Rebuilding Engine - Need Help (1 Viewer)

[citric]

Howdy all!

I'm in the midst of my first engine rebuild. I got everything back from the machine shop and I have started reassembly.

I have the main bearings in. Crankshaft in. Main bearing covers in. I lightly coated the journals and the bearings as I put everything in. Without tightening the bearing covers, I can turn the crankshaft. It requires a little muscle, but it turns.

Specs call for the main bearing covers to be tightened to 90-108 ft-lbs. I figured I'd go middle of the road, so I set my torque wrench to 100 ft-lbs and tightened everything down. I tried turning the crankshaft and it didn't move. I loosened the bolts, except I couldn't get one of the bolts on the front cap to budge. I worked on it for 30 min with the impact wrench, but it would not move.

So I went ahead and tried tightening everything to 95 ft-lbs. Again, no crankshaft movement, so I backed them off again.

Finally, I tried going down to 90 ft-lbs. I checked movement with each cap I tightened. I tightened the front cap last, as it still had one bolt tightened to 100 ft-lbs. It still moved easily right up until the very end. Once I tightened the loose front cap bolt to 90 ft-lbs, it became difficult to turn the crankshaft. I can turn it, but it's not easy.

My question is two fold. How easily should the crankshaft turn in it's current state. Second, should I continue trying to break the bolt tightened to 100 ft-lbs, or let it be?

Thanks for any help!
brent

 

[ruger280]

I haven't rebuilt many, but my share, and my experience is that the crank will be tight when the caps are torqued down, but should be able to be turned. And the bolt... I'd let it be

 

[Buckwheat]

Which engine?

Refer to FSM for torque specs. Posted on this site, in many places. If you have a bolt you can't move, you need to get a friend and a cheater pipe on the end of your breaker bar to get it out. It is a very bad idea to proceed until you've resolved that issue. You may have installed the bearing wrong, or it moved & got smashed, so fix that first. You must remove all caps & inspect your crank journals. Did you measure everything yourself? Turn the crank or polish it? Align bore the block? Sometimes machine shops screw things up, so always verify their work. The crank is hard to turn even when done properly but it will turn, so there must be a problem & my guess is the cap where the bolt won't move. To assemble. remember to tighten down in increments, not all at once, because it actually bends the crank (minutely) if you have one tight cap & the rest are loose.

 

[Pin_Head]

The crank should turn easily with the main bearing caps torqued. You need to measure the bearing clearance first with plastigauge and make sure it is within specs. If you can't turn it with the bearing clearance in spec, then either the crank is warped or the block needs to be line bored or both.

You can't be off on any of these specs. Everything must be checked and verified to be 100% correct or it will be junk after you start it. If this is the first one you have done, it would be a good idea to get someone with experience to help you or have the machine shop do the assembly. You don't want to have a bad first experience and learn the hard way.

 

[Cdaniel]

Pin Head speaks the truth.
Check your bearing clearances.

Does this engine have any bearing caps with specific locations that may have been mixed up?

 

[poor boy pulling]

Pin Head speaks the truth.
Check your bearing clearances.

Does this engine have any bearing caps with specific locations that may have been mixed up?

No engine has universal bearing caps, each cap is bored to it's own spot, as well as make sure it wasn't but in backwards

 

[Cdaniel]

No engine has universal bearing caps, each cap is bored to it's own spot, as well as make sure it wasn't but in backwards

True.

I was getting at the possibility of something like a rear main cap being put elsewhere. Seems like that could cause a bind, if it's even possible. Mismatched other ones might spin okay but bite ya later when it runs.

Still don't know what engine is in question here. Chevy, Ford, Mopar, VW are my only experience.Never been in the gunnels of a Toyota I6

 

[RicardoJM]

Are you using the main bearing caps that belong to the block? As others have indicated, you should be able to turn the crank by hand with the main caps and bearings installed and torqued. In February, I helped a fellow club member rebuild a 2F and we were able to turn the crank over by hand with the mains installed.

In December I rebuilt my first F.5 engine and mistakenly swapped main caps between blocks. I noticed the issue at the same spot in the rebuild that you are at. I could not turn the crank by hand, but could turn it with a socket. I checked the oil clearance with plastiguage and it was within spec. The alignment difference was very small, but it does not take much of a difference to cause problems. In my case the engine seized and the #4 main bearing was toast within 60 miles. I was fortunate; cleaned up the #4 journal, rolled in new bearings and installed the correct caps. It could have been much worse.

As I understand it, the caps were installed on the block and then the hole for the crank was bored through the caps and block. The net of this is that caps and blocks are mated for life. Sure you can un-mate them, but like all mated for life situations things are much smoother is you keep them mated.

 

[RicardoJM]

Specs call for the main bearing covers to be tightened to 90-108 ft-lbs.

I don't have the FSM with me, but as I recall the torque specs for the #4 caps are different that for #1, #2 and #3. The orientation of #1 and #4 are hard to mess up. The orientation for #2 and #3 should have the arrow pointing to the front of the engine. The #3 is the cap with the bearing that has a shoulder. Another possibility is that you have the wrong size bearings. Did your machine shop measure and give you a recommendation and/or source the bearings?

 

[poor boy pulling]

True.

I was getting at the possibility of something like a rear main cap being put elsewhere. Seems like that could cause a bind, if it's even possible. Mismatched other ones might spin okay but bite ya later when it runs.

Still don't know what engine is in question here. Chevy, Ford, Mopar, VW are my only experience.Never been in the gunnels of a Toyota I6

i hear ya, IIRC 1 and 4 are really hard to mix up due to them having the seal surface on them but 2 and 3 can be switched and can turn with mild torque but when they get tight they bind as said above

 

[pb4ugo]

All good info. Also after tightening each cap check & make sure the crank still rotates. If you tighten all @ the same time you will not know which one is binding, if 1 is binding.
Don't forget to check crank endplay too.

 

[cea1]

Pin_Head is right on. You need to measure clearance with plastiguage. Something is not right if you cannot turn the crank fairly easily with the caps torqued down. You'll need to remove the stuck bolt and start over measuring clearance on each bearing. You're doing the right thing asking the question you did as you don't want to mess up installing the crank or you've just wasted a lot of money on a rebuild that you or someone else will be doing over again for you shortly.

 

[citric]

Thanks all!

I had been right on on all my other measurements, but I got this one wrong. I was able to get the bolt off with a breaker bar. I took the crank to the shop and it was in need of a turning. Should get it back tomorrow and the new bearings are on the way. I'll let you know if it all works out with the ground crank.

Thanks again!
brent