Sl 350 3.5 v8 in 1971 roadster,sits a lot it started blowing smoke under acceleration

You have damaged the engine, the smoke is from burning coolant in the engine due to a blown leaking cylinder head gasket or gaskets. Do not drive this or you will completely destroy the engine.

Check all belts pulleys could be injector prob

It basically could be because it has been sitting for so long, but if it keeps on having smoke come. Out it can be a head gasket. Try to let it run if it stops your good if it keeps blowing smoke take it to a shop

Try disconnecting both front o2 sensors and see what happens

Black smoke is excess carbon, blue smoke is oil burning, white smoke is water/steam. Is your coolant level ok?

if its black smoke and id say it is being a deisel it can be injectors or just simply fuel pump timing. get it to a deisel specialist to check the pump timing and your fuel load under acceleration, only real way to get it sorted.

Most likely you have the #4 injector sticking open letting fuel drain into the cylinder when not running and causing a possible hydralock situation. An engine cannot compress fuel. If its not fixed soon you could end up having a bent rod. The #4 injector is the second one from the front on the drivers side.

Hi,
is it a diesel or gas engine?
Usually excessive blue smoke on start up indicates oil is getting into the combustion chamber. It could be piston rings or valve seals.
Quick check, drive it within operating range and speed. Either use the rear view mirror or get someone to drive it and you follow in another vehicle. Accelerate, then take your foot of the accelerator. Blue smoke under acceleration indicates piston rings / pistons. Blue smoke on deceleration or the "over-run" indicates worn valve guides / seals.

White smoke can indicate coolant in the combustion chambers / leaking cyl head gskt, or incorrect fueling. If brake fluid gets into the combustion chamber it will generate a lot of white smoke from the exhaust. However, that would entail a leaking brake master cyl and a leaking brake booster.

Good luck.

Its typical to see smoke on start up on older chevy engines due to worn valve seals. The oil seeps into the cylinder by following the valve stem after the engine is ran.

worn piston rings produce blue smoke all the time especially under acceleration. time for another rebuild or total replacement.. i am not very familiar with metric but thet is still a lot of miles, replace the rings, or replace the engine, or replace the car. it sounds like it is well worn