Gen V HP500 block.

The top of the lifter valley has these 3 long (plugs?) in place of the standard short oil galley plugs. What are they doing?

Any ides?

if you are using a solid roller or flat tappet cam racers usually install thease to restrict the amount of oil going to the top end of the engine,,concentrating to keep most of the oil in the bottom end of the engine..

if you are running a hyd cam you will need to remove them and install the pipe plugs..

These are what came out of the stock HP500. It had a Hyd Roller?? Oil restrictors are usually installed in the end of the galley's, but these are on top.. Do you think this is something specific to the Gen V motor?

Also, they don't have a hole like a restrictor. They're solid, PLugs?

if they restrict the oil to top of engine(which sounds like they do) they are bad on a marine engine...need the oil to cool the valve springs...we run restrictors in our drag race engines, but short runs cooling is not a factor...

I thought I would post up what I found out about these "Mystery Plugs", in case anyone else ever runs across them.

I spoke to just about everyone I could get ahold of that had any experience with the HP500 Merc motors, and they all had the same answer "Never seen those before". I was able to get ahold of a guy at Merc Racing that was involved with the HP500 program during the mid to late 90's. He said, and I quote, " I remember seeing those, but I don't remember them being installed in any of the production engines. You most likely have one of the proto-type motors from 1995".

He suggested that maybe Merc was testing something for the Gen VI block that was coming out. 1995 was the last year for the Gen V.

So what does it all mean? Who knows.. He suggested I put the plugs back in, as there may have been other modifications made to the oiling system to necessitate the use of them. The fact that the motor had 520 hours on it when I tore it down, and everything looked very good inside, led me to the decision to re-install them as he suggested.

The motor will be on the Dyno in about 2 weeks. I will be paying particular attention to the oiling of the top end, and will post any conclusions.

Do generation 6 454 have those? Bc i am having oil pressure issues im thinking the machinists left them out or the ones in front of cam gear

Yes the Gen 6 block has oil galley plugs in both locations.

JUST TOOK OFF INTAKE MANIFOLD ON GEN 6 454 UNFORTUNATELY THEY WERE IN... IM PREYING THEY ARENT IN IN FRONT OF CAM GEAR.... If they are you think its the spring oil sensors where filter adapter plate goes?

What kind of oil pressure issues?

See his thread "Low oil psi 454 500HP" in general Q & A