I am rebuilding the 5.0 in my 95 GT. I sent the block and the crankshaft to simply be cleaned by a machine shop as they had no problems before and still looked good after disassembly. My problem is I got them back and started installing main bearings and after installing only one cap the crank is so tight I can barely turn it with a ratchet. I did plastigage the crank and it was around .001 which I am aware is incredibly tight. So I assumed that my new bearings were the problem. I went to the auto store bought standard bearings again and still too tight. Just to try it I reinstalled the old bearings and it still wouldnt turn. Now I'm incredibly confused becuase no changes were made to the crank or the block and now the old bearings are too tight to turn the crank.
Please help because it seems like the crankshaft has grown and that is the reason it wont turn. Obviously impossible......
No, after continued heat cycles over the years and constant stress on the block from hundreds of hours of engine rotation at various RPM, the casting will actually distort over time. As long as the top and bottom ends remains undisturbed, it's generally not an issue, but once the heads and rotating assembly is removed and the internal components aren't holding it in place any longer, the block can slightly "shift" out of alignment. Not by much, but enough in some cases to require an align bore to line the journals up again.
I can't see how just one main cap installed can make it tight. ??? Maybe 2 or more, but one?
Are you sure you have the correct cap in place, and oriented properly?
Could it not be seated properly? They often need to be seated with a dead-blow.
I have a feeling that if you torque it down before it is seated in the machined slot, it may distort or damage something.
What did you torque the cap to? I know that overtorque can cause what you are talking about.
Which cap was it that you installed?
Do you think you got the wrong crank back from the machine shop?
I don't know what happens when you mix a 2 pc main seal crank with a 1 pc main seal block, but I think that the 'rope seal' retaining lip around the back of the 2 pc crank will interfere with a 1 pc block. Someone else will have to confirm that, but I know you have to machine a 2 pc crank to fit a 1 pc block. If you accidentally got the wrong 302 crank back, that might explain it.
Had this happen on my Escort (first engine I ever rebuilt) back in 2000. We installed the crank backwards!!! Embarrassing, but always check the simple stuff first. Make sure you have the correct main caps in the right spots and torques correct like Ratio411 said. Otherwise, I would be going with Gearbanger and taking it back to the machine shop for a recheck.
Yes I used plenty of lube. Also, all the caps were numbered and direction lableled so they for sure were not installed incorrectly. I am very sure that all the bearings were seated correctly as well. Also, I torqued the caps to 70lbs in 3 different increments.
I think I have solved the problem by buying clevite bearings that allowed .001 extra oil bearing clearance. The crank turns smooth now.
I am building a 302 right now, and put new bearings, torqued to 70#, and I could spin the crank with my pinky.
If I stopped pushing the crank while a counterweight was up, it would continue to rotate even after I stopped pushing it until the weight was down.