Re: 1941 One Eighty - curious engine problem

Posted by ineffabill On 2011/1/25 15:17:10

Reading this post gave me a wierd sense of deja vu - a 1941 180, misfire, except without the previous engine work. In my case #1 was dead - 0 compression. It turned out that the exhaust valve stems & guides were severely worn, letting the valve head "hang" off center & not close.
I did pull the head thru the fenderwell (that weren't no fun at all), but removed the fender completely when it was time to replace guides (& rings/rod bearings since I was in there.)
These big straight 8's have lots of mass & very low combustion pressure at idle, so it's not too unusual for a complete misfire to be overlooked until you put it under load.
After engine repairs, I found cranking compression tests to be around 70-80 psi. That's what you get with a 6.45 comp ratio. I assume psi will go up a little after seating the new rings.
In comparison, modern engines produce 150-220 psi compression- & won't run below 95 or so.