427 broken valve spring

[HTM101]

Originally Posted by eschaider

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

Years ago I installed a Comp Cams camshaft, and a matched set of their recommended springs for that cam. About 5,000 miles later, catastrophe set in. The springs of #2 intake broke, the valve dropped, the piston slammed the valve which side-loaded the piston, which cracked the cylinder wall.

The 2nd photo shows the vertical crack in the cylinder wall at the 9 o'clock position that is allowing antifreeze to dribble in.

A very good set of springs costs maybe 5% of what I paid to rebuild that engine.