427 broken valve spring

[eschaider]

Originally Posted by Moriarty

I used the same parts as were used by the builder when the original owner had the engine was rebuilt in 1998. These: https://www.summitracing.com/parts/cca-928-16 (and yes, they are super stiff, but I assume what the custom cam is spec'd for).

Tonight, I took the valve cover off to check the valve train, and discovered the stud closest to the fourth cylinder had worked itself loose. Turns out, it is completely stripped. Not sure how I was able to torque it to spec when putting things back together - it must have been wedged well enough and then wiggled loose once the engine was running. I want to believe this is cause of the sounds. I've got a Time-Sert ordered to repair the threads, so I'll find out hopefully this weekend. Valve train itself still appears nice and straight.

Comp has sourced springs from various firms over the years. One of those firms was PAC. My engine uses a very different spring than yours does however a number of years ago I had problems breaking Comp springs. After I searched around for alternatives I settled on PAC.

As I explained the spring failure and source to the PAC representative he indicated that it sounded like a custom spring they had made for Comp. He also indicated that they did not recommend or offer that specific spring because of the specs the reseller had asked them to build the spring too.

I was steered to a nitrided spring with similar spring rate and a higher intake seat pressure, which I requested because of my higher than ambient manifold pressure. The springs have never failed.

I would be cautious of the spring choice you have made for your engine. PAC has several nitrided alternatives including behive designs that might be worth investigation. Despite the horrific appearance of your many broken spring pieces, you dodged a big bullet — the failure didn't kill your engine. The next one might ...


Ed