Back in January of 2007 I did an article about the differences of
the 1992-2004 3.2L Isuzu components and in particular the different
crankshafts.
I also remarked that the 3.5L crankshaft is identical in appearance and
dimensions and that only the stroke is what made it different.
One part of that article worth discussing again is the method of
identifying the 3.5L crankshaft found on the front and rear
counterweights. There is a shallow groove machined into both of them on
the OD (see Figure 1). However, this gets a little tricky sometimes
because many cranks may have a "tooling drag" line on the OD of one of
the counterweights. Don’t be confused by a "tool drag" mark that I,
too, have seen on many cranks: you must make certain that the
distinctive groove is present on both the first and last counterweight.
Now, before you start thinking that I am a slacker who has packed it in
for the year, started preparing for the holidays and that I’m just
handing you a bunch of rehashed goods, let me tell you why I bring this
up. The old school of hard knocks recently reared its ugly head at
ProFormance Powertrain during a run of the 3.5L Isuzu engines.
During the final stages of assembly, while rotating one engine, it
suddenly locked up. On the bottom end of the engine there is an oil
manifold that bolts onto the top of the main bearing caps – the
crankshaft assembly was hitting that manifold. Fortunately having a
number of these engines sitting side by side in the same state of
assembly we could easily see that none of the others were in the same
condition. So why was there a problem with this particular engine? The
oil manifold was different – it did not have reliefs in it like all the
others (see Figure 2).
We soon discovered that the oil manifold without the relief notches
as shown in Figure 2 was a manifold for the 3.2L Isuzu’s shorter 77mm
stroke crankshaft and that the manifold for the longer 85mm stroke
crank in the 3.5L engine requires a little extra clearance. Now, you
can certainly use the 3.5L manifold on a 3.2L but not vice versa. So if
you ever have 3.2L and 3.5L engines in your facility at the same time
you’ll want to make certain that the right oil manifolds get on the
right engines or you could have a serious problem if it somehow gets
out of your building unnoticed.
Practical Builder Tip
Next I want provide a quick PBT (Practical Builder Tip) that has come a
up a few times on an engine that we all know backward, forward and
upside-down: the 350 Chevrolet. Not long ago, I came across a situation
that made even me do a double-take. The 1996-2000 vintage 350 four bolt
main block (c/n 10243880) can come with a water pump bypass hole or
without (see Figures 3 and 4).
When the engine went to Vortec cylinder heads the water pump bypass was
no longer needed, so the cylinder head (yes the head) no longer
included a coolant port to accommodate the passage (see Figure 5).
What I forgot when confronted with this situation is that the water
pump bypass port went from the front of the engine to an intersecting
port/channel that ran vertically to the deck of the block, then met
with a mating port on the cylinder head. Since the Vortec head does not
have that port, even though your water pump may not cover the opening
it’s no big deal. There is no active coolant flow to the bypass hole
anyway, so what difference does it make? None.
Of course, there are the doubting Thomases out there who will blow into
that hole with shop air pressure (100+ PSI). In such a case you will
get bubbles in the cooling system because the system was not designed
to withstand that high of pressure. Try blowing with 22-25 psi and it
will be sealed tighter than a drum. So when you get that "my water pump
does not cover the lower hole on of the block on the driver’s side"
call, remember this: if it is a Vortec engine you have no worries –
there is no coolant there anyway. 
