I obtained a running, 1998 454 Mag MPI 385 hp, complete engine , ecm, efi etc. I understand this engine has forged crank, forged pistons etc. I have it from two sources that the OEM pistons are from JE, but I have conflicting information on the valves. Are they stainless, or Inconel valves ? My project is to swap out a 2000 7.4 L29 454 for this engine, and I have my choice of rebuilding the entire engine or just doing a valve job (some valves / seats are known weak based on leakdown team). The 385hp engine has 250 hours on it, so based on the findings of the teardown I might not even touch the block.

Any advice on rebuilding the engine would be appreciated as I am going to do most of the work at home myself. My first question is on the stainless valves and any other issues I would watch out for. Thx in advance.

I would just get valve job and spring with only 250hrs. The bottom end should be good to 1000hrs.

That motor has forged pistons, but I think they GM, not JE.

As Griff said, do the valves and springs and have the shop check the valve seats when they resurface the heads.

Use Manley or Ferrea (sp) inconel and stainless valves.

Then you'll have a good motor for at least 500-600 hrs.

There is a very hard to find (and out of print) book called "Rebuilding the Gen V / VI Chevy Big Block", oringinally from HP Books. I was able to find a copy from a guy in the UK. This book indicates the part number on the pistons used in the 454 HO and 502 Gen V / VI engines, and that GM sourced the original pistons from JE. This would make sense for a low production volume engine. I would not be surprised if JE supplied other products to both GM and other brands, but until I tear down the motor I wont know, and may never know unless JE puts their stamp on it. Hopefully the pistons will be fine- I instead to only put a fine hone on it and install new rings. Obviously I am working on a budget here