Guys need some help. Recently acquired a sbc 088 Vortec engine with unknown cam. It had been sitting for about a year and the carb was in need of a rebuild but ran decent. Long story short I’ve replaced everything that bolts to the long block. It ran decent for a few miles and then the plugs turned black and sooty. I’ve verified timing with a tdc tool as the balancer mark was off. Now when I blip the throttle it want to sputter back thru the carb and shoot the occasional flame. I verified timing again and then pulled the plugs and noticed how black they are. Need some advice. Specs below.
350 Vortec with 1.54 pistons (so I assume they are .045 in the hole and horrible quench unless previous owner milled the block more.
unknown cam but it’s mild as the Vortec springs appear stock.
Quickfuel 650-q carb (stock and the accelerator pump shoots good as soon as I give it throttle)
Accel HEI distributor
Ran TR55 plugs gapped at .045 but just purchased some 3926 to try a hotter plug.
edelbrock rpm intake
Hv oil pump (60 at idle)
6.5 psi fuel and floats are in the center of sight glass.