Evaluating a used engine for a possible rebuild?

[More Power]

Evaluating a used engine for a possible rebuild usually involves looking at specific areas of the engine to determine if it is a suitable candidate for rebuilding.

I'll post some images here if you guys are interested, but I wanted to get your ideas as well.

What do you look for?

MP

[john8662]

When taking apart the few bad 6.2's I've collected through the years I've been looking for cracked blocks and basically looking for what caused the failure of each engine. The first thing I do is pull the pan and look at the main webbing, if there are no cracks, I then pull the heads and get a better look. So far most of the engines I've pulled apart had lots of miles on them, and were just worn. I had one that had a head gasket failure bad enough to seize the engine. Another thing I check is the bearings, some engines that were run out of oil won't have a good crank for the rebuild, because it will require turning undersize. In looking at this area, I think it's best to look for spun bearings, especially spun mains, as line boring is usually cost prohibited. I wish I had better specialized tools to measure cylinder bore, crank journal size, etc.

So I guess I check:

-Main Webbing Cracks, cylinder wall cracks
-Bottom End Bearing Check, crank condition (no spun bearings)
-Cylinder wear, don't want deep scores in cylinder walls
-Condition of heads, cracked beyond repair?
-Anything obvious, thrown rod, etc (structural damage to block)

[84 C2B2]

Having taken my 6.2L apart I came across a few things. I did run a pyrometer and a few times it hit 1100 deg F. It had weeping heads also. You could see this by shining a flashlight up to the block between the exhaust manifold and the head. You could see small bubbles seeping out. I attributed this to my first rebuild and the boys said, "We just put these things on the belt sander to straighten them". No excessive cracks in the precups but a few fell out when one of the heads fell over.
Mostly empherical data on EGT's, recent timing, age of injectors, cylinder pressure, etc. I noticed before I pulled mine that EGT's were high and I figured it was directly related to evil injector spray patterns, high EGT's and improper timing.

Jerry

[Peter J. Bierman]

every part is replacable exept the block.
A cracked block means finding another engine or finding a block and rebuild with the internals from your own.
Parts are readily available so one way or the other you can allways rebuild. :D

But I would look at cracks in block and heads, pistontops for cracks or weird spots and coulors, ridges and scratches in the cylinder walls.
Bearings and blue or black mains and bigends.

Main thing with loose engines is why were they replaced or removed from the vehicle.
An engine without any history is to be given a very carefull examination! :rolleyes:

Peter

[gmctd]

Raise the hood, check over-all engine and bay for coloring - if reddish brownish, could be overheating issues.

Check engine coolant, while noting condition of radiator\heater hoses and radiator - if original, and coolant is clear green, with no greasy detritus inside filler neck, engine oil\fuel\compression were probably not mixing with coolant.

Check engine oil color, and condition of dipstick usually signifys engine useage - rusty indicates long periods of unuse, or has been underwater.
Inside engine condition will probably be same.

Check CDR for condition of blow-by vapors - if oily, greasy ok - if oily, gritty - no way.

Check airbox-to-turbo duct, also noting compressor inlet\blades condition.
If dirty, sandy, oily\gritty - walk away

Check harmonic balancer and accessory drive pulley condition.

Check starter-to-block attachment integrity.

If all checks good, try to get ok to pull pan, check for gritty, then run thru as many of john8662's suggested routines as possible.

[ 02-02-2005, 06:22 PM: Message edited by: gmctd ]

[Dieselboy]

If we are going to get an engine without a record, part of the deal is that purchase is subject to an inspection. The first thing we pull is the pan to check for cracks.

Echoing what Peter said, everything else is replaceable, but the condition of items such as heads and the crank - which aren't typically replaced, but rather refurbished - will certainly influence the dollar amount that the engine is worth.

[Peter J. Bierman]

Tomorrow I can put all this to the test when I go to inspect a 599 6.5 shortblock I'm after for a wile :D

It spun a bigend bearing but the crankshaft is suposed to be undamaged.
They did most off the work allready, the heads are off, the engine is out of the vehicle and they dropped the pan.
All I have to do is look for the signs ;)

Wish me luck,

Peter

[Peter J. Bierman]

Bummer, block had all 3 center mains cracked :mad:
I drove 450 Km's to see a cracked block.
But I'm glad I did, otherwise I would be the proud owner off 500 pounds of scrab metall ;)

Anyway, the search continues,

Peter