[rpol78]

I am using the LS9 specs which are .0008 - .0021 for production and .0008 - .0025 for service. My understanding is the tight bearing clearance spreads the bearing load better than a looser clearance and the aluminum block expands more at operating temperature which again increases the clearance. Also the Calico bearings are coated bearings which result in tighter clearances and some of the coating will wear during break in resulting in more clearance. Either way the key is to run the correct oil viscosity for the clearance.

FWIW - the rod spec is .0009 - .0025 for production and .0009 - .003 for service.

I'm not a professional engine builder so maybe one of the experts will chime in.

 

[07GTS]

yes u will have to go a thin oil, from my build and research (im not a pro either) its can be good to have some looser clearance for boosted engines as the crank can flex and also the more oil u can flow thru it the cooler the bearing will be, u do have a good solid crank tho so flex should be minimal (im using the dragonslayer in mine) i watched the steve morris LS free build and he puts some good into in there, yours will be a tuff engine tho will make some good power should be fun once done

 

[rpol78]

On the crank flex, the LS9 block does have the pinned billet main caps which should help also. My original goal was 900 crank hp on 93 octane. We'll see if I get there.

 

[rpol78]

I ordered a set of .001 undersized main bearings. Oddly the crank has a tight spot that begins to show up at around 45 ft lbs of torque. At 60 ft lbs on the inner studs it feels about the same as it does at 45 ft lbs. If I have momentum it moves right past the spot but if I stop there you can definitely tell something is not right. I would think if the mains were out of round or the crank was slightly bent I'd get two tight spots 180* apart but that's not the case. Looking at the main bearings they aren't showing any wear but they do have the Calico coating on them.

Anyone seen this before?

 

[random84]

I ordered a set of .001 undersized main bearings. Oddly the crank has a tight spot that begins to show up at around 45 ft lbs of torque. At 60 ft lbs on the inner studs it feels about the same as it does at 45 ft lbs. If I have momentum it moves right past the spot but if I stop there you can definitely tell something is not right. I would think if the mains were out of round or the crank was slightly bent I'd get two tight spots 180* apart but that's not the case. Looking at the main bearings they aren't showing any wear but they do have the Calico coating on them.

Anyone seen this before?

Seems like it would be a variance between one "end" of the crank journal being slightly over, and either the main or the cap also being slightly out of round so they both increase resistance in only one spot per rotation (but are increasingly loose on the 180* side)? Or, the crank itself is not perfectly true within the main journals.

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[MeanMike]

To have one tight spot in the bearings you’d have to have an out of round crank journal and and a some thicknesses variation in the bearings on the same journal. Both are possible but unlikely together especially on a good us made billet crank.

What about a counterweight hitting somewhere on the block? I assume this crank is center counterweighted, look around them.

 

[MrSurly]

Assuming just the bare
crank installed?
Check the thrust faces.

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[rpol78]

To have one tight spot in the bearings you’d have to have an out of round crank journal and and a some thicknesses variation in the bearings on the same journal. Both are possible but unlikely together especially on a good us made billet crank.

What about a counterweight hitting somewhere on the block? I assume this crank is center counterweighted, look around them.

Yes on the center counter weight crank. I'll look at it closer but the counter weights look like they're clearing. I'm a little concerned about the reluctor wheel. It looks pretty tight.

Assuming just the bare
crank installed?
Check the thrust faces.

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Yes just the bare crank. In checking the thrust I'm measuring .005 which is consistent until I get to about 45 ft lbs. Then in the one spot the crank won't move forward or back since it's tight. That leads me to believe that maybe it is contacting the block some where. The reluctor wheel seems suspect. I checked the runout on it and it's about .012 which is within the spec (i.e. spec.028).

 

[rpol78]

I can't see any where that the crank is touching the block. In working with it I was able to rotate the crank a few times slowly with really no resistance and then it would seem to hit the tight spot. The tight spot is always in the same place in the rotation.

