HELP 2 minutes to 12o' clock - Disaster averted - Advice/Help needed

FluoFerret

Greasemonkey
Apr 2, 2018
184
43
Luxembourg
Hello everybody!
I had to pull the engine from my G-Body and I want your advice on this matter, there's some "history" before, so here goes:
in 2007 I installed a GM Goodwrench longblock 350cui SB in my Lemans, coupled to a TH400. Since then, the car has driven around 7000 miles (at max). It had sidepipes until this spring 2022 and it always felt somewhat sluggish in performance (diameter through mufflerpack inside too small for the engine, choking it), so I scrapped them for dual 2,5 exhaust with H-Pipe. Car ran a lot better, more responsive and more torque/power.

Here's the disaster build-up:

After a month the engine started to "choke" and slow down when driving on the highway (60-70 mph) for more than 10 minutes, but releasing the accelerator and allow it to reduce speed and RPM always brought me home safe and sound.

Two weeks ago towards the end of a 3 hours cruise, driving uphill, the engine started to "choke" again, around 30-40 mph, dropping rpm and speed didn't help, and I stopped. in idle and neutral the engine performed well, and after 5 minutes I continued driving for a mile and it happened again. this time I stopped, let the car sit for 15minutes and started driving again. I got home without any further incident, however i was soft on acceleration.

At home I checked the transmission fluid, its still a nice clear wine-red, so most likely no issue there, but a go-around the car i saw that the left exhaust pissed oil. so I pulled the spark plugs. this didn't look too good.
20220615_181520.jpg


Next step was checking the the valves from inside with an endoscope... there was oil dangling from most of the valves, and they were burnt. badly. the funny part is: no blue or white smoke while driving or idling. only the smell. here's an example of what it looked like:
20220621_181145.jpg
20220621_204412.jpg



checked the compressions, and they were between 8,5 (lowest) and 9,5 (highest), engine should have 8,5.
i first thought the cause were only the valve stem seals until my guts pushed me to pull the entire engine out and check everything, since my engine-oil always ran "hot" but never smelled burnt (have an extra oil-cooler installed)
by tearing the engine apart, here's what I discovered:
  1. Oil filter screen fell off the pump ( don't know when and why). pump intake was always submerged though since i always had good pressure on the gauge
  2. Flex-plate bolt holes for the torque converter were "worked" out of shape
  3. No visible metal particles in the filter (cut it open)
  4. Thrustbearing of the crankshaft was grinded down giving the entire crankshaft 0,043" of endplay. That's just beyond good and evil.
Here's what the thrustbearing and the crankshaft (destroyed) look like:
20220819_163838.jpg
20220819_163833.jpg
20220819_163802.jpg


I now know why my engine oil was always too hot: it picked up a lot of friction heat when being pumped through the rear main journal. Without the extra cooler after the temp sensor, the engine would probably have given up a lot earlier.
The good news is, that the cylinder-walls themselves are still perfectly intact, since they all still have clearly visible criss-cross pattern from the honing. The other bearings of the crankshaft were all in great condition though. no excessive wear nor damage.

it is quite obvious to me now that the engine "choked" because for some reason, the crankshaft endplay worked against the pistons travel up/down the cylinders. The problem is: my converter seems to be undamaged and no obvious signs of "ballooning". The cylinder heads are damaged too, and the cost to refurbish the valve-guides are way above the cost of new ones (at least where I live).

And that's pretty much it for my "expertise" right now. If anybody could help me with further information on what else to check, on what could have caused all this, and what to do better when rebuilding, I would be forever in your debt ;)
I can provide additional pictures of the teardown.
 
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ELCAM

G-Body Guru
Jun 19, 2021
706
93
Can you take pictures of the pump drive on the torque converter and pictures of the flexplate? Also pics of the PCV system.
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
1,220
113
How much room was between the converter and flex plate unbolted? Did the converter slide easily up to the flex plate?
 
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FluoFerret

Greasemonkey
Thread starter
Apr 2, 2018
184
43
Luxembourg
How much room was between the converter and flex plate unbolted? Did the converter slide easily up to the flex plate?

Honestly I don't know. The engine/transmission got installed by a shop that once had my full trust, but over the last 10 years i discovered so much crap-work of theirs, that I doubt they did it right on my car when hooking up the converter/transmission to the engine. for example: when they swapped the V8 in, instead of readily available V8-supports, they just used the V6-supports, trimmed the mounting holes off and welded that sh*t into place backwards. here's a pictures of this "work of art".

20220724_154141.jpg
20220710_163914.jpg


thank god it was welded like an amateur, so I was able to grind that off, and install OEM motor mounts. this is how it looks now. it will give the engine a completely new "angle" in the engine compartment... literally.
20220726_180418.jpg
20220728_163944.jpg
 
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FluoFerret

Greasemonkey
Thread starter
Apr 2, 2018
184
43
Luxembourg
Can you take pictures of the pump drive on the torque converter and pictures of the flexplate? Also pics of the PCV system.

Here's a pic of the flexplate/converter holes. By the looks, I would bet my last cookies that the shop widened the holes for the bolts and did a sloppy job with a file/grinder or a drillbit.
20220821_170903.jpg
20220821_171001.jpg


here are pictures of the pump drive:
20220905_181136.jpg
20220905_181216.jpg


the PCV-system was another major screw up made by the shop:
right side a breather, left side a breather. engine splurted oil there, so they installed a pcv-valve on the right side that got hooked up to the carbs designated PCV-port. then the engine always ran to lean, and they just removed the breather on the right side, thus creating a permanent negative-pressure in the crank-case.
i redid it in april by hooking a breather right side, and a pcv-valve on the left with a hose going up to the carb-filter housing.
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
1,220
113
The converter was bound in the pump. It wasn’t floating. That’s the cause of your engine damage. And there’s probably metal in the trans too.
 
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