i have built another ls vtec motor only 500 miles right now and finally ran into the problem of smoke in vtec. did compression test got 240 across the board with pr3s and leakdown test came out good! is it my valve guides or seals maybe? nothing building up on plugs as they stay a tan color and electrodes stay clean. smoke is blackish grey and some blue cause it uses a little oil at 500 miles used about a half quart and just did my second oil change for the 500 mile change for break in and some times it smokes some times not as much. ive done lots of ls vtecs since 2003 never had one smoke like this in vtec. done a usual beat on it then vacum pulls letting it gear down all this time and only did a hone on the block and block was still in exellent shape just went to ls v with b16 head and pr3s and didnt smoke with the pr4 ls pistons and head before. theres no leaks. head was resurfaced out of 99 si with 99xxx miles on it but it only had a puff at vtec engagement but the head sat for a couple years. also on a block with no breather box so i have a catch can an drilled the valve cover for the pcv valve just like the ls one was, no oil in catch can yet, one line melted a bit but i dont think it would suck together as vacum is almost non existant in vtec rpms i think. sorry so long but trying to cover all i can,any help is appreciated!