[L78toLT1]

I'm in the process of rebuilding my motor after dropping a valve at Road Atlanta. Can someone tell me the part # for the latest GM pump?
My original 2016 pump was still working like a champ when the motor let go, but I don't think I'll reuse it lol! With my mods and over a dozen track days, I'm a litte surprised that it never failed.

[arpad_m]

Originally Posted by L78toLT1

I'm in the process of rebuilding my motor after dropping a valve at Road Atlanta. Can someone tell me the part # for the latest GM pump?
My original 2016 pump was still working like a champ when the motor let go, but I don't think I'll reuse it lol! With my mods and over a dozen track days, I'm a litte surprised that it never failed.

Hey Jim, as far as I know, it's 12686434. This oil pump replaces two previous revisions, and it is the one I have in my car. In all honesty, though, I'd seriously consider the Katech pump instead for your build, it may be difficult to source, but I have no information on what (if anything significant) was changed with the gm unit.

[L78toLT1]

Originally Posted by arpad_m

Hey Jim, as far as I know, it's 12686434. This oil pump replaces two previous revisions, and it is the one I have in my car. In all honesty, though, I'd seriously consider the Katech pump instead for your build, it may be difficult to source, but I have no information on what (if anything significant) was changed with the gm unit.

Thanks, Arpad. 12686434 is the part # I came up with when researching this issue. I agree that the Katech pump is relatively cheap insurance, and will include one on my build, if I can get my hands on one. I find it strange that the oem pumps seem to perform much better on boosted LT1s than on stock LT4s. The additional load and increased harmonics associated with driving the supercharger should be exacerbated by the less robust crank snout on the LT1, yet the opposite seems to be true.

[KingLT1]

Originally Posted by L78toLT1

Thanks, Arpad. 12686434 is the part # I came up with when researching this issue. I agree that the Katech pump is relatively cheap insurance, and will include one on my build, if I can get my hands on one. I find it strange that the oem pumps seem to perform much better on boosted LT1s than on stock LT4s. The additional load and increased harmonics associated with driving the supercharger should be exacerbated by the less robust crank snout on the LT1, yet the opposite seems to be true.

I believe that is because not all the ZL1 oil pump failures are due to the pump itself. A good portion are from a defect in the timing chain tensioner/guide that allows the chain to make contact with the pump and saw a hole through it.

[Mark R]

Originally Posted by KingLT1

I believe that is because not all the ZL1 oil pump failures are due to the pump itself. A good portion are from a defect in the timing chain tensioner/guide that allows the chain to make contact with the pump and saw a hole through it.

Of the pictures I have seen, the outer ring that the oil pump vanes ride against have cracked and broken.

One would think that if the timing chain is fluttering enough to saw a hole in the pump that the cam timing sensor would have alerted to this fact.

[L78toLT1]

Originally Posted by Mark R

Of the pictures I have seen, the outer ring that the oil pump vanes ride against have cracked and broken.

One would think that if the timing chain is fluttering enough to saw a hole in the pump that the cam timing sensor would have alerted to this fact.

I've seen photos of both failure modes. The different harmonics between LT1 & LT4 could be causing more chain flutter failures on LT4s. For whatever reason, both the chain and cracked outer ring failures are far more common on LT4s