DIAGNOSIS:
LT5 Cam Timing
PROCEDURES:
Of note here, my engine is out of the engine bay and on an
engine stand. I will not go through every cam and the one
and six cylinder, just how to do one cam. The others the
method is the same.
Assumptions:
A. All cam sprocket bolts have been previously removed,
cleaned, and cam end threads cleaned.
B. The camshaft chain pretensioners are installed and
tightened "finger tight". Follow the manual for how to
properly tension them.
C. The reader here knows how to zero out a degree wheel and
what TDC (Top Dead Center) and MOP (Maximum Opening
Position) mean. It is assumed you have already zeroed out
the degree wheel.
D. The reader can set up a dial indicator on the lifter and
can determine where MOP is on a cam lobe.
E. Use the primary lobe for determining MOP.
Set factory timing:
1. Turn crank to crank locking position and lock crank
down.
2. Turn cams to factory pin position and use the camshaft
alignment timing pins to secure the cams in the factory
position.
3. Put the camshaft sprocket timing plate on the end of
the camshaft.
4. Pin the camshaft timing sprocket plate with the
camshaft sprocket pin.
5. Install the camshaft bolt and torque down the camshaft
bolt tight enough to hold the timing temporarily.
6. Remove camshaft alignment timing pins.
7. Remove crankshaft locking pin.
Verify cam timing:
8. Rotate engine clockwise.
9. Reading the dial indicator, determine where MOP is.
Here, we will assume approximately 114 degrees BTDC. Zero
out the dial indicator at that point.
10. Rotate the engine clockwise and observe the dial
indicator. When the dial indicator reaches approximately
.010 before MOP, verify the degrees on the degree wheel.
Let's say 131 degrees. Remember that number.
11. Continue to rotate the engine past MOP until the dial
indicator reaches .010 after MOP. Verify the degrees on the
degree wheel. Let's say, 97 degrees.
12. Add the two numbers, 131 + 97 = 228 / 2 = 114. This
is the degree that is set at the factory. Note, you may want
to review Marc's article for the factory settings for
particular year models.
To change a cam timing:
13. To change a setting, continue rotating the engine
clockwise until you've reached the previous degree setting
in step 10, above.
14. Loosen the cam sprocket bolt. Have one person holding
the opposite end of the cam keeping it from not moving. You
may not have to remove the bolt nor the camshaft sprocket
pin as there is play in the system.
15. If you need to change the timing to another degree,
say 112 degrees, BTDC, you need to rotate the cam counter
clockwise as you look at the cam from the front of the
engine.
16. Watching the dial indicator which is currently .010,
rotate the cam counter clockwise until the dial indicator
reads .012. This is an approximation so please note. There
is approximate .001 lift for each degree of cam timing. This
method keeps tension from the valve spring on the cam and it
cannot rotate around throwing off your timing. When you
rotate the cam, you do it from the rear of the cam. There is
a 19 mm, 6 point fitting there to allow you to either hold
or move the cam.
17. If you can't rotate the cam to this position, you
will need to remove the camshaft bolt, the camshaft sprocket
timing plate and the camshaft sprocket pin before rotating
the camshaft. Once the camshaft is rotated, replace the
camshaft sprocket timing plate, find an appropriate hole,
and replace the camshaft sprocket pin and camshaft bolt.
Reference Marc Haibeck's article.
18. While holding the rear of the cam in position as
verified by observing the dial indicator, torque down the
camshaft bolt to where it will not move. Care must be taken
to keep the dial indicator at the height you wish. This will
tell you if you have moved the cam a degree or so off. This
is very critical as there is play in the system and this is
your indicator that something has slipped.
If something does slip, just tighten the cam bolt down
and go back to step 8 and determine where you are now and
what needs to be done to change the timing to what you want.
Verify Timing:
19. Repeat steps 8-12 to verify the timing. If your
timing is off, go back to step 8 and proceed to determine
where the current MOP is on the timing wheel and set the
timing to what you want.
Final Torquing:
20. Once the timing has been set correctly, rotate the
engine back to the .010 before MOP on the dial indiactor.
21. Keeping the cam at the same position remove the cam
bolt and put Loctite 262 on the bolt. Replace the bolt back
into the cam.
22. Keeping a close eye on the dial indicator and making
sure the rear end of the cam is held tightly in one place as
not to change the dial indicator, torque the cam bolt to 20
ftlbs. Take a torque angle guage and torque the bolt to
between 80-85 degrees.
Verify Timing:
23. Repeat steps 8-12 to verify the timing.
24. Repeat steps 8-12 to verify the timing.
25. Once all cams have been timed, repeat steps 8-12 to
verify the timing for cylinders 1 and 6.
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