When I experimented with this jack bolt idea, I was in the middle of preparing and installing my stage II head.  I prepped the stage II head for the jack bolt too.  Instead of a 3/8-NF jack bolt I set it up for a 5/16-NF and incorporated a steel threaded bushing in the aluminum head (for durability).   But I wasn’t ready to try it yet, so I plugged the jack bolt hole and put the idea on the back burner.

At that time, I was concerned about making the cam chain drive too rigid.  Although the factory design seems to lock the tensioner in place, that long rear guide is still flexible.  Once I put that jack bolt in there, the rear guide becomes rigid.  So, when the cylinder grows, the pawl restrains the bottom, the jack bolt restrains the middle, and the pivot bolt restrains the top.  It’s not gonna give much.  We already have a problem with accelerated chain wear.  I wasn’t willing to solidify the system.

Later, I start seeing discussion on the forum about Batman’s complete removal of the tensioner pawl, and then Dave sets his up with no pawl and a stopper to restrict plunger retraction to 1mm.

While I understand that Batman’s system is working fine, I need more control over my valvetrain.  The unrestrained plunger setup is fine for a daily driver, but I’m pushing mine past 6.5K on a regular basis, and I’m fixin to bring the valves a whole lot closer to the piston.
 
With the pawl removed, you can watch that plunger stroke in and out a bunch as the engine rotates.   Every time the intake lobe goes past the nose, the valve springs take control and drive the cam.  That takes the slack out of the rear side of the chain.  The pawl is there to prevent the cam from running away.  The cam lobe has a deceleration ramp that is intended to gently place the valve on the seat.  The deceleration ramp can’t perform its intended function if the rear side of the chain is slack.  The chain must hold back the cam as the intake valve is closing.  

Dave’s setup (no pawl, stop to limit back travel) limits the slack on the rear side of the chain.  I can use a tensioner with the pawl removed, incorporate a stop to limit plunger retraction, and install the jack bolt to take up the majority of the excess slack.  

Instead of extending the front side of the tensioner plunger (like Verslagen), I extended the back side 15mm.  That provides additional engagement with the tensioner bore to keep the plunger straight and prevent cocking.  I left off the rack for the pawl (I could never machine that) so the plunger has a nice close fit completely around it’s circumference.  It’s very stable.

Here’s the finished tensioner installation with jack bolt adjusted for 18mm plunger extension.  Almost all the plunger shaft is engaged with the tensioner housing.

It looks like all the big problems have been addressed.  Lob off the cylinder .130” to reduce quench to .060” and increase CR to 10.4:1.  Provide adequate clearance between valves and piston by machining valve reliefs .130” deep in the top of the piston.  Remove excess slack from the cam chain using the special jack bolt and extended tensioner plunger.   Correct cam timing by advancing the drive gear one-spline.

Machining that cylinder was quite a project on my teeny-weeny Chinese lathe.

When all the machining was done, it had to be assembled with gaskets and torqued to spec in order to verify correct quench.  Quench was checked by laying feeler gages on top of the piston and then laying a strip of lead wire on the feelers.  Rotate the engine through several times, remove the head, and measure the thickness of the crushed lead wire and feelers.  The total thickness of the feelers and lead wire was .0595”.  Close enough.

Prior to machining the cylinder deck, the oil feed groove for the cylinder head must be made deeper.  The stock groove is only about 1/8” deep.  Since I was removing slightly over 1/8”, the groove would be eliminated.   I used a die grinder to make the groove ¼” deep.  That way, once I was finished machining the deck, the remaining groove would be about 1/8” deep.

You stick the bit down through the clay until it hits the aluminum, then gently run the plastic tube down until it just touches the clay.  Pull the assembly out without disturbing the tubing.  Now you can measure how thick the clay is.