07/15/2026
These are brand-new cylinder heads. During inspection, we found valve guide clearances as high as .0045”—completely unacceptable for a performance street engine.
We sent the heads back to the manufacturer and were told our measurements were wrong. After getting them back, I personally rechecked every guide, verified our measuring equipment, and compared multiple other heads and valves in the shop.
Our measurements were right.
So now I’m filming the inspection process to show the manufacturer exactly what we found.
Could I simply replace the guides, perform a valve job, and charge my customer? Sure.
But why should my customer pay to fix brand-new parts?
This is the reality of the performance industry today. We’re spending more time than ever documenting defects, proving our measurements, dealing with warranty claims, and fighting manufacturers over quality issues—all work that’s difficult, if not impossible, to get paid for.
It’s also one of the biggest reasons projects take longer today than they did just a few years ago.
Until manufacturers start taking quality control seriously again, we’ll keep doing what we’ve always done: checking everything. Because “brand new” simply doesn’t mean what it used to.
👉 www.siebertperformance.com
