Hey all,

Want to confirm what might be happening. The heads have about 1 hour road time on them since a rebuild. Exhaust primary #3 is always 200 F hotter than the rest of the primaries as measured externally with an IR gun. I switched injectors and no change and also did a lifter preload adjustment to 1/8 turn from 3/4 turn with no luck. I hear a hiss at this cylinder when the engine is off and I still get a primary that is hot.

I assume it is the exhaust and conclude that the exhaust gasses are escaping during the combustion process and hence the higher primary temp.

I am going to get a stethescope here today and also do a compression test. Leak down test would have to be done by someone else as I don't have that level of equipment.

What are some people's thoughts on what is going on and do I let this keep going or correct it by taking the head off and having it looked at?

Power is good and it runs fine otherwise.

Ben

 

How about a leaking injector that drips a small amount of fuel? If the engine was hot, the fuel would expand and might make some noise. It would also run that cylinder rich and might account for the higher exhaust temps.

Pull the rail up out of the manifold and pressurize it by cycling the key to the on position. Look closely at that injector.

It's wild stab in the dark, but I've come up with wilder things.

 

He already changed the injector.

Also running richer would tend to run cooler not hotter.

The only recommended test be done is a leak down test. I believe the exhaust valve in question is not fully closing. If you find that to be the case with a LD test, remove the rocker completely and rerun the test. If it still leaks, you will have to remove the head.