Hello I have a 96 l31 that I'm planning to install into my k2500 today, but I have some concerns. Last night I was putting on the finishing touches before I take the thing of the engine stand, and while trying to find TDC to install my distributor I noticed something that worries me. Everywhere I could find said to put a finger over the #1 spark plug hole to feel for compression pushing against it as you rotate the crank. The problem is I don't feel anything. I can feel a slight bit of vaccume when the piston starts going back down but no audible hissing sounds like everyone is describing. I verified TDC by removing a valve cover but my question is with all new piston rings and the cylinder bores being freshly honed by a machinist should I be concerned with the fact the thing isn't blowing my finger off of the hole while spinning the crank with a ratchet? Any input is greatly appreciated!
Greetings katwood16,
When you installed the timing gears & chain, did you line up the timing marks per the manual?
We need accurate cam/crank phasing in order to generate proper compression.
And if that is known-good, we then need to verify how you adjusted your valvetrain. (Lifter preload?)
It's possible that if the valves are set 'too tight' that the held open valves will bleed off the compression
resulting in no joy.
At the same time, your observation about the 'vacuum when the piston starts going back down'
is a bit puzzling at this point. To me this makes cam phasing 51% probability vs too-tight valves
at 49%, but no matter what I'd want a brand new engine to push my thumb off the spark plug hole
with any speed on the ratchet. (Better test/easier to spin is all plugs out, instead of 7 plugs in and
turning over slowly. Much easier this way to 'feel' the compression stroke vs the other 3 cycles.)
Hope this helps. Let us know what you discover.