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Adjustment Procedure For Stud Mounted Rockers

  1. Remove the valve covers, and pick a cylinder you are going to set the valve lash on. Only do one cylinder at a time.

  2. Rotate the engine in its clockwise and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm.

  3. To adjust, back off the intake rocker arm adjusting nut and remove any tension from the push rod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the push rod seat up against the retaining lock, if you give it time to do so.  With solid liters there is no need to wait. 

  4. For hydraulic lifters, twist the intake push rod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the push rod, you are at "Zero Lash". Turn the adjusting nut down 1/2 turn from that point. Lock the poly-lock on the adjusting nut. For solid lifters, stick the proper size feeler gauge between the rocker arm and valve tip.  Tighten the rocker arm adjusting nut down maintaining the proper clearance.  The intake is now adjusted properly.

  5. Continue to turn the engine, watching that same intake valve/rocker you just set. It will go to full open and then begin to close. When begins to close, stop and adjust the exhaust rocker arm on that particular cylinder. Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.

 

 

 

Ford C4 exploded view (click image for larger view)

 

INCH TAP DRILL SIZES
Recommended tap drill sizes (for approx. 75% thread)


 

INCH SIZES - NATIONAL COARSE
----------------------------
TAP		DRILL
SIZE		SIZE
----------------------------
#1-64		#53 
#2-56 		#51 
#3-48 		5/64" 
#4-40 		#43 
#5-40 		#39 
#6-32 		#36 
#8-32 		#29 
#10-24 		#25 
#12-24 		#17 
1/4-20 		#7 
5/16-18 	F 
3/8-16 		5/16 
7/16-14		U 
1/2-13 		27/64 
9/16-12 	31/64 
5/8-11 		17/32 
3/4-10 		21/32 
7/8-9 		49/64 
1"-8 		7/8 
1-1/8-7 	63/64 
1-1/4-7 	1-7/64 
1-1/2-6 	1-11/32 
1-3/4-5 	1-35/64 
2"-4-1/2 	1-25/32
----------------------------
INCH SIZES - NATIONAL FINE
----------------------------
TAP		DRILL
SIZE 		SIZE
----------------------------
#0-80 		3/64" 
#1-72 		#53
#2-64 		#50
#3-56 		#46
#4-48 		#42
#5-44 		#37
#6-40 		#33
#8-36 		#29
#10-32 		#21
#12-28 		#15
1/4-28 		#3
5/16-24 	I
3/8-24 		Q
7/16-20 	W
1/2-20 		29/64
9/16-18 	33/64
5/8-18 		37/64
3/4-16 		11/16
7/8-14 		13/16
1"-14 		15/16
1-1/8-12 	1-3/64
1-1/4-12 	1-11/64
1-1/2-12 	1-27/64
1-3/4-12 	1-43/64
2"-12 		1-59/64
----------------------------
TAPER PIPE SIZES - NPT
----------------------------
TAP 		DRILL
SIZE 		SIZE
----------------------------
1/8-27 		R
1/4-18 		7/16
3/8-18 		37/64
1/2-14 		23/32
3/4-14 		59/64
1"-11-1/2 	1-5/32
1-1/4-11-1/2 	1-1/2
1-1/2-11-1/2 	1-47/64
2"-11-1/2	 2-7/32
2-1/2-8 	2-5/8
3"-8 		3-1/4
3-1/2-8 	3-3/4
4"-8 		4-1/4
----------------------------
STRAIGHT PIPE SIZES - NPS
----------------------------
TAP	 	DRILL
SIZE 		SIZE
----------------------------
1/8-27 		S
1/4-18 		29/64
3/8-18 		19/32
1/2-14 		47/64
3/4-14 		15/16
1"-11-1/2 	1-3/16
1-1/4-11-1/2 	1-33/64
1-1/2-11-1/2	1-3/4
2"-11-1/2	2-7/32
2-1/2-8 	2-21/32
3"-8 		3-9/32
3-1/2-8 	3-25/32
4"-8 		4-9/32
----------------------------


 


 

METRIC TAP DRILL SIZES
Recommended tap drill sizes (for approx. 75% thread)
 

