Rebuilding a 5.7 350

[jfrancom101]

So I am rebuilding a sbc 5.7, and this is a more general question but I figured some of you might know. I bought a rebuilt crankshaft which came with the resized bearings and while putting each one on I try to turn the crankshaft over by hand to make sure that it is still free moving. Well I got twp pistons installed and tightened down and there is more resistance due to the new rings, but once I put the third piston on the crank shaft is almost completely locked up. I tried loosening the bolts slight and it turned again but as soon as I tighten the bolts (not with a torque wrench but probably only 20 ibs pressure) the crank is locked up again. I tried pulling out the 3rd pistons and skipping to the 4th and the same thing happened. What could be causing that? I am using assembly lube the the first two installed rather nicely.
Though if I really push hard the crank will move a few degrees, it is a lot tighter than iv'e ever seen before and it seems to be just at the main bearing. Help?

 

[fast 99]

Yes, sounds like there is a problem.

If the crank turned free until the pistons were installed, mains are likely ok. Didn't say which bolts you loosened mains or rods? If the bearing clearances are too tight there might be some scuffing on them. Did you check the piston skirt clearance and ring gap?

If available, check the bearing clearances with plasti-gauge. It's not absolute, but a good indicator that there is or isn't an issue.

 

[fast 99]

Also, were the piston pins, skirts and rings lubed with engine oil?

Oil rings installed correctly? it's easy to overlap the expander.

 

[Bextreme04]

how did you verify clearances on the mains and rod bearings? Did you properly set the thrust bearing clearances? What were the main and rod clearances at for each one? Are you sure you are installing the pistons in the correct orientation?

 

[jfrancom101]

Yes, sounds like there is a problem.

If the crank turned free until the pistons were installed, mains are likely ok. Didn't say which bolts you loosened mains or rods? If the bearing clearances are too tight there might be some scuffing on them. Did you check the piston skirt clearance and ring gap?

If available, check the bearing clearances with plasti-gauge. It's not absolute, but a good indicator that there is or isn't an issue.

Sorry. so the main bearing for the crank seem fine, it was while installing the rod bearing that the 3rd one seemed to lockup the crankshaft. I haven't checked the measurements at all, but I am wondering the same thing if maybe the bearing are too tight.
I check the the ring gap on a couple of rings and they were good but I assumed that the rest were good also. I had the machine shop bore them out at 00.020 and I got that size of rings. Not sure what the piston skirt clearance is...they are new pistons and the first two installed very nicely. the 3rd and 4th locked up the crankshaft after tightening the rod bearings. if I loosen the rod bearing bolts to where they are loose again the crank turns freely again.

 

[jfrancom101]

Also, were the piston pins, skirts and rings lubed with engine oil?

Oil rings installed correctly? it's easy to overlap the expander.

I'm pretty sure I installed them right. my uncle who is a mechanic didn't notice anything off with them, and they still move up and down the cylinder so I don't think that it is the rings causing the issue. I did lube with oil as well

 

[jfrancom101]

how did you verify clearances on the mains and rod bearings? Did you properly set the thrust bearing clearances? What were the main and rod clearances at for each one? Are you sure you are installing the pistons in the correct orientation?

The orientation is correct, I haven't done anything to verify that the rod bearings are the correct clearance, but they are the ones that came with the rebuilt crankshaft so I assumed that they were good. How would I go about measuring that?

 

[fast 99]

Sounds like rods are too tight. Assume you're using Lubriplate or a lighter viscosity assembly lube. Not a thick lube of some sort like STP.

Get some plasti-gauge, check the clearances.

 

[Snoots]

You need a micrometer.

 

[Bextreme04]

The orientation is correct, I haven't done anything to verify that the rod bearings are the correct clearance, but they are the ones that came with the rebuilt crankshaft so I assumed that they were good. How would I go about measuring that?

Never assume when assembling an engine. Plastigage is a good cheap way to verify clearance. Something as small as a bit of dirt underneath a bearing shell can make it have 0 clearance. All kinds of things can be wrong in the machining, parts, or assembly. Best way to do clearances properly is to use a bore gauge and caliper to measure the diameter of the opening with bearing installed without the crank and also the diameter of the journal.

 

[jfrancom101]

Sounds like rods are too tight. Assume you're using Lubriplate or a lighter viscosity assembly lube. Not a thick lube of some sort like STP.

Get some plasti-gauge, check the clearances.

Yeah I'm using lubriplate. I'll get some plasti-lube tommorow. I've never used it but I'll try to figure it out.

 

[jfrancom101]

You need a micrometer.

Can I use a micrometer on the crankshaft? It won't scratch it?

 

[jfrancom101]

Never assume when assembling an engine. Plastigage is a good cheap way to verify clearance. Something as small as a bit of dirt underneath a bearing shell can make it have 0 clearance. All kinds of things can be wrong in the machining, parts, or assembly. Best way to do clearances properly is to use a bore gauge and caliper to measure the diameter of the opening with bearing installed without the crank and also the diameter of the journal.

Ok it would be good to measure that. Are those tools just at any automotive store? And have you seen a good video that explains how to do those measurements? Also what is the diameter of the journal?

 

[Salty Crusty]

Rods correctly oriented? Beveled side of the big end always goes away from the other rod, flat sides go together.

 

[80BrownK10]

Ok it would be good to measure that. Are those tools just at any automotive store? And have you seen a good video that explains how to do those measurements? Also what is the diameter of the journal?

A micrometer is same principal as calipers just more exact. I'm sure you can find hundreds of you tube videos useing them. I think you can buy them at Harbor Freight. Probably wouldn't use them as a professional or build race motors but for some checks your looking for they should do fine.