i have a 87 r10 truck that doesnt have the stock motor how do i tell the size of the nonstock motor that ithas

Answer 1

There will still be a serial number stamped in the block and this will tell you the engine size or original cubic inch displacement.

Also, most engines have different exhaust manifolds for the various cubic inch displacements even if the blocks are otherwise identical in size. The cylinder heads have recognizable casting variations to the trained eye, too, and as mentioned have different exhaust manifolds bolted to them per the size of the block cubic inch displacement they are designed to compliment.

Good Luck!