Just a random thought, is the intake loose? This was a problem with the 8.1 in the trucks years ago .

Carnuts,

Intake manifold? I wouldn't think so, but I can certainly have a look. I've never put a wrench to it, but that's not a reason it wouldn't have loosened up over time.

I also keep thinking about the ProCharger impeller and that drain plug incident. I don't even want to THINK about what it's gonna take to get that ProCharger out, short of pulling the engine, to check the impeller. I know it turns smooth and free, aside from the obvious over-gearing drag, when turning it by hand.

I also keep thinking about the injectors, and seeing those pictures in my head of clogged fuel injectors squirting out streams of gas, instead of atomizing it properly. That could result in reduced engine power AND raw gas in the exhaust, right?

Would this also be a potential behavior if it were running lean? Could the knock sensor be triggering a rev limiter through ignition retarding? That's what it's there for, isn't it? I don't know. I understand the rev limiter works by restricting fuel, which seems kinda dumb. But how does it deal with a lean condition? Or does it?

I'm open to any and all suggestions.

I know. I know. Read the plugs. I'm working on it.....

Thanks. Brad.
(937)545-8991

Either its not making boost or its leaking boost, in a car I would smoke test for any leaks to put that question to rest. So new plugs , new wires , clean filters, good fuel... have you used an temp gun to make sure all cylinders are hot ( you probably would have seen a bad plug)
can you read the data stream in real time somehow?

I’ve been doing a bit of reading and searching. I keep thinking about the injectors. Where would a guy send them for cleaning and inspection?

Thanks. Brad.
(937)545-8991

Send them to Articfriends on here ( Smitty ) he has done several sets for me and others over the years, top quality job and a good guy

Another vote for Smitty / articfriends. He did 2 sets of 502 injectors for me. Excellent!

Imo you have to see where the boost went. You can't go from 5psi to 1.5/psi and something not be right.

8.1 have weak pistops and are known to break.

If you don't have a boroscope, I would invest in one (cheap on Amazon) and take a look thru each spark plug hole. I wonder if you will see damaged pistons. I hope I'm wrong.

Not sure of the years, but some 496s had an issue with the cool fuel system. There was overspray black paint inside the cool fuel that would flake off and clog the injectors

Underpsi,

I misstated in my OP. The ProCharger kit we have is a 3lb kit, not 5lb. So, it's only "down" about 1.5lb. Since these centrifugal "superchargers" are not linear, there is a possibility that our remaining boost is in that last 500-600 RPM that we are not reaching. After reading several threads here on OSO and a couple other forums, there are a myriad of reasons these 496s drop off this top end, and most of them are either electrical (IAC, etc) or fuel injector related.

I'm aware of the piston situation for this engine. If there were a hole in the top of a piston or three, surely there would be other symptoms, right? I have noticed we are going through a bit of oil (consuming, not leaking), but it's pretty minor. I'm definitely hoping you're wrong, too. 😐

I may just acquire a bore scope, depending on what they cost, just for the academic opportunity. Might have a look when I do the throttle chop and inspect the plugs.

Thanks. Brad.
(937)545-8991

Griff,

I will definitely look into that, too.

Thanks. Brad.
(937)545-8991