Need help and information for investigation of a low compression cylinder

vtos

Newbie
Hello!

I recently did a compression test on my buick 300. I got a decent 120# on all cylinders except the number 1 cylinder which read only 60# and it did not drop after sitting for 30 minutes.

Spark plug doesn't show any signs of mechanical damage nor any gas or oil on it.

I took the valve cover off and marked the pushrods and turned the engine over a few times and noticed one of the two pushrods wasn't spinning like it should.

Im thinking about pulling the pushrod to see if it is bent, and if it is, just replacing that to see where that gets me.

If I remove the whole rocker shaft.
Are those 4 bolts through holes where coolant could come out of???

Any other info yall might have would be greatly appreciated.
 

Attachments

  • 20220204_150050.jpg
    20220204_150050.jpg
    740.2 KB · Views: 4
If the push rod isn't spinning, neither is the lifter. That usually spells certain death for the bottom of the lifter and cam lobe. Not sure when they started using lifter and lobe crown to promote rotation. Nailhead engines did not?
 
Last edited:
Correct, the lifters are supposed to rotate even on "Nails" that were flat. But today the only lifters you can get for a "Nail" are like all the other lifters manufactured.
Unless that cylinder being affected has a very flat intake lobe & not passing any air at all the compression should be more than 60PSI.
Probably getting time for a rebuild as it is 57yrs. old unless it was rebuilt some time in the past.

Tom T.
 
Thank yous for all the info and help.

As for how due a rebuild is, I suspect the nylon type of timing gear to still be in place making me think it's not been opened up in quite some time
 
Back
Top