John Barton continues hos article on the GPW engine

rebuild this time he tackles the fitting of the Crankshaft.

The main and connecting rod bearings used in the jeep

engine are two semi circular halves called inserts. When

installing these in the block and connecting rods, some care

must be observed. If there is good clean oil, and the engine

is not abused, they can last a long time. As long as there is

an oil film, the rate of wear is slow. Grit or dust getting into

the oil, either through the carb, or from installation, can ruin

a bearing. In my pictures, you can see that I use a lot of

assembly oil. But, by having everything ready…I get it

closed up quickly. I wipe up excess- no oil should get on

threads or bolts…to get proper torque, they need to be

clean and dry. Wipe down all bearing surfaces, there should

be nothing behind an insert.

This is how the crank-

shaft comes from the

machinist. Leave it in

the bag until ready to

install. The journals are

precisely ground and

polished. Scratches, etc

are no good, and they

will rust in a minute. The

tag indicates that this

crank was cut .040

undersize on mains and

rod journals. From old

inserts, you can see

what old size was. This

crank was .030/.030. So

it was cut the minimum,

increments are usually

.010.

As with the valve train parts, I lay out everything. I assem-

ble pistons first.

The pistons must be assembled with

T-slot and squirt hole in correct rela-

tionship. They must also be installed

in cylinders with offset in correct

relationship to main bearings. The

connecting rods may be numbered,

check during disassembly. The num-

bers, letters, dots, etc. can be on

either side. You can’t always use

them as a reference. Cylinders are

numbered 1-4- front to rear. Often

one rod has been replaced. So, you

must use correct assembly and off-

set to install. As shown in part one,

pistons often have an arrow on top

pointing to front. Use the arrow, slot,

squirt hole, and offset to check that

pistons are assembled and assigned

correctly.

By

John Barton, USA

Gpw eng rebuild Part 2.qxd 11/03/2008 18:26 Page 1