Who has heard the thin-walled cylinder 455 engine is prone to overheating.

That's a first I've ever heard this that problem (casting defect). Very interesting, I don't think I would have ever caught that one.

When I look back on the high-water temp problems I had, I think I can pinpoint it to the high compression pistons that the former owner had installed.

The Buick GS 455 was 100% restored in 2010. It had a Riveira 455 engine in it. The owner died, the owner's wife sold it back to the restorer around,
2011 or 2012. The restorer wanted the original matching numbers engine re-installed into the Buick GS.

The original GS 455 engine was sent out for rebuild in 2012.

3 years later (2015), the Buick was sold to RK Motors in Charlotte NC. Engine had 3 years of run time on it.

In 2015, Buick was sold to the former owner. In 2021 (6yrs later) I purchased the Buick from a Consignment Auto Dealership.

A friend of mind has a friend that lived close to this dealership. He drove the Buick and noticed he smelled either Race gas or Octane booster.
Also noticed the A/C compressor was slinging oil from its seal.

I contacted the owner of the Dealership and wanted the compressor replaced. He said no, so I offered a deduction of $4K on the car price and he accepted. As for the Race or Octane booster smell, I didn't think this would be a major problem thought maybe the distributor was advanced too far.

Make this story shorter, I had a borescope inserted down the spark plugs holes and took photos of the tops of the pistons.
We found them to be Race pistons. We then did a compression test, the specs turned out to be an average of 180 psi per cylinder.
I think this is higher than normal and most likely due to the high compression pistons.
We next did a Leak down test on the valves and found them to be in excellent condition.

With this good news, I decided NOT to do an engine rebuild, instead we went to an MSD ignition system with an adjustable vacuum canister.
Re-tuned the engine and its total advance and with all the changes we made to the coolant system and its parts, got the temps down to 180* with A/C off.

In summary, I believe the main problem that caused the high-water temps was the addition of the HP Pistons.
Maybe I'm wrong but it's the best I can figure out. The 3 years after the engine was rebuilt, 2012 to 2015, engine ran normal with a HD Buick copper/brass 4 core radiator. Just like the same radiator it came with from the Buick factory. Same 18-inch fan and same fan clutch.

It's amazing what will cause high water temps. I have built 2 high performance SBC engines and never experienced a high-water temps.
This was my first experience, and it took a while to solve this problem. VET

 

Hello Bens99gtp, I wanted to give you a attaboy for helping me with my high water temp problem.

If you have been keeping up with my posts on my water issue, you know I took your advise and installed Evans special coolant.
It helped along with all the other changes I made to my coolant system.
I just wanted to let you know that I appreciate your help.
There are many more members on this forum that have been a huge to me. Regards VET