Fwd: {Chrysler 300} Adjusting screw and nut ,hemi
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Fwd: {Chrysler 300} Adjusting screw and nut ,hemi





---------- Forwarded message ---------
From: John Grady <jkg@xxxxxxxxxxxxxxxxx>
Date: Mon, Feb 22, 2021 at 10:20 AM
Subject: Fwd: {Chrysler 300} Adjusting screw and nut ,hemi
To: Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>


A little more info learned on this; it turns out the thread on these is 1/2 -32, and the thread on adjustable  push rods (smith Bros--terrific source on any push rod)  is also 1/4-32; so 32 threads per inch gets us .03125 movement per full turn. This combined with the screwdriver slot on a 300 hemi adjuster (thought of as clock hands, as you view it ) allows rather accurate adjustment ; about  .0026 per "o clock" , say from two to three o clock. Tightening the nut moves it ,somewhat variable but on the order of .001

The adjusting screw itself is unbelievably hard steel  , while the nut is soft steel we think. So decided to make the nuts , but due to hardening , making the screw itself is  impossible with out complicated heat treat etc.. Related when measuring pushrods , the industry standard is radius of ball, not diameter .We measure diameter. Can cause very expensive confusion.  Most new solid lifters(comp ) are 5/16 ball socket, while the ball at top for our 300 rocker arms is an excellent 3/8 diameter. This comes up with new lifters , if the stock ones are shot. The lifter face if reused  should have a slight outward radius, never speckled looking flat or dished in. If you see that , the cam has issues too. And of course all has to go back is same hole 
There is a necked down area of adjusting screw to pass oil around the screw to the drilled oil holes in the rocker cup , that banded space has to align with oil feed hole within reason , or you have a dry push rod socket which will destroy itself.  This is  about right when about 5-6 threads of screw show above the nut , about .125". The oil feed hole center is about .138" down below top of rocker, but of course there is some variation. The slot is about .090 wide .

The easiest way by far to getting this right is to buy two adjustable push rods , under 10$  each, such that target length is is in center of adjusting range and right size balls , and adjusting screw is centered on oil band Mine centered on 10.08 and 11.5 , stock is about 11,  but new lifters also seem to have a different depth of socket in lifter , impacting all this . Then set and lock push rods , measure overall length with 12" caliper (worth having anyway--NEIKO good and reasonable on E bay) > Smith Bros push rods beautiful, one day turn around. 

I know may be dreaming but maybe a broken set of rockers sitting around in 300 land  with an adjusting  screw.....

John
May try to get a picture up , it is a cool design.....
---------- Forwarded message ---------
From: John Grady <jkg@xxxxxxxxxxxxxxxxx>
Date: Sun, Feb 21, 2021 at 6:28 PM
Subject: {Chrysler 300} Adjusting screw and nut ,hemi
To: Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>


So, working on 300D motor, one adjusting screw had been really murdered. Ball socket end had been damaged maybe by crossthreading , someone had tried to fix it with a grinder wrecked end. Even better , I think the screw is very hard steel, and the lock nut soft. So the same dude apparently crossed threaded the nut and drove it down on the screw anyway  cutting a new thread at an angle  in the nut  , but then it sits crooked against the rocker arm.. What I first noticed: There is no limit to past animalism in our cars at times .Despite wasting 30 minutes I could not catch screwed up thread end into rocker,-- rocker is ok, don't want to make things worse. 

So does anyone have a junker motor or left over partial rocker set etc, that has the screw and nut? 

Related< I posted a few weeks back about setting valves; jury is in ---you do have to use the Mopar sequence chart. Doing it at TDC on each cylinder results in about .002 error on intake valve..did both ways. So without further ado about it,use the chart.  Same 8 positions as needed both ways, cannot do two cyl at once.

Thanks for listening, 

John Grady 

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