396 big block knock after warmup

[z28z11]

Beware of spun bearings in big blocks causing this kind of noise. I had a 402 do this, ran fine but knocked when warm, 2 spun bearings were the culprits. Loose torque converter bolts on another 402 before, too - loud "clank" on startup more than a knock. Better pull it down before it REALLY gets worse.

Regards,
Steve

[olddragracer]

On cars with an automatic transmission when checking for an unusual noise. The flex plate [flywheel] should be checked as a possible source. Remove the flywheel bottom cover and look up at the flex plate with a good light. Look for red rust leaking out of possible cracks. Sometimes cracks cannot be detected till the flex plate is removed. Noise from this part may only occur only when hot or only when cold. The noise can sound like a knock, a snap, a click, a clunk, or a rattle. It is the go to area to check when you have an unusual noise.

[1stgen68]

Thank you guys for all the info! Got up under the car today and quickly turned into a sissy to remove anything because the torq converter is really close to the flexplate and I can’t get a wrench up in there because of the space to try to tighten the bolts if loose so I gave up 1 man card put the dust shield back on and going to take it to a mechanic and explain where this knock is coming from.

[1stgen68]

Mechanic said torque converter and flexplate are fine. Also removed the fuel pump as well, still had the knock. He said that it's in tho motor even after i bet him 20 bucks it was the flexplate.
Now to find someone that can pull the motor and check basically everything and go straight down into the financial rabbit hole and come out butt hurt.

[68 Ragtop]

https://youtu.be/LONT1oboJrs

Is this your mechanic?

[1stgen68]

That was too funny man!!!! Geez i'm still laughing at that!!! I wish that was what the problem was!!

[1stgen68]

Turns out that I have to have the motor rebuilt

[JKZ27]

Sorry to hear, man.
Just curious, what was the failed component(s)?

[bcmiller]

Would like to know what they said was bad and pics of the items. Main bearings?

[1stgen68]

Oil pump was barely inside the oil pan. Crank was really marred everywhere. Cam was rounded off. Pistons looked like $hit. Hydrolic lifters cupped really bad. Lifters mushroomed out. Saw it today for the first time and was blown away with what I saw. Threw up in my mouth a little too.

[1stgen68]

Spun bearings charred beyond belief too. I didn’t take any close up pics. Sorry about that

[maroman]

Sounds like it really wasn't rebuilt or rebuilt poorly. Sorry for you! Fix it right then you will know and hopefully get some good from it.

[z28z11]

Amazing still that the engine ran with that much internal damage. Sounds like the builder didn't think much of oil pickup/screen clearances -

Regards,
Steve

[Kelley W King]

Did the car have an oil pressure gauge, factory.

[bcmiller]

In my opinion, the sounds captured in the video do not seem to match up with the damage found in the engine at tear down. But that is just my opinion.

BUT, I will tell you it is surprising how long a big block will run with damage.  A 427 WILL run with 3 rods shucked out the bottom end. And I mean OUT, like onto the road out. Obviously it didn't run well, and was only left to idle for a few seconds, but it did idle. Long story...