Quote:
Originally Posted by skyphix
I can't comment on the manifold;
How much boost you can run will be determined entirely on the condition of your shortblock and the tune. 10-12psi is common on completely stock internals - adding some ring gap is protection, and depending on how hard you run it, enough heat will cause that ring gap to close (if it isn't wear-widened) up enough to break the ring land or top of the piston. If it were me, I'd start at 8psi... see how the engine likes it, work with a tuner familiar with boosted applications and GM ECU's, and work up from there. Every engine has had a different life and behaves a bit differently.
You don't need to do a Speed Density tune (MAF-Less) - but it does make life easier in boosted applications. If you want to run a MAF for whatever reason, your stock setup is tunable at 10-12psi, and custom OS's are available for 2 and 3 bar applications. The stock MAF can be rescaled but only to a certain point... I'd say 1 bar (15ish psi) would be the limit of rescaling before you run into inaccurate air metering, but it depends on other factors (including your injectors.) It really is about airflow, not boost or no boost. My opinion here would be to do whatever your tuner is most comfortable with and can get you the safest tune on.
All in all, 10-12psi on a stock engine is perfectly attainable... as long as the engine is in good health. If you want longevity, don't beat on it too hard and run a very conservative timing table, "over injector" (i.e. bigger injectors than you need) and "over fuel pump" (more fuel pump than you need) will keep things save, avoid a sudden lean under boost condition, and keep your engine together. Opening the ring gaps would definitely buy you more leeway, but if you're in that far... gen 4 rods and pistons AND slightly wider ring gap... and then it just snowballs from there.
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Yes, VERY helpful information. The engine situation is a hard call for me. I also have a running 280K mile 6.0. I know with a cam it could make way more power than the 5.3. The rings are probably plenty worn but I'm not sure of the condition of the valve guides, bearings, etc. and I'm trying to avoid a full engine rebuild. I know the 5.3 I have is a great engine, I used it for 7 years in my 56 gmc. Plus, if I don't stick my foot in it all the time I might even be able to sneak past a gas pump now and again. The 6.0 I rebuilt with a 224R cam made me lose 6mpg when I swapped out the 5.3!