Should there be a rough rotation on crankshaft?

BLACK_MASK07

MEMBER
1986 GMC C2500
180,000 MILES

I noticed while trying to replace pushrod on 454ci. The crankshaft rotate bit stiff about 180 degree almost a full 360 degree. Not only that most of the hydraulic lifters aren't moving. Is that suppose to normal or is that telling me that my timing is off on my 454ci engine?

1 Reply

KENW1

MECHANIC
213 POSTS

Hello,

It may be due to the valve lash, if it is not within spec the valves will not open and cause it to turn hard. I would double check valve lash and also try it without the spark plugs in so there is not the compression resistance against you.

Below is the adjustment procedure, do not worry about the engine being warm part.

Valve Clearance: Adjustments
STATIC ADJUSTMENT

NOTE: This procedure does not apply to 231 V-6 engines.
1. Start engine and allow to reach normal operating temperature, then shut engine off.
2. With engine in position to fire No. 1 cylinder, adjust the following valves: V6-229 and 262,
Exhaust Nos. 1, 5 and 6; Intake Nos. 1, 2 and 3.
6-250 and 292, Exhaust Nos. 1, 3 and 5; Intake Nos. 1, 2 and 4. V8 engines, Exhaust Nos. 1, 3, 4
and 8; Intake Nos. 1, 2, 5 and 7. To properly adjust valves, tighten adjusting nut until all lash
is eliminated, then tighten nut the specified additional number of turns. On V8-454 / 7.4L engine,
tighten nut 3/4 additional turn from zero lash. On all others, tighten nut one full turn from zero
lash.
3. Turn crankshaft one complete revolution, which will bring engine in position to fire
cylinders 4(V6) or 6(Inline 6 and V8). With engine in this position, adjust the following valves:
V6-229 and 262, Exhaust Nos. 2, 3 and 4; Intake Nos. 4, 5 and 6. 6-250 and 292, Exhaust Nos. 2, 4
and 6; Intake Nos. 3, 5 and 6. V8 engines, Exhaust Nos. 2, 5, 6 and 7; Intake Nos. 3, 4, 6 and 8.
When zero lash is obtained, tighten adjusting nuts as specified in step 2.

ENGINE RUNNING ADJUSTMENT

NOTE: The following procedure, performed with the engine running, should be done only in case
readjustment is required.

1. After engine has been warmed to operating temperature, remove valve cover and install a new
valve cover gasket.
2. With engine running at idle speed, back off valve rocker arm nut until rocker arm starts to
clatter.
3. Turn rocker arm nut down slowly until the clatter just stops. This is the zero lash
position.
4. Turn nut down 1/4 additional turn and pause 10 seconds until engine runs smoothly. Repeat
additional 1/4 turns, pausing 10 seconds each time, until nut has been turned down the specified
number of turns from the zero lash position. This preload adjustment must be done slowly to
possibility of interference between the intake valve head and top of piston, which might
result in internal damage and/or bent pushrods. Noisy lifters should be replaced.