METRIC COARSE SIZES
----------------------------
TAP                 DRILL
SIZE                SIZE
----------------------------
1mm x .25            .75mm
1.1 x .25            .85
1.2 x .25            .95
1.4 x .3            1.1
1.6 x .35           1.25
1.7 x .35           1.3
1.8 x .35           1.45
2 x .4              1.6
2.2 x .45           1.75
2.5 x .45           2.05
3 x .5              2.5
3.5 x .6            2.9
4 x .7              3.3
4.5 x .75           3.7
5 x .8              4.2
6 x 1               5
7 x 1               6
8 x 1.25            6.8
9 x 1.25            7.8
10 x 1.5            8.5
11 x 1.5            9.5
12 x 1.75           10.2
14 x 2              12
16 x 2              14
18 x 2.5            15.5
20 x 2.5            17.5
22 x 2.5            19.5
24 x 3              21
27 x 3              24
30 x 3.5            26.5
33 x 3.5            29.5
36 x 4              32
39 x 4              35
----------------------------
METRIC FINE SIZES
----------------------------
TAP                 DRILL
SIZE                SIZE
----------------------------
4 mm x .35          3.6mm
4 x .5              3.5
5 x .5              4.5
6 x .5              5.5
6 x .75             5.25
7 x .75             6.25
8 x .5              7
8 x .75             7.25
8 x 1               7.5
9 x 1               8
10 x .75            9.25
10 x 1              9
10 x 1.25           8.8 
11 x 1              10
12 x .75            11.25
12 x 1              11
12 x 1.5            10.5
14 x 1              13
14 x 1.25           12.8
14 x 1.5            12.5
16 x 1              15
16 x 1.5            14.5
18 x 1              17
18 x 2              16
20 x 1              19
20 x 1.5            18.5
20 x 2              18
22 x 1              21
22 x 1.5            20.5
22 x 2              20
24 x 1.5            22.5
24 x 2              22
26 x 1.5            24.5
27 x 1.5            25.5
27 x 2              25 
28 x 1.5            26.5
30 x 1.5            28.5
30 x 2              28
33 x 2              31
36 x 3              33
39 x 3              36
----------------------------



handy hint:

For Metric sizes only. Diameter of thread minus the pitch equals the tap drill size.
eg. M6 x 1
6 - 1 = 5mm

Calculating maximum RPM limits, by SteveW (steve'66)
 
    Why can a Ford 289 rev safely to over 7,000 rpm with the same stock 
components as a Ford 351 that will grenade well below that rpm?  The answer 
is based on piston speed.  In other words the rate at which the piston 
travels up and down the cylinder, measured in feet per minute.  At higher 
rpms, the piston travels from 0 to over 100 mph and back to 0 during each 
stroke.  The longer the stroke the faster the piston has to travel to cover 
the distance of its stroke during the engine's revolution.  If piston speed 
is higher than the limits of the crank, rods and pistons, the strain will 
result in failure.  
    
The formula for calculating piston speed is: STROKE times RPM divided by 6.  
 
As an example , a 289 has a 2.87" stroke.  To figure out the piston speed at 
7000 rpm, multiply 2.87 by 7000, then divide divide by 6.  The answer is 
3,348 feet per minute.  
 
A 351 has a 3.5" stroke.  And its piston speed at 7000 rpm is 4,083 feet per 
minute.
 
The pistons in the 351 will be travelling 735 feet per minute faster than the 
289 at 7000 rpm.  Creating much more load stress, and in this case failure. 
 
 
The following maximum piston speeds are from the book, Performance Tuning in 
Theory and Practice, by A.G.Bell.  
 
Stock  Motor       -       3,500 fpm       (cast crank, stock rods and cast 
piston)
Heavy Duty Motor  -     4,000 fpm       (forged crank, peened rods w/ good 
bolts, forged piston) 
Drag Racing Motor -     5,000 fpm   (forged crank, alum rods, lighweight 
pistons, etc.)
 
 
Different "stock" Ford engines have different maximum rpms based on piston 
speed:
289     -   7,317 rpm max
302/5.0 -   7,000 rpm
351     -   6,000 rpm
390     -   5,556 rpm
400     -   5,250 rpm
428       - 5,276 rpm
460       - 5,455 rpm
(Some high performance "stock" engines have forged cranks and pistons and 
could survive higher rpms than listed above, use the heavy duty formula for 
those engines)
 
The formula for determing an engine's maximum rpm is:
 
Stock  - 21,000 divided by the stroke
H.D.  -   24,000 divided by the stroke
Race  -   30,000 divided by the stroke