I have learned some expensive lessons lately, and thought it would be nice to pass them along so that you may not make the same mistakes I have.
Stage 2, 07 STI broken ring lands.
Over the winter from 2010 to 2011 I installed new Mahle pistons. To do it properly I split the block so that the cylinders could be honed to clean them up. New rod and main bearing were installed just because I was there. Engine ran great and didn’t leak at all. A 20G turbo was installed and the tune was done in April/May. I was daily driving just for the fun of it. It was done and life was good.
4 days before my first track day of the year..............
I spun #3 rod bearing on my newly rebuilt engine. At first I blamed Cobbs Flat Foot Shifting as the problem started right after it engaged. http://www.iwsti.com/forums/ecu-tun...-electronics/218716-can-cobbs-ff-shifting-cause-engine-damage-when-not-use.html After more research I have concluded that there were 2 issues and both centered around my poor assembly and the sealer I used. Cobbs FFS was just the straw that broke the camels back.
In all reality there is a short list of things that can cause a spun rod bearing.
Lack of oil
Poor bearing clearance (to big or small)
Improper assembly
Poor bearing construction
Detonation.
Subarus have a poor reputation when it comes to rod bearings. It is why the oil pumps have gotten larger and the crank shafts have been nitrated.
I have read a lot on checking bearing clearances. Let me let you in on a little trick I learned when I was learning how to rebuild diesel truck engines. If its not broke don’t fix it. The bearings and wear looked fantastic, so why go through all the time and trouble checking it all. Stock crank, block, and bearings is what I had and it was in great shape. I just replaced like for like. In other words bearing clearance was not the problem....... sort of.
Poor bearing construction; I spent $380 for a nice shiny OEM set. Definitely not the problem.
Improper assembly; Assembly was checked and rechecked many, many times as I was meticulous with the reassembly. Besides I flogged the engine for 300 miles before it started knocking.
Detonation; Absolutely no sign of it at all. Tune was very conservative and the logs had no knock. Pistons looked great except for all the bearing material embedded in the coating.
Lack of oil; When changing the oil just before the spun bearing I did notice metal flakes in the oil pan. Not good, but it was the first oil change after rebuild. Examining the block after splitting it in half I noticed a BB sized piece of sealer in the oil passage. At first I thought it may have fell in on disassembly. No way could that have gotten in there. The oil passages from block half to half looked clear and OK (no sealer hanging on the O rings).
The oil pump was another story. Even though I tried to go sparingly on the sealer I also did not want a leak. When the pump was bolted to the block a lot of sealer squished out all over. The clearance between the pump and block are machined almost perfect and you only need a skim of sealer between them. Very tricky.
After thinking it over I concluded that the oil filter should have captured the sealer before it got to the engine. This may normally be the case, but I did not break the engine in. I tuned the engine just after rebuild. This meant driving hard and at high RPMs. High RPMs causes high volume and pressure from the oil pump. Subarus oil filters are designed to bypass the filter at a specific pressure (DP). If you are still with me I now conclude that the excess sealer in the oil pump broke off and blew through the oil filter bypass and into crank main bearing #3. There it had no where to go, but in the way. Main bearing #3 feeds rod bearings #2 and #3. This is why these are usually the trouble children of the rod bearings. They both get fed by only one source unlike #1 and #4.
In a panic I ordered a short block and proceeded to assemble the engine. The above scenario bothered me so I did some searching. I found mention of Anaerobic Sealer when doing Subaru oil pumps.
What makes this sealer better is it will not harden in air. The sealer can be slopped on and will not form hard balls that can be broke off and sent through the engine. A little piece of mind when rebuilding an engine.
Anaerobic sealer is thin so that it does not cause clearance issues. I believe that the sealer I originally used could have caused the block halves to not compress fully and possibly cause the crank main bearing clearance to be to large also.
This would also starve the rod bearings.
I have also switch to 40 weight oil as this was recommended by the engine builder.
$3500 later and I can drive my car again, and doing a real break in. This to me is the most important reason to follow the engine break in procedure. At least the filter should not be bypassed and can catch all the nasty break in material.
