Exhaust Gasket Failure - Story

[MoonlightVFR]

This is a story of exhaust gasket failure.

I was cross country St Louis to Memphis tracking the Farmington VOR. Cruising at 4500 ft on a beautiful, beautiful spring day.

Air was so so smooth at 4500 ft. Engine running smoothly. Oh, I was so happy, very happy engine had a MOH few hundred hours.


Then it happened. I heard and felt an explosion. Engine did not miss a beat it was still a happy engine. Yes I felt the explosion. I could feel the concussion of the explosion ripple down along the right side of the airplane fuselage.

I did not have a clue, still pretty green at airplane ownership. I was startled . Engine was still running smooth, not any extraneous sounds.

I contacted Center and modified my flight plan. Told them what had happened and was now going to track HWY 55 South down to Memphis. Precautionary Landing on highway if necessary.

Landed, looked under the cowl everything looked good to my inexperienced eye.

Return trip to St Louis, 1 hour out of Memphis, explosion again rippled concussion along right side. OK something is not right and this plane is going in to the shop.
My A/P John Staples found the cause. Exhaust gasket failure. He pointed out that the design of the intake manifold is right next to the exhaust. I do not like this 1920's design used in the C-145 engine ; Intake port . exhaust port - CLOSE is not the word they are decidedly adjacent.

John stated that when the gasket departed this allowed direct hot exhaust to contact the intake manifold and it detonated fuel air mixture PRIOR to entering the cylinder. He further stated that I was fortunate , he said I could have lost a cylinder in flight and it would have deteriorated even further.

Realize this is happening when cooling air is moving into cowl at over 100 mph.

Years later another A/P stated that it was not just direct hot exhaust; he stated that there were Flames from exhaust directed at the intake post. I want each fellow pilot to think about that. Direct flames. He stated that he has fired up uncowled engines at night and can see slight flames from good joints.

The exhaust port is so close to the intake port that Bill Clinton could not get one of his skinny fingers between the two.

Insist on good exhaust gaskets and proper installation technique.

[blueldr]

A conversion to the Continental IO-360 is the answer. And, if you can do most of the work yourself, it will only cost about $25,000.00. But keep in mind that it will be one helluva C-170.