Rebuild in progress - can't turn crank?

[Praxiss454]

1965 GMC 1000, rebuilding the 230. Ended up actually needing a new block due to a crack. The new block is cast with a 1968 model year but looks identical.

I have the crank and cam installed. Main bearings torqued to spec (65 ft lbs). Sticky assembly lube on everything (because I don't know any better). I can't turn the crank by hand and I just wanted a sanity check on this before I go any further. Sound right? Bearings are .010 over, new-to-me crank is supposed to be freshly ground to the same by a reputable shop.

I tried putting bolts into the flywheel mounting holes on the crank and turning it with a screwdriver, to no avail. I recall when I was disassembling everything, I had a hard time turning the crank in this fashion as well, but it did move. Now it's not moving. I haven't tried my hardest but was worried about f-ing something up.

All the caps are in order and the arrows are pointing forward.

Tips/suggestions?

[Chevy Fleetside]

did you use plasti gauge to check clearance on the bearings?

[mongocanfly]

I wouldn't go any futher....tear it down and find what's binding..start by removing the center mains 1 at a time leaving the ones on the ends..check to see if it'll rotate by hand with each cap removal..

[Praxiss454]

Originally Posted by mongocanfly

I wouldn't go any futher....tear it down and find what's binding..start by removing the center mains 1 at a time leaving the ones on the ends..check to see if it'll rotate by hand with each cap removal..

Okay I undid the caps one by one and tested, and after I got cap #6 undone, it moved more freely. I re-seated the bearings, tapped w/ a brass punch tool to make sure they were square and flush, and reinstalled. The #3 cap was also giving me a little trouble so I did the same.

With everything torqued back to spec, I can't move the crank literally with my hand on a counterweight (well maybe I could with greater effort but not "easy" like my camshaft spins), but I can turn the crank by putting bolts into the holes where the flywheel connects and turning it with a screwdriver for a lever.

Does this sound right?

[kazoocruiser]

Originally Posted by Praxiss454

Okay I undid the caps one by one and tested, and after I got cap #6 undone, it moved more freely.
Does this sound right?

I don't know what kind of rear main seal you have, but loosening #6 might indicate that the seal, if it is a rope type two-piece is doing what it is supposed to be doing.

[Praxiss454]

Did not plastigauge it yet. How hard is it supposed to be to turn?

[jayoldschool]

Pretty easy. Something's wrong. Get the mic on it, and do a plastigauge check.

[Chevy Fleetside]

No.. You should be able to turn it with your hand. Need to check clearances. You might get some resistance but not that much.

[Praxiss454]

Originally Posted by Chevy Fleetside

No.. You should be able to turn it with your hand. Need to check clearances. You might get some resistance but not that much.

Okay I'll get some plasti gauge. But whats next if clearances are too tight? Drop another $60 on different bearings? Send my crank back to the shop and tell them **** doesn't fit?

[sirJim]

Originally Posted by Praxiss454

Okay I'll get some plasti gauge. But whats next if clearances are too tight? Drop another $60 on different bearings? Send my crank back to the shop and tell them **** doesn't fit?

Did you use oil on bearings?

[Rac65]

I know a guy that had this issue. In this case the machine shop turned all the journals except one so when he put the oversized bearings on it would not turn.

[1968k20]

Your block may need align honed. Talk to the shop that you took it too; they should be able to help you.

[jayoldschool]

To clarify... two of us have said to mic/mike the crank. If you don't know what that means, let's help. Get and use a micrometer to measure each of the crank journals.

https://mobiloil.com/en/article/car-...the-bottom-end

[Praxiss454]

Originally Posted by jayoldschool

To clarify... two of us have said to mic/mike the crank. If you don't know what that means, let's help. Get and use a micrometer to measure each of the crank journals.

https://mobiloil.com/en/article/car-...the-bottom-end

Yep I've used a micrometer before, I just don't own a good one. I have the cheapo digital caliper but I doubt it is accurate enough. Will see if I can borrow a mic from a buddy.

[mongocanfly]

Take it back to the machine shop...they'll have all the proper tools to find out what's going on...
It could be wrong bearings..crank turned wrong,bore line...or whatever...but you should be able to turn it by hand with minimal resistance....even if you had rods and pistons on it you should be able to hand spin it..

[Praxiss454]

The #2 cap and #6 cap, when torqued to spec (65 ft-lbs), cause me to not be able to turn the crank by hand. If I loosen these two, with everything else still torqued, it turns quite easily.

I plasti-gauged these two. As best I can tell, they are in spec, at 0.00125 (roughly halfway between .0015 and .001)

I guess this indicates that I need to have the shop check and possibly align-hone the block? Is there something else that could be going on?

[kazoocruiser]

Originally Posted by Praxiss454

The #2 cap and #6 cap, when torqued to spec (65 ft-lbs), cause me to not be able to turn the crank by hand. If I loosen these two, with everything else still torqued, it turns quite easily.

I plasti-gauged these two. As best I can tell, they are in spec, at 0.00125 (roughly halfway between .0015 and .001)

I guess this indicates that I need to have the shop check and possibly align-hone the block? Is there something else that could be going on?

