Yeah, the initial timing thing threw us too.  Anyway, long story short, I went the the local cam shop and asked for a more "modern" grind that would give me a little more HP.  What he gave me back was so far out of whack we can't imagine how the engine started in the first place. Only thing that comes to mind is when we were turning the distributor we must have found a small sweet spot that allowed the motor to start, never to be found again. Our heads came off with the cam tear out just to make sure there wasn't another problem, there wasn't. After dialing in the cam to see the numbers, Jeff was amazed with what he found. While the heads were off anyway, we decided to have hardened seats installed even though a leak down test showed we did a good job seating the valves in the first place. So I have two cams at the shop (same shop, there is no other) getting stock grinds, no more funny stuff. I'll post the numbers if you really want to see them.

Like Royce, I would like to know more details on the camshaft and exactly what you found wrong with it.  It strikes me odd that the engine initially cranked up and ran okay and now it’s not.  This makes it appear that the camshaft has changed timing at the timing gear set and/or has lobes going away.

Lorena, Texas (South of Waco)

What did you determine was the problem with the cam?  Is it a regrind of a stock cam?

Well...It's not the valves.  It's the cam shaft. The new grind is so far off that it's affecting everything.  There's only one cam shaft shop in the whole county so we're back to ground zero.  Ted, if you know of a shop that can repair our CS, please let me know.  Jeff has been checking around and we're not the only ones that are not happy.  Rosen down in Cali is backed up over a month due to covid.  In the mean time, we took the heads to a local  old timer that's going to put hardened seats in them.  Once we get a good cam shaft, I'm sure we'll be ready to go.

Leak down test coming this week. You're right, the cam is not too aggressive.  Gotta be dem damn valves.

All comments up to this point are valid.  I’ll add a couple more.
 
That slow turnover of the starter can be a result of a dragging starter.  Worn bushings in the starter can contribute to that.  Performing an amp load on the starter while turning over the engine could help to clarify that.
 
If the compression tester is old or has been used on a hot engine, it can be giving erroneous readings.  When getting abnormally low compression test readings, performing an accuracy check on the tester would provide some additional confidence in the readings.

Lorena, Texas (South of Waco)

To piggy back on Joe's comments  one thing you could try is to back off all the adjuster screws 1 or 2 turns and see what happens.. That would assure the hydraulic lifters are not bottoming out and holding the valves off the seat

20-21 inches of vacuum is a lot..  That cam must not be a big step up from stock..  It seems that compression now is your main issue.  I would start to maybe question your valve job.  I know my attempts at home brew valve jobs have not had great results.. Before you pull the heads i would invest 40 bucks in a leak down tester and zero in on were the compression leakage is happening..

Nothing in the inherent design of the Lincoln Y block would prevent use of a hotter cam... As long as you account for valve clearance at max lift with the block and pistons..   I have Lincolns where I run over .600 lift and 250 duration.. But accommodations have to be made for valve clearances..I doubt too aggressive of a cam is your problem

Good thought Joe, that's on our list. Fortunately there is a lot of play in the stock rocker arm adjustment.  Maybe this engine wasn't meant to have a more aggressive grind.

Did you check your rocker arm ratio and valve tip relationship?  With more lift, your longer pushrods may be bottoming out in those hydraulic lifters and holding the valves open a little when everything gets hot or heat soaked, losing compression.  I would think the stock pushrod would be more appropriate with more camshaft, not longer ones.  Joe-JDC

JDC