It seems like the crank has to be touching block somewhere when it's all of the way forward or back.

 

[MrSurly]

I’m sure you done it over and again, but I would probably pull the crank and each bearing shell and make certain there is nothing between the shells and the block or the caps, not even a bunch of oil or assembly lube.
We’re clearly grabbing at straws, here.

 

[jcs003]

Take it to a machine shop, a higher level of inspection is needed.

 

[rpol78]

I’m sure you done it over and again, but I would probably pull the crank and each bearing shell and make certain there is nothing between the shells and the block or the caps, not even a bunch of oil or assembly lube.
We’re clearly grabbing at straws, here.

At first I thought it was the Driven Assembly Gel building up so I took the crank out and cleaned the saddles, caps, crank journals, and both sides of the bearings. I then put it back together with 10-40 oil on the crank side of the bearing surfaces. I'll keep looking today to see if's touching somewhere.

The challenge is if it is touching it's so lightly that so far I'm not seeing any witness marks. Maybe I'll try putting a light coat of ARP assembly lube on areas that are suspect for touching to see if something shows up.

Take it to a machine shop, a higher level of inspection is needed.

.
I'm not sure who I'd take it to in Kansas City. I do have micrometers, a bore gauge, vernier calipers, etc to measure with. It take a little thinking with everything being aluminum to find a place to mount the magnetic base for the dial indicator. I've built several small blocks and big blocks and never had an issue like this. Admittedly the bearing clearances were greater than the LS9 spec calls for.[/QUOTE]

 

[MeanMike]

Did you have any machine work done to the block, or is it as delivered from GM. A few posts back you mentioned main studs. If you didn't have it line honed, the mains are probably out of round.

If you want to check the crank, put the front and rear main bearings in the block and leave the middle 3 out. Put the crank in and set on indicator on each of the 3 main journals on the crank and check them for runout.

 

[wawazat]

Did you have any machine work done to the block, or is it as delivered from GM. A few posts back you mentioned main studs. If you didn't have it line honed, the mains are probably out of round.

That is the first thing that came to mind for me. We had to send my LSX block back to the machine shop (next door to the builder) because we forgot to specify line honing after installing the main studs. The crank definitely didnt spin smoothly until that was done.

 

[MrSurly]

I'm going with line honing for the win.

 

[rpol78]

That is the first thing that came to mind for me. We had to send my LSX block back to the machine shop (next door to the builder) because we forgot to specify line honing after installing the main studs. The crank definitely didnt spin smoothly until that was done.

When you say it didn't spin smoothly what exactly was it doing?

This one is odd because it will spin freely for 3-5 rotations and then it will get tight in the same spot each time. I'm picking up a little noise toward the rear of the block so I think I'll pull the crank to see if I see anything.

I have the main bolts and could reinstall them to see if it makes a difference.

 

[wawazat]

Mine just felt tight. It would spin but definitely not freely like it should with just the bare crank installed.

Spinning freely for multiple rotations then binding makes me think something is slowly shifting with each rotation until it has moved enough to cause interference or excessive friction.

 

[rpol78]

I know the bearing clearances are a lot tighter on this (i.e. .001 - .0015) than I've used on small blocks and big block chevys in the past. I've got the .001 undersized bearing set ordered so I'm thinking of either going up .0005 or .001. Maybe targeting .002 clearance would be a good thing. That's at the upper end of the GM LS9 spec (.0008 - .0021)

I may have another go at checking the main bearing saddles to check for an out of round condition. My challenge is my bore dial gauge is only good for .0005, which was fine for SBC and BBC, so I may need to invest in a more accurate one.

 

[MrSurly]

The confusion caused by "turns free several revs and then binds" is likely simply due to the crank moving ever-so-slightly front- or rear- ward while turning.
Set up the dial indicator and you'll likely find the bind related to f/r position.

 

[rpol78]

I pulled the crank an measured the saddles and it does look like they're out of round. Now I need to find a good machine shop. I'm in Kansas City, any recommendations