• Welcome to the Pontiac Trans Am Community, the Official Home of the PTA! Sign up for a (FREE) account today!

Crankshaft / Bearing Cap Totally Broke Apart

Brosain

Member
Joined
Aug 24, 2021
Messages
9
Reaction score
8
Points
3
Location
Orlando, FL
Hello All!

Quick story.

I've had my 78 T/A w/ the 400 for a little over a year.

It had been sitting for many years, so it barely ran.

After getting new fuel lines, tank, brake lines, carb, etc., installed, it ran great.

I was cruising down the interstate at around 65 when all of a sudden, the engine started knocking (I had plenty of fresh oil before I started my trip); then something major gave out, and it died.

Fast forward to today when I went by my engine builder's shop to drop off a check for a swap/rebuild, and he showed me what happened.

One of the bearing caps and crankshaft completely broke apart.

He said he's never seen anything like it before.

Is this a result of being ridden hard and put away wet for many years, and 45 years later, it decides to break on me?

Or is this a known design flaw?

Currently getting a Pontiac 455 installed with some extra goodies. :)

IMG_6907.jpg
IMG_6908.jpg
IMG_6909.jpg
IMG_6910.jpg
 

BillyMagg

New member
Joined
May 7, 2023
Messages
5
Reaction score
2
Points
3
Location
Central Obamastan
I know right?

I guess it was just my luck after 40+ years.

Had plenty of fresh oil and we were crusing down the highway at like 65 so idk.
It's not the time involved; it's more likely a poor casting and some load it wasn't designed for.

I would suspect improper torque at the last overhaul, possibly allowing the cap to loosen up, which allowed that cap to work a little bit.

Did your builder have any ideas after looking at all the pieces?
 

BillyMagg

New member
Joined
May 7, 2023
Messages
5
Reaction score
2
Points
3
Location
Central Obamastan
I know right?

I guess it was just my luck after 40+ years.

Had plenty of fresh oil and we were crusing down the highway at like 65 so idk.
My little black bird from before had a transplant 1974 GTO 350 engine, which on the hottest day of the year, with plenty of nice clean coolant and oil, died and did NOT want to start.

I suspected a broken ring and pulled the engine when I went to my builder; he found the #46 heads had a crack between the intake and exhaust valves.

So a simple head repair/replacement would have gotten me back on the road, but oh no, I had to blow it all out of proportion.

Good luck with your 455.
 

Brosain

Member
Joined
Aug 24, 2021
Messages
9
Reaction score
8
Points
3
Location
Orlando, FL
ny
It's not the time involved; it's more likely a poor casting and some load it wasn't designed for.

I would suspect improper torque at the last overhaul, possibly allowing the cap to loosen up, which allowed that cap to work a little bit.

Did your builder have any ideas after looking at all the pieces?
He just said that he's never seen anything like it. I'd only had it for a short time and drove it like grandpa, so I guess it decided, after my purchase, that this was the time to implode lol.
 
  • Like
Reactions: BillyMagg

Brosain

Member
Joined
Aug 24, 2021
Messages
9
Reaction score
8
Points
3
Location
Orlando, FL
My little black bird from before had a transplant 1974 GTO 350 engine, which on the hottest day of the year, with plenty of nice clean coolant and oil, died and did NOT want to start.

I suspected a broken ring and pulled the engine when I went to my builder; he found the #46 heads had a crack between the intake and exhaust valves.

So a simple head repair/replacement would have gotten me back on the road, but oh no, I had to blow it all out of proportion.

Good luck with your 455.
Thank you.

It's crazy how something slightly out of spec. can throw the whole shebang off.

I'm using one of the most reputable engine builders in Central FL, so hopefully I'll come out good on the other side.

Fingers crossed.
 
Last edited by a moderator:
  • Like
Reactions: BillyMagg

BillyMagg

New member
Joined
May 7, 2023
Messages
5
Reaction score
2
Points
3
Location
Central Obamastan
Thank you.

It's crazy how something slightly out of spec. can throw the whole shebang off.

I'm using one of the most reputable engine builders in Central FL, so hopefully I'll come out good on the other side.

Fingers crossed.
You'll be fine.

The's old cars have been around a while, and there is no telling the stories she could tell you if she could talk.
 
Last edited by a moderator:

Brosain

Member
Joined
Aug 24, 2021
Messages
9
Reaction score
8
Points
3
Location
Orlando, FL
You'll be fine.

The's old cars have been around a while, and there is no telling the stories she could tell you if she could talk.

Trust me, she's already talked to me, lol.

When I got the car I took out the seats etc and detailed the interior.

Cig butts were in every ashtray.

I'll let you take a look of what was under the front seat and yes, those are condoms I found under the back seats.

SMH

IMG_4786.jpg


IMG_4788.jpg


IMG_4755.jpg
 
Last edited by a moderator: