I started putting my engine together again (damn clearance problems) last weekend and after I got the first four pistons in, I can't turn the crank anymore. I've been turning it by hand on using the counterweights....it won't budge now even if I hit the counterweights with a rubber mallet. I'm going to get a crank socket, but if I can't even get them to budge with a rubber mallet, it just seems like something is wrong. How can I tell if the pistons are on the right rods? Any other suggestions? This is my first engine buildup, so it could be normal and I just don't know.

 

This is just a shot in the dark here but did you gap the rings yourself and/or check their gap before driving the piston home? Did you purchase the correct bearing oversize if you had the crank machined? I dont know...just a thought.

 

usually the crank it's self will spin freely, but when you add a rod and piston you need a crank socket. make sure your end gap is correct, the bearings are correct size, you don't have pistons in backwards. another problem area is the oil pump bolt/stud can interfer with the bearing and bind the crank.

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-=ICON MOTORSPORTS=-

 

I noticed that when I did my first engine a few years ago. (Actually the only engine to date) Everything was correct, there was just too much friction to overcome as more pistons went in.

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90 TBI 305 Formula
Original Owner
Auto Trans, T-Tops
Completely Stock Except:
--Flow Cooler water pump
--180 T-stat

 

If you are worried about putting in the rod/piston combo in backwards, then look at the big end of the rod. Looking directly from the side of the rod, there are two different sides. One side sticks out more than the other. The side that sticks out more always goes toward the crankshaft edge (fillet side), left or right doesn't matter, as long as away from the center of the crank throw. The narrow side always butts up against the other rod on that particular crank throw (which also has its narrow side pointing back). Problems can crop up here if you have domed piston that are installed on the rods incorrectly. And to some point, valve reliefs on the top of the pistons can be in the wrong place if the rod is not installed correctly. When you start putting piston/rod combos in, the amount of force required to turn the crank gets higher. By the time you get them all properly in, you SHOULD have to use some kind of leverage, the best would be a crank snout socket. If you are worried about piston ring gap, place a loose ring in the cylinder, square it up in the cylinder and measure the gap. Specs for that particular ring should be in the installation instructions or use a shop manual. If the gaps are too small (which will cause major problems if not corrected), they can be gapped by file fitting each one. Takes some time but worth the effort on most engines.
jms

 

The gaps on the rings should be ok...I checked them myself before installing them on the pistons. I definately will check to make sure the machinist put the pistons on the correct rods. Other than that I know I have the right bearings and the crank did spin freely before I installed any pistons so maybe it's normal and I'm just not used to it.