SBC 350. Using between 1/2 and 1 full quart in about 40 miles of driving, highway or in town. I'm pretty new to working on cars, and I'm trying to make this a bit of a daily driver. I'm not sure where to go next. I want to find the problem and fix it. Thanks. No obvious major oil leaks. Not a dop under the truck in its parking spot. Exhaust has no obvious color or smoke. Some smoke under initial hard acceleration, which I would think is normal. My exhaust goes straight back then out the sides a little behind the cab. The end of the pipes have a black sooty oily coating on the inside. I've done: New PCV valve Added a 1 inch spacer to Holley 650DP with a port for PCV Added baffles to valve covers Tried 3 different oils Mobil 1 10w-30 Carquest 10w-30 (seemed to show some improvement but not convincing) Valvoline VR1 conventional 20w-50 Had the bowtie heads re-done at local shop for a separate problem (two bent valves) Basic compression test 1 - Dry 144 Wet 144 2 - Dry 118 Wet 122 3 - Dry 141 Wet 145 4 - Dry 145 Wet 151 5 - Dry 145 Wet 147 6 - Dry 126 Wet 129 7 - Dry 148 Wet 149 8 - Dry 131 Wet 134 New spark plugs (ones with about 2,000 miles on them looked terrible Retarded the timing some I did not build the engine, but talked to the builder. He says: 6000 miles on it or less Bored 0.40 Over Flat top Pistons High Volume Oil Pump X Rods Hardened Push Rods Harland Sharp Roller Rockers 305/25 Comp Cam Double Roller Timing Chain Holley 650 DP Victor Jr Intake With the new plugs and retarded timing, it's running great, but still "using" a lot of oil. I would gess the plugs are going to foul and it'll start running worse again. What should I do next to find my problem? Straight 40 weight oil? Buy and use a leak down compression kit? How do I check that the valve guides were done correctly?