mark928gt

After a bit of a hiatus I'm back at my engine rebuild. I think I have the time to actually complete it this time.

I have the heads installed (rebuilt by Greg Brown), cams in, new cam chains, new wear pads, cams set properly and everything torqued. The crank is sitting at 45 degrees. I then went to rotate the cams to get them set at TDC. I was reviewing Dwayne's posts on TB replacement and he mentioned to rotate the cams with the 17mm bolt on the front of the cam gear. I was trying this and got concerned that it was too hard and that something could possibly be wrong.

This is where I stopped and started searching the forum. I couldn't find anything that mentioned how much force this should take to rotate.

Is the 17mm bolt the best way to rotate the cams and should they take quite a bit of force to move? I was concerned I might strip the threads on the 17mm bolt, or worse yet...

I imagine it should take a lot of force if I have to compress all of the valve springs.

Thanks for the help.

Mark

17prospective buyer

They will buck as the lobes open the valves, you should feel push back as you're turning for about 90 degrees of rotation, then as a particular cylinder reaches TDC powerstroke, the lobes in question are on the upturn or closing ramp and should spring the cam clockwise. Are the valve covers still off or did you put them on?

Does it just hit a dead spot as you rotate it or is the resistance more or less linear?

mark928gt

Hey Matt,

The valve covers are still off, there is no belt on yet and no plugs in. I actually haven't rotated it at all yet. The amount of force I was applying to that 17mm bolt was concerning to me.

That's when I decided to ask the forum question about whether continuing to torque on this bolt was correct. I am tempted to next put a wrench on the 30mm hex washer behind the 17mm bolt and see if things turn. At least I'm not continuing to stress the threads.

17prospective buyer

I believe that is the correct way to turn them, with the hex washer. How long of a tool were you using? That'll effect perceived effort/torque alot. You can also turn them with the wrench flats cast into the middle of each cam, though it isn't really the best way. You torqued the cam caps down as evenly as possible? Tensioner is in correctly? Springs back? Rotor and the Hall effect wheel/plate are on behind the cam gear?

GregBBRD

Turning the cams with the 17mm bolt will over torque the bolt. The 30mm hex is for this. As long as the engine is at 45 degrees before TDC (and the damper is installed correctly), the valves can not hit the pistons.

OTR18WHEELER

Last year Rod Underwood had the same issue one cam that seemed to be stuck. He eventually discovered that one of the caps was put on backwards. That's all it was.
Have you loosened the caps and tried to turn the cam? It's possible one, or even more caps are not in the correct location or position.

Leon Speed

The cams themselves have a (17? 19? 21? mm) hex profile on them. Of the cam covers are off, you can use those to turn the cam.

Mrmerlin

before you turn anything please post pictures of the cams installed and the caps.
The cams should only be turned with the 30 mm washers.
Note using a 30 mm wrench works well for this.
Note put some oil onto the cam lobes and let it run into the tappets before you attempt to turn the the cams.
Note you should have also put assembly lube onto the caps of the cams.

The damper should be able to be read while facing the engine,
if the numbers look upside down then the damper is on backwards.

Please take a picture of the crank damper as well

Vilhuer

Some people have managed to put them wrong way round and run the engine. This will very likely wear out cap and cam bearing surface.

I think its bigger than that, maybe 24mm. In any case I always use that when covers are off. