LLY - Cracked piston

DuramaxRamRod

Member
Oct 11, 2014
106
2
18
NH
Does anyone know the bolt for the 2020 oil coolers? Need the elbow bolt and the longer block bolts.
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,407
31
48
Boise, ID, USA
For what it is worth, the GM dealer sold me the following bolts, but I haven't installed it yet to verify:
  • Long bolt (have 2): 11588694
  • Medium bolt (have 3): 11515760
  • Different medium bolt (have 1, forget why): 11548821
  • Short bolt (have 3): 11548820
 

NevadaLLY

Adam B
Feb 24, 2019
186
7
18
Reno, NV
New measurements done. Followed instructions above exactly.
piston protrusion: front, back, average

Bank1
1: .0075, .0075, .0075
3: .0080, .0080, .0080
5: .0065, .0085, .0075
7: .0050; .0070, .0060

Bank2
2: .0095, .0095, .0095
4: .0100, .0090, .0095
6: .0095, .0085, .00875
8: .0080, .0065, .00725

Bank1: high = .0080, gasket A
Bank2: high = .0095, gasket A

Using head studs, if we assume squish to minimum gasket thickness, grade C will see .0394, or top of A gasket tolerance but 4 thou high. Since I’m on the low side of protrusion, I’d guess we need to see A.

New question...C will accept overbore. Will A or B?
My machinist says they took of -.005". Piston CH is down .010" so that means I've gained about .005" clearance. If I add the .005 to the max bank average above, it puts me right in tolerance for Grade C. With the block decked, combined with the CH reduction of the performance cast pistons, this is where my extra clearance came from and why my numbers didn't make sense before. Also, they now make perfect sense following the process as the book states. Once I can trade out my Grade C for Grade A, we'll be in good shape. On to VALVE clearances!
 

NevadaLLY

Adam B
Feb 24, 2019
186
7
18
Reno, NV
I may have missed a major step in the first parts of the rebuild... need input. I found that my machine shop didn’t re-install the main cap dowel pins for the thrust bearing main cap. Do I need to rip the oil pan off and the main cap and put those in? 🤦🏻‍♂️
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
2,400
115
63
Neenah, Wisconsin
Luckily you just need to remove the upper/lower oil pans. I use a dremel with a small wire wheel to clean the notches in the pan to remove all the silicone. You shouldn't have to remove any of the rod caps etc, should be able to just pop that cap off, put the dowels in, torque and go. Are you using OEM main hardware? I do know it is TTY so you'll have to replace that set of hardware (I'd imagine some guys reuse them but rather be safe).
 

NevadaLLY

Adam B
Feb 24, 2019
186
7
18
Reno, NV
Luckily you just need to remove the upper/lower oil pans. I use a dremel with a small wire wheel to clean the notches in the pan to remove all the silicone. You shouldn't have to remove any of the rod caps etc, should be able to just pop that cap off, put the dowels in, torque and go. Are you using OEM main hardware? I do know it is TTY so you'll have to replace that set of hardware (I'd imagine some guys reuse them but rather be safe).
Unfortunately, yes OEM hardware. I guess I'll need to get another set of main cap bolts. Do you know if I can source just the two bolts or should get another set?
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
2,400
115
63
Neenah, Wisconsin
Unfortunately, yes OEM hardware. I guess I'll need to get another set of main cap bolts. Do you know if I can source just the two bolts or should get another set?
They're sold in quantity 1, meaning one bolt, so you should be able to easily get what you're after from the local dealership/Rock Auto/online parts house.
 

NevadaLLY

Adam B
Feb 24, 2019
186
7
18
Reno, NV
They're sold in quantity 1, meaning one bolt, so you should be able to easily get what you're after from the local dealership/Rock Auto/online parts house.
Found them. Getting 2.

Anything else majorly simple I should look for when digging back into this thing? Definitely don't want to do it a third time.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,858
266
83
Phoenix Az
you might want to call your machine shop first. just because the dowels arent in there, doesnt mean they didnt do that on purpose (assuming they set the thrust clearance and put the crank in). i have seen cases where the factory dowels cause more harm than good when trying to get thrust alignment correct. i actually know of some very reputable places who will leave them out due to this.

that said, if you go through with it and new bolts, put a light coat of motor oil on the threads before putting them in. dont glob it on so you create a "hydrolock" situation and crack the block though.
 

NevadaLLY

Adam B
Feb 24, 2019
186
7
18
Reno, NV
you might want to call your machine shop first. just because the dowels arent in there, doesnt mean they didnt do that on purpose (assuming they set the thrust clearance and put the crank in). i have seen cases where the factory dowels cause more harm than good when trying to get thrust alignment correct. i actually know of some very reputable places who will leave them out due to this.

that said, if you go through with it and new bolts, put a light coat of motor oil on the threads before putting them in. dont glob it on so you create a "hydrolock" situation and crack the block though.
I set the crank in and did check clearance and all looked good but I'm not an expert builder - just being meticulous in my build process and checking everything two, three times over. All the other dowels were re-installed in the block. My fault for assuming these were too. My biggest concern is although the main cap is torqued down and tolerances were good, there could be some "walk" since the dowels aren't in place. Watching Guy's video on these dowel pins and the way to set/measure the thrust clearance really made me re-think that step and getting those back in.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,858
266
83
Phoenix Az
I set the crank in and did check clearance and all looked good but I'm not an expert builder - just being meticulous in my build process and checking everything two, three times over. All the other dowels were re-installed in the block. My fault for assuming these were too. My biggest concern is although the main cap is torqued down and tolerances were good, there could be some "walk" since the dowels aren't in place. Watching Guy's video on these dowel pins and the way to set/measure the thrust clearance really made me re-think that step and getting those back in.
in that case, follow his video and go that route. never a bad thing to go over it again.
 
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