Ok, went out to airport and checked my water pump.  It has four

bolts

retaining the pulley, however, there are holes for 8 bolts.  I am

pretty

certain it came with 4 bolts and the pump is an 86 model.  I do

have

two

observations which may (or may not) have bearing on the failure

mode.

My

belts run on both sides of the pully.  One wraps around the main

pulley,

around the water pump pulley and then down to the airpump pulley.

The

other

one wraps around the main pulley, around the opposite side of the

water

pump

pulley and then around the alternator.  Don't know if this

presents

more

of

a balanced load on the pulley or not, but would think so.

Also, my main pulley is an underdrive pulley by 20% and I rarely

run

the

engine higher than 6000 rpm (cruise around 5300-5700), so those

factors

MAY

reduce the stress on the stock water pump pulley.  Did not do a

dry

crack

check, will do that later.

Ed Anderson

Hi Ed
How about installing 4 more bolts. Just for me! Tracy has 8.
I am going to check pulley runout with a dial gauge this weekend.
My main pulley is also 20% underdrive. I cruise at WOT leaned off the

scale

at 6200rpm. 500kn miles with 1 hour reserve.  Eaten into reserve twice

now.

Ian, (8 bolt Beadle) Australia.

Totally agree, Ian.  It certainly can't hurt and from the stress analysis
that Dan ran, it looks like 4 more bolts would help quite a bit.  Perhaps a
cap as Paul mentioned of 4130 with the 8 bolt holes through it.

Ed

 
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