Power will increase considerably, but so will fuel economy. If you live in an area where they don't require emissions testing, or at least don't look at the exhaust, at least get rid of the catalytic converters, better still, put a nice exhaust system on it, and get the ECM tuned. It's a tough big block that makes really good torque, with proper maintenance it should go 200K+, and possible 300K+ before needing anything serious. And I went back to the GM AC Delco double platinum plugs. My truck will be down maybe 1/2 quart or a little more between oil changes.Īt 96K miles I replaced my plug wires with Taylor wires to resolve a slight misfire under acceleration. I use 20W-50 Royal Purple in mine, and because it is a 2 wheel drive, I use an AC PF 932 two quart filter. Change them, the deposits can cause enough resistance to create a misfire, and could cause enough load to kill a plug wire or coil pack. The PCV system design will cause deposits to build up on the plugs, usually at 25-30K miles they'll look a little rough. It's simply picking oil up through the PCV system built into the intake that has the pick up in the wrong location, and a serious lack of baffling. It is not getting oil past the rings, or past the valve guides and seals. The vast majority of them are actually sucking some oil from the lifter valley under the intake manifold due to the design of the PCV system. Some of them use a little oil, maybe 1 quart in 3000-3500 miles. Some of them have slight piston slap when cold. Wouldn't trade my 8.1 for any diesel of any type or brand.

2004 8.1 vortec mpg