Me thinks the crank got tipped over and bent. I could be wrong, and I am sure there are those who will come along and correct me if I am, but it seems more likely that the crank journals are travelling in an eccentric, than the block itself has loose and tight spots.

I've even heard stories of crankshafts getting warped by leaning them against something. They don't like it. Something about them turning up their nose at such rude treatment.

[Praxiss454]

Originally Posted by kazoocruiser

Me thinks the crank got tipped over and bent. I could be wrong, and I am sure there are those who will come along and correct me if I am, but it seems more likely that the crank journals are travelling in an eccentric, then the block itself has loose and tight spots.

It's a newly reconditioned crank (my last one was toast) from a specialty grinding shop that I believe just does cranks and things like that. So it would be shocking to me if it was not straight. And the ***** of it is, how the hell would I ever prove that I was not the one who bent it? I've been standing it on end the whole time it's been in my possession.

[kazoocruiser]

Originally Posted by Praxiss454

It's a newly reconditioned crank (my last one was toast) from a specialty grinding shop that I believe just does cranks and things like that. So it would be shocking to me if it was not straight. And the ***** of it is, how the hell would I ever prove that I was not the one who bent it? I've been standing it on end the whole time it's been in my possession.

It's all speculation right now. Someone is going to have to spin the crankshaft to verify there is or isn't any problems with it

[PGSigns]

The only way to fix this correctly is to measure everything. To check the crank you need a 1" to 2" mic for the rod journals and a 2"to 3" for the mains. Borrow mics with the .0001 scale on them. Measure all the journals size, out of round and taper. Write down all your measurements and make sure it is with in spec. Next you will need a dial bore gauge. Put on the main caps with out the bearings and torque them to spec. Check the bores for size and out of round and verify they are in spec. Now repeat the process with the bearings in. The difference between the crank measurements and the bearing measurements is your true clearance. With this information you can get to the true issue. They could range from a poor grind to miss marked bearings. I don't use plastigauge as it only tells you what you have and not why.
Jimmy

[kazoocruiser]

Originally Posted by PGSigns

The only way to fix this correctly is to measure everything. To check the crank you need a 1" to 2" mic for the rod journals and a 2"to 3" for the mains. Borrow mics with the .0001 scale on them. Measure all the journals size, out of round and taper. Write down all your measurements and make sure it is with in spec. Next you will need a dial bore gauge. Put on the main caps with out the bearings and torque them to spec. Check the bores for size and out of round and verify they are in spec. Now repeat the process with the bearings in. The difference between the crank measurements and the bearing measurements is your true clearance. With this information you can get to the true issue. They could range from a poor grind to miss marked bearings. I don't use plastigauge as it only tells you what you have and not why.
Jimmy

All of that is useful information, but only if the crankshaft doesn't have a warp in it. None of those measurements will pinpoint out of alignment main bearing journals. The crankshaft has to be tested on v-blocks or a lathe and measured for runout

[60-66]

.00125 to .0015 is not enough clearance. Should be .002-.0025. One thing I have to ask. When you put the main bearings in , did you put them in dry and super clean OR wet and oily against the block ?

[Praxiss454]

Originally Posted by 60-66

.00125 to .0015 is not enough clearance. Should be .002-.0025.

This contradicts what the GMC Maintenance Manual says for clearance, which shows 0.0003" - 0.0019".

One thing I have to ask. When you put the main bearings in , did you put them in dry and super clean OR wet and oily against the block?

There is a thin coating of 30 weight engine oil between the bearing and the block because I wiped the engine down to prevent rust. Maybe that is part of my problem. I also wiped assembly lube on the journals of the crank before installing. But if a thin coating of oil is enough to get the crank to not turn, I wouldn't think that is the extent of my problem. It seems like there is something else going on as well.

In any case, I dropped the block and crank off at the shop and they're going to take a look for me.

[60-66]

All bearings need to be put in dry during assembly, I always cleaned with lacquer thinner before putting them in. They will get oil behind them to prevent rust on there own , have never seen rust behind a bearing on a rebuilt good running engine so I wouldn't worry about that. Ive seen engines assembled that guys couldn't move the crank where oil was put on the block and back of bearing during assembly. We ALWAYS measured the bearings in the block like PGSIGNS outlined above, then ground the crank to fit .I was a crankshaft grinder for 20plus years. .0003 or three tenths on the low end is guaranteed to fail as they're showing in that manual , even .001 will fail eventually. I would be at the high end minimum for main clearance but as I've said I still "like" .002-.0025 IMHO . GM on an assembly line to gain clearance or reduce clearance had a wide range of over and under bearings even for a standard ground crankshaft. I can pretty much guarantee GM never assembled an engine with .0003 to .001 clearances

[60-66]

To the comment above on the "bent crank" yes that's a great thing to check and is very important. However , just knocking a crank over isn't going to bend it if it was perfectly straight out of the machine. Would take a pretty good hit to bend it.

One other area that will cause the crank to not rotate is the radius of the journal , if the bearing comes in contact with the radius it wont move , look for shinny spots on the edge of the bearing and also tap the crank back and forth before torqueing the thrust bearing. The tapping of the crank like that aligns the bearing to the thrust surface of the crankshaft. That's your "end play"