Here's a head scratcher!!! !!!
 

rebuilt ls1, 243 heads, cam, headers. 5k miles on build. Everything has been perfect until now. Im getting blue smoke out of my exhaust, but only when braking harder than normal. Nothing on accel, nothing at idle, nothing upon cranking, only when coming to a quick stop. I can take it out of gear so that im coasting with engine close to idle and make a quick stop, and it start puffing alot of blue smoke. any ideas

Maybe a bad valve seal lotta oil puddling up around it on de-cel, then getting by the seal and into the chamber.

BUT....doesnt smoke on decel.

(De-Cel) Meaning you using the brakes causing the rear of the car to lift and the nose to plunge, this action could be causing the oil to rush up and submerge one of your seals. Just a thought. Are you sure the car doesnt do it when accelerating?

100% SURE. only when coming to a quick stop. Kinda like the pcv sucking oil and dumping it in the intake

wonder if you have excessive oil in the intake from the pcv and only on quick stops it moves forward enough to drip down into the runners and create the smoke? Look in your throttle body and see if there is signs of oil in the intake.

there is some oil in the intake. found a little metal in the oil too. i changed the oil at 1000 miles after the rebuild. hmm

agreed... Maybe somehow the oil is sloshing forward in the heads and getting into the pcv sys when nosediving under hard braking. Just a thought but try unhooking the pcv hoses from tb and int and capping the tb and int off for a quick run and let the pcv sys vent to atmosphere to see if smoke clears, If still doing it then atleast you will have eliminated one scenario from the puzzle. Post back and let us know.

will do. im a little nervous about the metal shavings now. changed the oil at 1k so this will be the second one since the rebuild.

get a oil catch can system for the pcv system.do a compression check,and look at you plugs.

Who did the engine assembly, and what valve covers are you using?

Not real unusal to see some metal on a fresh build. Cut oil filter apart after next oil change and inspect.

your head scratcher is in the brake booster. it's leaking!!! prabably? hows your brake fluid level? remove the tube from the booster and see if there is any oil.....

ok, here's an undate. changed the oil yesterday evening. theres some metal shavings but not an extreme amount. just enough to cover the end of the drain plug. this is the second oil change since the build so maybe its still shavings from being new. idk. i did the build. using the stock ls1 valve covers. i disconnected one of the pcv hoses from the throttle body and plugged it up. that cured about 90% of the smoking issue. still may be some oil in the intake from before. if this keeps acting weird, im going to pull the oil pan just to inspect. OR i'll end up buying a 6.0. muahahahaha

Sounds good. What end gap did you set for the #1 & 2 compression rings?

NO CLUE. just what was set with the stock kit