C7 Valve Lash Adjustment

[Kambaku]

I can't seem to find the information I need to work through the valve lash adjustment on my C7 CAT engine. From internet searches I have done, the procedure may be similar, if not the same, for the 3126 or perhaps earlier models in the FMTV class.

I have the adjustment sequence and the specs so that's not the issue, however, 2 things are confusing me.

1) finding top dead center (TDC) for #1 and #6 and...
2) turning over the engine manually so that I can accomplish the first step.

I think I can confirm TDC from the position of the intake and exhaust valves if #1 is actually at TDC, but I need to manually rotate the engine to do that. There is also suppose to be an indexing point(s) on the flywheel where you can insert the appropriately sized bolt into that I have yet to locate on the housing.

On cars and trucks that I have done in the past, all you had to do was put the appropriately sized socket on the big bolt/nut on the front of the engine and turn it over in the proper direction. However, my engine has a freewheeling fan clutch and not a visible bolt that I can see to grab on to. I saw in a TM that you are suppose to be able to turn over the engine by grabbing the alternator belt, SERIOUSLY? I obviously haven't tried this yet, but I can't imagine a big engine line this turning over that easily.

So...if this process has been described elsewhere on this great forum that someone's aware of I would appreciate someone pointing me in the right direction, however, for those of us who want to tackle this procedure, it would be nice to see a thorough documentation of the process which I will do if I can get beyond square 1.

Thx,

 

[Suprman]

I know nothing about the c7 or valve lash adjustment. But the fan clutch is kept off with air so if you drain the air system the fan clutch should be engaged.

 

[Kambaku]

UPDATE: Superman, you are correct re: fan clutch locking, however, since there is no bolt/nut to grab on to you cannot turn the engine over from the front of the fan; I checked that today.

However, I did discover that you actually can turn over the engine over by grabbing the alternator pulley. All you need to do is put a 1 3/16 socket on the front of the alternator and it turns everything over easily. The recommended rotation is CCW. I also located the timing holes in the flex plate. There are access bolts on both the left and right side. The one on the left side is difficult to get at, however, the bolt covering the hole on the right side of the flex plate is easy to get to from the top with the cab raised. You are suppose to be able to insert a 1.75" x m12 x 1.5 pitch bolt into that hole to index TDC. I have not gotten to this point yet.

I will provide updates on the process and my progress as this may benefit others in the future.

 

[Keith Knight]

When performing my transmission swap I turned the engine over both ways from the generator fully nut and by pulling or pushing on the fan. There is an access hole to the fly wheel passenger side, with the cab up facing the engine to the left of the turbo. To gain clear access to the threaded access hole which has a LARGE pipe plug in it that requires a 1/2 breaker bar to get it loose, I had to remove the exhaust and loosen the clamp holding the the 90 degree exhaust elbow to the turbo. The part that also has what looks like the exhaust brake on it and rotated that up out of the way to get to the hole. I needed access to the hole because thats where you gain access to the 6 bolts that attach the fly wheel to the engines flex plate. I did not see any marks but I wasn't looking for any either. You will need to people to do inspect it one person rotation the engine while the other persons looks for the mark in the hole. As I'm thinking more about it I highly doubt any markings would be on the flywheel because its attached to the transmission and the bolt pattern for mating to the engine is symmetrical but there may be a mark on the flex plate viewed from the access hole.