Greetings Shane,
Welcome to the GMT400 forum. There's a lot of hard-won hands-on
experience in here, so if you are a sucker for knowledge you've come to the
right place. :0)
You've already gotten a lot of good guidance surrounding the 3 main paths
from here to getting your truck back in service. (1-Rebuild what you've got, 2-LS swap it,
3-Find a previously-enjoyed 454 & swap that in...btw, I liked
@Xombi 's idea about the
motorhomes -- I recently did some electrical work on a late '90s motorhome with a 454 in it,
very low miles on the odo, and it ran so smooth, quiet, & was obviously well cared for.)
Anyway, I thought I'd try to answer a couple of questions that you had posted earlier.
*
Chevy V8 cylinder numbering scheme, and then which 2 share the front crank throw:
Different manufacturers use different numbering
methods, but in just about all V8s the #1
cylinder is on the front of the 'most forward' cylinder bank. It's subtle & easy to overlook,
but on the BBC the driver's side cylinder bank is the width of a connecting rod closer
to the radiator than the passenger side.
Therefore, on the SBC, BBC, & LS motors the 1st cylinder on the driver's side is #1. And then
(unlike F*rd) Chevy used the street-style numbering scheme -- odd on one side, even
on the other.
Pulling this all together, you end up with the following:
Passenger side
* 2 - 4 - 6 - 8*
*1 - 3 - 5 - 7 *
Driver's side
(Note: Refer to the attached photo for details.)
Given all this, the front crankshaft throw photos you shared with
us have the #1 & #2 connecting rods showing.
*
Side to side (front to back) 'play' on the connecting rods:
In order to allow the crankshaft to move a few thousandths of an inch
front to back during normal operation, and also to allow the connecting
rod pair to share the common crank throw, the wrist pin is clinched by
the small end of the connecting rod, but at the same time the wrist pin
can move freely side to side a small amount from the nominal center of
the piston. (Apologies for the run-on sentence. :0)
This is something that takes an hour to explain via the written word, but
makes perfect sense if you have a piston/wrist pin/rod assembly in your
hands. Note: Most people don't realize that when they depress the clutch
pedal on a stick shift vehicle, they are actually trying to force the crankshaft
out the front of the engine by however many pounds worth of clutch spring
in the pressure plate. (!)
With a healthy thrust bearing (vertical part of the rear main bearing) the
crank is only allowed to move ~.006" front to back. As you can see, if we made
the wrist pin setup so that it was always/only in the exact center of the piston,
then this front to rear crankshaft movement would transfer large side forces into
the piston/cylinder wall area. Yikes!
It's kind of a long explanation, but it's possible that the sideways connecting
rod (wrist pin) movement you observed is a feature, not a fault. Wish I wasn't
doing this remotely, for I could show you all this in less time than I can describe
it with words.
*
FOD inside the engine from the failed front rod bearings:
FOD =
Foreign
Object
Damage. Metal shavings inside a modern close-tolerance
engine is bad juju.
However, IF the rod bearing issue was caught right away
(ie: unexplained lower oil pressure observed and engine immediately shut down)
then when you drag a magnet through the mud on the bottom of the oil pan
and
none of the mud is attracted to the magnet, then only the (softer) rod
bearing material has been worn off/deposited inside the engine.
Let's say in this best-case rod bearing failure scenario that the crankshaft surfaces
still look good/measure within tolerances. In this case, a betting mechanic might get
away with just a quick polish with 600 grit sandpaper and new bearings. A slighty
more conservative approach would be a new crank & bearings, but still leaving the
rest as-is. Maybe not the most prudent way to go for an ambulance engine, but
plenty OK for an old plow truck that never leaves the Ponderosa?
On the other hand, the photos you shared clearly show that the engine was run
long enough after the loss of oil pressure that in addition to the rod bearings the
crankshaft surface is
also ground away. The shavings from the crank are both ferrous
& hard, and they will definitely be attracted to a magnet.
In this case, all that hardened metal has got to be completely cleaned out of the
engine. And every single part inside will need to be inspected from the "damaged until
proven good" perspective. Some might argue that the oil filter will have kept all that
FOD out of the inside of your hydraulic lifters, timing chain, rocker arms, wrist pins,
cylinder walls, etc...but this never happens to me, I always find that all these parts
are toast. :-(
Don't get me wrong, it can be fixed, but it will require a complete do-over.
*
Rebuilding vs a crate motor (same as original or newer LS)
I could argue either side of this depending upon the day, how motivated I felt,
and how much I have set aside in my rainy day fund.
Lots and lots of car guys vote with their wallets for a crate motor, and usually
use 'the warranty' to help justify why they did it. Elsewhere,
@Schurkey
gave a convincing & factual detailed explanation of all the different ways that 'the warranty'
can be made worthless. (Basically, you are at the mercy of the folks on the other end
of the phone.)
On the other hand, there are a lot of very happy crate motor owners out there. This
comes down to just how lucky do
you feel with service after the sale? :0)
****
I definitely fall into the 'rebuild what was in there' camp. No doubt that there are as many
opinions about rebuilding engines as there are people in this forum. And I don't think that
I am going to change any minds, but I will share this truism about rebuilding an engine.
*** I am only as good an engine builder (assembler) as my machinist is. ***
My first few engines were OK, but each had it's strengths & weaknesses. But the more
I built (and importantly, the more I researched engine blueprinting) the more I realized that a
great machinist allowed to 'get it right' based upon his years of experience = the engine
lasting longer, running smoother, and being something to look forward to driving with a keen
ear listening to the motor music in the engine bay...instead of constantly listening for and trying to
figure out where the pinging/slapping/knocking/tapping/rapping sounds are coming from.
:-(
I will admit to being pretty clean & careful while assembling any engine, but the world is just
that much better when I've had a crackerjack machinist involved during all the heavy lifting
prior to the assembly session(s).
To give you an idea of what I'm talking about, there's an old-school father & son machine shop
somewhere out in CO that make these zen-like videos of remachining engine parts back to
new specification. The Dad has been doing this for 40+ years, and his son is coming up to
speed on all this...and is putting up well-edited videos for our viewing pleasure.
If you are interested in how a wounded crankshaft like yours would be restored to a new,
fully functional condition, then this is some destination watching for sure:
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Bottom line, you know how foodies have 'destination restaurants' where they won't hesitate
to travel significant distances in order to enjoy the cuisine? I'm that way when it comes to
machinists. If all the local dudes are either too busy / too disinterested / too precious when
it comes to the engine rework I need, then I'd much rather take it to the old perfectionist
Merlin-type out in the country with older well-oiled machinery who takes the most pride in his
work of all.
****
All of the above is just food for thought. And given your comments about wanting to learn
more/possibly building an engine someday, I thought I'd stir the pot a little.
Me? I'd try to find one of those affordable motorhome 454s, throw that in, get the truck running,
view this as a semi-temporary solution...buy an engine stand, put the wounded 454 on it...and
then be able to build it/learn it without all kinds of pressure to rush through it in order to get the
truck back online. Will all this cost money? Yes. But so does
any kind of education (formal or otherwise)
that will give you the real-world ability to fix similar issues down the road for the best bang/buck ratio. (!)
And If you do it right, the sense of accomplishment while driving around in something propelled by
a powerplant that *you* built is
unsurpassed.
Well, at least in my world. Your mileage may vary. :0)
Best of luck, and keep sending us updates -- you have a guaranteed audience, especially with
those pics! And if you hit a snag, there's several folks in here who've already hit that same
snag and figured out a fix for that...
