What would cause a broken valve spring? 454 vortec

[DONWATERS]

I bought a 97 suburban, 454 vortec 159k miles. It had a broken valve spring. PO changed the spring but the valve had dropped enough to hit the piston and bend, so no compression on that cylinder. I bought it so I would have a spare engine for my truck, since they are hard to find even as cores.

What would cause this? The engine is real clean inside, no sludge but this is due to the factory rochester injectors leaking, like mine did. It is a low lift roller cam, not a lot of stress on anything. And the springs have rotators. It was an exhaust valve, number 6 cylinder.

I am a little worried. My truck has almost the same mileage, and if it happens on the road its a tow and a lot of labor. I just had to swap the cam out of mine due to it going flat, which was absurd.

 

[spasm3]

I'm guessing over-revving in park or neutral and floated the valve.

 

[rubberchicken]

Come on up to Maryland and buy my 97 Suburban, 454 4x4 4.10 gears, 105k miles. Engine runs perfect but might need an idle air control valve. Has broken brake line, and top surfaces very rusty. You might want to restore it, or use it as a donor vehicle.

 

[BrocLuno]

Weak and tired GM springs (they often fail testing when well used) and holding it in low gear while pulling hard or climbing ...

I would not put GM springs back in it. I'd get the heads done and I'd go with Howard's, and rest easy

The bottom end should be fine. They are very durable

I have never seen or heard of a 454 pushing a crank out the bottom - even racing. Yeah, rods can go. But usually sideways. These are really tough engines, except for the valve gear ...

 

[clinebarger]

Valve springs break on engines with heavy valvetrains.

 

[joegreen]

i know that spring manufacturers are pretty specific on there being not surface rust or nicks or anything on the spring as it can be a stress riser and cause the spring to break. Even if the spring was dropped on the floor it should always be inspected.

 

[DoubleWasp]

Absolutely nothing besides being a GM 454. Heavy valvetrain and mediocre springs.

In the industrial engine books by manufacturers who use GM engines to run equipment, it is always suggested to replace the GM valve springs with "racing units" for sustained engine speeds in the upper rpm range before entering a brand new engine into service.

Small block springs float. Big block springs just up and break.

Pull the head and have a competent shop rebuild it with good valves, and something like Comp springs, or Comps themselves. Then use the same high performance springs on the other cylinder head as well and spare yourself future troubles.

We have to do this for boats aaallllllll of the time. When we do a new engine, we always ditch the factory springs and rockers.

 

[demarpaint]

They occasionally break, it happens. I had a broken valve spring on a Chevy 250 I6, which was everything but a high power, high performance engine. Driving along one day, and it broke. The good news was it was an easy diagnosis and fix.

 

[daman]

Over revving my guess, my 99 454 has 203,000 all stock no issues, I did swap out the factory leaking injectors for mustang 5.0 ones since then it's been like new puuurs and pulls no problem.