Has anyone modified or heard of modifying the Mercruiser 496 cast iron exhaust manifolds to add EGT sensors? It seems like it might be possible to drill and tap in the lower section which appears to be under the water jacket area of the manifold.

I'd like to add a reliable way to monitor for potential AFR issues. I have added bungs to the riser elbows (thanks to Eddie Young for the idea!) but the O2 sensors don't seem to last very long, presumably due to moisture making its way back to that area of the riser at idle. I also can't monitor for individual cylinders running hot that might not show up in the average AFR reading at the elbow.

Wanted to get other's thoughts on the idea - good/bad? Useful / not useful? I appreciate any input!

You need one of these:
https://www.innovatemotorsports.com/...fA1iqzT4AkotZQ

They must be clocked correctly. You might have to buy shims from McMaster-Carr get it perfect. I ruined several sensors over the years, not
a single failure in roughly 100 hours run time after installing the HBX-1.

Steve

Thanks! I'll definitely look into those. Appreciate the tip on the shims, one would think that would come along from the manufacturer!