Decoded VIN

[acountryclipper]

I just decoded the VIN on my 86 chevy 3/4 ton and the engine code says it has a 350 heavy duty. does the heavy duty mean that it has a 4 bolt main or what?

[Captkaos]

It means it is the low emmissions model.  It "might" have 4bolt, might not...

[Fast68Chevy]

heavy duty emissions

normally is vin engine digit code M

bolt mains will be random

these usually had the TCC system with a relay mounted on the pass side valve cover, and virtually no other emissions equipment and no cat converters either, and commonly were equipped with factory dual pipes, 1 ton and some 3/4 ton pickups and vans both if are over the required GVWR


good luck