Little tapping when start up

[Bru]

Another condition that can cause a ticking sound is "piston slap". That is when the skirt of the piston slaps against the cylinder bore when tolerances are exceeding specification. Either a worn piston or a too large a bore for the piston. Piston slap is usually worse on a cold engine then gets quieter on warmup especially with aluminum pistons which have a greater coefficient of expansion than the iron block. That's why we have head gasket problems on the Supra. The aluminum head scrubs the top of the head gasket more than the bottom on each heat/cool cycle. A stacked metal head gasket solves this problem or increased clamping force on a standard head gasket.

Try this test for Piston slap: When the engine is cold and ticking the loudest, wear a pair of rubber gloves and pull the spark plug wires one by one and replace them in the distributor. If the ticking sound changes you have piston slap (excessive tolerances). Also have a ground wire handy to put in the distributor terminal as you are pulling the spark plug wire out to ground the spark. It may run rough but listen to the sounds. Piston slap means your engine rebuilder wasn't following proper procedures.