Missing Exhaust Stud - Have you checked yours lately?
 

In another recent post, I described manifold pressure issues at high altitude (15k+).

During a thorough "going-over" of the engine, it was determined that one of the exhaust studs was missing on cylinder #1. :confused: I honestly can't say how long the stud has been missing, but it certainly would have a negative effect on manifold pressure at altitude.

It's as if the stud backed itself out and dropped off. It didn't break off. Its gone, as if it were never there.

The gasket appears in excellent condition. The plan at this point is to install a new stud using the double nut technique. Continental offers the stud in the original dimension, or oversized at +.003, +.006, +.009, +.012. I ordered the original and a +.003. We shall see what works best.

Next time you have the cowls off, check your exhaust studs. Grab your exhaust and try to move it a little. If you see any movement near the cylinders, you likely have a leak.

Exhaust leak could definitely lead to reduced pressure to the drive side of the turbo. Have run into this quite a bit on ground based turbo diesels.

Similar thing happened last year on my 182. Stud was just gone, not broken. Double nut technique worked. When I got my 337, a loose stud and exhaust leak overlooked by previous owner eroded the cylinder side irreparably and had to replace whole cylinder. I now keep attention to this area where exhaust manifold mates with cylinder.

Good to know about the oversized studs.

Thanks for sharing that. Sounds like it may be more common than I thought.

As you saw, a leak can cause damage to the cylinder head if left unchecked. Another reason to take a good look at your exhaust system periodically!