I almost had my engine buttoned up last fall but I had to put the project on hold over the winter, I left the exhaust ports on the cylinders bear with just some duct tape over them, but the clue unstuck itself and I just discovered that the ports have been open to air for the past few months at least

I also discovered that mice have been pooping around the engine compartment but they never made any nests that I could find. I've been killing them with traps and poison but obviously they are roaming around in there.
Can a mouse squeeze into a cylinder past an open valve? I'm wondering if I should scope the cylinders before I instal my headers? or is the gap of an open valve too small for even a mouse?
I definatly remember spraying oil in all the cylinders before taping over them so I'm not worried about rust but maybe dust?

 

It would be a pretty slender mouse to squeeze through a 0.480-ish inch "hot cam" valve opening. I've heard that bats can squeeze through an opening the size of a dime, or about 5/8", but that's a considerable difference compared to an open valve.

 

I bought a Honda Goldwing engine some years ago that was super low miles but supposedly "sitting stuck" for some transmission parts for a bike I was fixing . When I cracked open the engine I found the real reason it was stuck was from the mice that made a home in the one cylinder that was unfortunate enough to have stopped with it's exhaust valve open .

Is it likely ? Most likely not . But is it possible ? Hell yea , as my mouse **** rusted Gold Wing engine was .

 

About the best they could do is sling a turd in there.

 

Uh, helped a buddy rebuild a 70 454 SS Monte carlo that was sitting for over 20yrs.
Mouse went through the complete exhaust and made a nest in a cyl through a open valve. Almost had to sleeve that cyl due to the mess and rust...

 

Yes have seen it also, it was a big block chevy also. They must like rat motors.

 

I figured they'd like mouse motors.

 

They are some incredible little buggers, that's for sure.

 

Yea, probably best to get a scope camera in there and make sure they didn't squeeze in.
Thanks guys