Variable hydraulic lifters for 440 engine
This shitty vacuum did not come because i had the engine opened up, even with the severely advanced cam setup it suffered the same.
And now confirming the engine runs without load caused by the tranny it remains low.
It must be the nature of the beast i guess, this cam in a 440 BB.
with the cam advanced 14*, it should have had a much much higher idle vacuum.
That it didn't, I think, is pointing us to something else. Low manifold vacuum, in a performance engine, with no vacuum leaks; is caused almost exclusively by the late-closing intake valve.
One cam I had,the 292/292/108, ran so "poorly",that I was desperate to know when the intake valve closed. What I did was install a timing tape on the damper, then put the piston at the bottom of the intake stroke. Next I injected air into the plug-hole regulated to 30 psi, and continued to rotate the crank,in the normal direction,until the bar I was using, began to bounce in my hand, as I tried to continue.
With a 4" piston, 30 psi is 377 ftlbs of force, so my 20" bar and me were not heavy enough to control the bar, as the cylinder began to build pressure. I reduced the pressure, and put a pipe on my bar, until I could find the threshold within a few degrees, of when exactly the valve closed, and the cylinder began to be pressurized. What I found was that the piston in terms of degrees was actually about half way back up the bore, when compression began.
When you "time/degree" a cam, this is the thing you are moving; the intake closing angle. Yes, of course, all the other points are simultaneously moving, but the Ica is the only one we are usually concerned about.
So that is when I put 2 and 2 together, why my intake vacuum was so low.
However,in my case, I didn't believe that it was the only reason. I eventually traced a portion of my problem to another source, fixed it, and then I had a monster-engine. It still idled "poorly", but it would idle a whole bunch slower and was much happier about it.
