Question : Identifying a vibrating mystery engine.

[ndsharp]

I am helping to swap out an engine in an 84 S-10 pickup. We got an 86 Jimmy with a bad transmission to take the engine out of for out S-10, but it turns out that the engine in the Jimmy was not its original either and the people we got it from don't know what vehicle it came out of.

After getting the new engine into the S-10 and starting it (finally) there is a very pronounced vibration to it. After doing some research, it was discovered that some of the newer 60 degrees are internally balanced (ours was externally balanced.)

How do we identify the engine that we have in the truck now? I never did find where it was marked with any meaningful numbers.

Is there any way of telling if its internally balanced without taking the oil pan on (its a huge pain to get off. You have to wither lift the engine or slide transfer case forward)

Thanks in advance. I have loads of pictures and video of the shaking if it would help anyone.

-- Nick

[geoffinbc]

If you put the external balance flywheel/flexplate on then switch it. It is the only thing that causes a vibration at all RPM. The only way to tell the balance is to know the actual build date of the motor or to look at the crank.

[60dgrzbelow0]

Is there any way of telling if its internally balanced without taking the oil pan on (its a huge pain to get off. You have to either lift the engine or slide transfer case forward)
Thanks in advance. I have loads of pictures and video of the shaking if it would help anyone. -- Nick

Last year, I ran into a problem of not being able to tell whether or not some crossing header pipes made by Pacesetter were fractured, cracked or worn through at a certain crossover sections where the pipes almost were touching. The only way to definitively find out was to use a Fiber-Optic Borescope. I'm not certain one would work in this gooey of an environment of a freshly drained crankcase, but if Geoff (betterthanyou) can confirm that the center-notched balance weight of a Distributor-less Crankshaft can be viewed internally by means of snaking a Borescope inside via the Drain Hole of the stock crankcase, then it might be worth a try. I borrowed the one I used from a local machine shop and machinist friend that I've used on more than one occasion and it was internally lit well enough to see clearly all way down inside the header tubes. If you're lucky enough to snag one on loan, as long as the scope is flexible enough... I think it would only take a few minutes for you to find out what kind of crankshaft lives inside that engine.

[60dgrzbelow0]

Here is a bit more information on the variation with crankshafts for early model GM V6 Engines:

The Externally Balanced Crankshafts were installed in engines manufactured between 1980 and 1986.
The Internally Balanced Crankshafts equipped with a Distributor-less Ignition System slotted timing disc were introduced in 1987.
The Internally Balanced Crankshafts destined for Front Engine vehicles began in 1987-<.
The Internally Balanced Crankshafts destined for RWD vehicles began in 1988-<

You can identify the differences in all these crankshafts by the following information. (This is a partial list...<betterthanyou> may have some more data on these):

Casting # Type of Balancing Journal Diameter Type of Rear Main Journal Surface Type of Original Oil Seal
---------------------------------------------------------------------------------------------------------------------------------------------------
504 External Small Knurled Rope (or Two-Piece)
504 External Small Smooth 5mm One Piece
209 External Large Smooth 10mm One Piece
817 External Large Smooth 10mm One Piece
481 Internal Large Smooth 10mm One Piece
526 Internal Large Smooth 10mm One Piece

Data Source -> "How to Re-Build Your GM V6 60* Engine" by Tom Currao

[60dgrzbelow0]

And again... JICYNI...here is a bit more data on the 3.4L L-32 Engine:

Automobile : 1993-1995 GM Chevrolet Camaro-Pontiac Firebird
Part Name : V6, 3.4 L, 207 CID
Description : RWD, block #608, cast iron heads #884, crank #981, employs crank & cam sensors
Engine Size : 3.4 L, 207 CID
Engine Type : V6
VIN Code : S
Head Casting : 884
Block Casting : 608
Crank Casting : 981

[60dgrzbelow0]

This video covers the repair of a blown out spark plug on a Ford Triton Motor ...but central to this repair is the use of a BORESCOPE that demonstrates its utility and perhaps something like this will save you a great deal of agony if you can view the crankshaft using something like this:

http://www.youtube.com/watch?v=qDL3i6mT8V4&NR=1&feature=fvwp