Hope this helps you avoid the same problem. Hopefully this solves mine.
VP
Stage 2, 07 STI broken ring lands.
Over the winter from 2010 to 2011 I installed new Mahle pistons. To do it properly I split the block so that the cylinders could be honed to clean them up. New rod and main bearing were installed just because I was there. Engine ran great and didn’t leak at all. A 20G turbo was installed and the tune was done in April/May. I was daily driving just for the fun of it. It was done and life was good.
4 days before my first track day of the year..............
I spun #3 rod bearing on my newly rebuilt engine. At first I blamed Cobbs Flat Foot Shifting as the problem started right after it engaged. http://www.iwsti.com/forums/ecu-tun...-electronics/218716-can-cobbs-ff-shifting-cause-engine-damage-when-not-use.html After more research I have concluded that there were 2 issues and both centered around my poor assembly and the sealer I used. Cobbs FFS was just the straw that broke the camels back.
In all reality there is a short list of things that can cause a spun rod bearing.
Lack of oil
Poor bearing clearance (to big or small)
Improper assembly
Poor bearing construction
Detonation.
Subarus have a poor reputation when it comes to rod bearings. It is why the oil pumps have gotten larger and the crank shafts have been nitrated.
I have read a lot on checking bearing clearances. Let me let you in on a little trick I learned when I was learning how to rebuild diesel truck engines. If its not broke don’t fix it. The bearings and wear looked fantastic, so why go through all the time and trouble checking it all. Stock crank, block, and bearings is what I had and it was in great shape. I just replaced like for like. In other words bearing clearance was not the problem....... sort of.
Poor bearing construction; I spent $380 for a nice shiny OEM set. Definitely not the problem.
Improper assembly; Assembly was checked and rechecked many, many times as I was meticulous with the reassembly. Besides I flogged the engine for 300 miles before it started knocking.
Detonation; Absolutely no sign of it at all. Tune was very conservative and the logs had no knock. Pistons looked great except for all the bearing material embedded in the coating.
Lack of oil; When changing the oil just before the spun bearing I did notice metal flakes in the oil pan. Not good, but it was the first oil change after rebuild. Examining the block after splitting it in half I noticed a BB sized piece of sealer in the oil passage. At first I thought it may have fell in on disassembly. No way could that have gotten in there. The oil passages from block half to half looked clear and OK (no sealer hanging on the O rings).
The oil pump was another story. Even though I tried to go sparingly on the sealer I also did not want a leak. When the pump was bolted to the block a lot of sealer squished out all over. The clearance between the pump and block are machined almost perfect and you only need a skim of sealer between them. Very tricky.
After thinking it over I concluded that the oil filter should have captured the sealer before it got to the engine. This may normally be the case, but I did not break the engine in. I tuned the engine just after rebuild. This meant driving hard and at high RPMs. High RPMs causes high volume and pressure from the oil pump. Subarus oil filters are designed to bypass the filter at a specific pressure (DP). If you are still with me I now conclude that the excess sealer in the oil pump broke off and blew through the oil filter bypass and into crank main bearing #3. There it had no where to go, but in the way. Main bearing #3 feeds rod bearings #2 and #3. This is why these are usually the trouble children of the rod bearings. They both get fed by only one source unlike #1 and #4.
In a panic I ordered a short block and proceeded to assemble the engine. The above scenario bothered me so I did some searching. I found mention of Anaerobic Sealer when doing Subaru oil pumps.
What makes this sealer better is it will not harden in air. The sealer can be slopped on and will not form hard balls that can be broke off and sent through the engine. A little piece of mind when rebuilding an engine.
Anaerobic sealer is thin so that it does not cause clearance issues. I believe that the sealer I originally used could have caused the block halves to not compress fully and possibly cause the crank main bearing clearance to be to large also.
This would also starve the rod bearings.
I have also switch to 40 weight oil as this was recommended by the engine builder.
$3500 later and I can drive my car again, and doing a real break in. This to me is the most important reason to follow the engine break in procedure. At least the filter should not be bypassed and can catch all the nasty break in material.
Hope this helps you avoid the same problem. Hopefully this solves mine.
VP
