad I figured it out now before anything stupid could've happened. Now takes a smooth 20ftlbs to rotate.
When you wiped the moly grease off to inspect your bearings, was there any damage from them not fitting the crank? Was everything fully torqued? I'm picturing some of them being wiped severely right now, having taken 80 lbs of breaker bar against them. It's great that you caught it, there's always time to do so before turning the key! That's when a mistake counts, other wise it's "mock-up and selective fitting"
