327ci mystery

Posted by Dan Marrin On 2019/6/10 13:30:00

The problem: My '48 Victoria convertible developed a rough idle in the summer of 2017 and I had an email conversation with Dave Czirr that fall, and we were unable to pinpoint the problem. I wasn't able to tinker with the car last summer, but now I am back on the trail in search of a solution. At that time I did an idle screw adjustment with a vacuum guage and was able to achieve only about a 16.5 reading. Manual says it should be in therange of 18-21. I attempted to pull the plug wires one at a time in an attempt to narrow down the problem and discovered that all of them had an effect on the idle performance except for #s 7&8. I am totally perplexed why those last two cylinders are apparently contributing nothing to the engine's performance.

Some additional information and things I tried at Dave's suggestions
*the timing is dead on
*compression test was fairly consistent #1-130, #2-123, #3=118, #4-130, #5-118, $6-110, #7-120, #8-128 (car was purchased from an elderly couple in Kansas, who claimed to have a valve job done before I bought it)
*tried blocking off the vacuum lines from both the electromatic clutch and the vacuum booster portion of the fuel pump and re-tested, but got same 16.5 reading.
*replaced all of the spark plugs
*tried squirting some oil along the interface of the intake manifold and the block adjacent to #7&8 to see if there was any improvement, thinking that the intake gasket might be leaking. There was no improvement, but I did re-torque all of the manifold connection for good measure

Dave and I ran out of things to try, so I am hoping someone here might be able to steer me in the right direction. I do have a video that illustrates the poor performance uploaded to my Dropbox, but am not sure how to make that available here?