Re: Fng
There were 4 engine options for the `71 177 swinger;
L4 120 and 140 hp Mercruiser, L4 130hp Volvo Penta or the V6 155 HP OMC.
How to specify what 4 cil engine you have there..
The 120 mercruiser is a 2.5L (153ci) GM and has
no harmonic balancer, just the belt pulley on the crank, the 140 is a 3.0L (181ci) GM and does have a harmonic balancer.
The 130 hp 2.0L (121ci) Volvo-Penta reads Volvo and B20 on the block casting and Glastron custom on the chrome valve cover.
This is a B20 Volvo car engine.
The 2.5L GM is also used in cars but the 3.0 L is not!
The 155hp OMC is a V6 buick engine.
http://www.classicglastron.com/71gl-v176-177.html
Good luck!