OK, I know how to find TDC on "Old school" engines, but what about the LS engines? I want to replace the rocker arms on my LS-7, and would prefer to follow the service manual procedure, but it does not say how to determine TDC. Any inputs would be helpful! Thanks

 

Take #1 spark plug out, rotate engine until compression is felt coming out of #1. Generally you can look in there with a light and watch for the piston nearing the top. On the compression stroke, both valves should not be moving (off the cam lobe). Taking more spark plugs out will help make it turn over easy.

You don't have to be exact but once you find near TDC on the compression stroke of #1, then from the Service Manual:

With the engine in the number 1 firing position, tighten the following valve rocker arm bolts:
Tighten exhaust valve rocker arm bolts 1, 2, 7, and 8 to 30 N·m (22 lb ft).

Tighten intake valve rocker arm bolts 1, 3, 4, and 5 to 30 N·m (22 lb ft).

Rotate the crankshaft 360 degrees.
Tighten the following valve rocker arm bolts:
Tighten exhaust valve rocker arm bolts 3, 4, 5, and 6 to 30 N·m (22 lb ft).

Tighten intake valve rocker arm bolts 2, 6, 7, and 8 to 30 N·m (22 lb ft).



Another safe way to do it is just do one at a time, 360 degrees of crank rotation off from where you saw that valve all the way open.

Have someone turning the crank, watch the valve stop when fully open, put a piece of tape on the crank and turn it 360 degs. That valve will then be on the base circle of the cam, remove the old rocker and torque on the new one.

Takes a while that way, but I like to be sure it's off the cam lobe. And 360 degrees from open is definately on the base circle.

 

I cannot tell a lie. I just torqued the bolts to 22 and went on. Nothing fell off that I know of and they seemed to work just fine, but yes, the method shown in post #2 is from the Helms manuals.

I'm so bad....


Elmer

 

Thanks. Whats the best way to rotate the engine? Braker bar on the crank bolt? Does it matter which way you rotate the engine? Thanks again.

 

I may do it the same way, but will try to install them in accordance with the service manual if I can. The service maunal has a pretty strong statement about following the correct procedure. Whats the possible problem with just cranking them all down to 22 ft/lbs? Could you possibly colapse a lifter?

 

clockwise as you look at it from the front. a 24mm socket cut down, half the distance of the inside of the socket

 

Great info.

 

Here is a little short cut for you. It's a pain to get down to the crank bolt sometimes. I put a wrench on the alternor nut and turn it there. If the belt is slipping which it will, put some extra tension on the belt tensioner.

Good luck
Randy

 

Thanks Randy, I'll try that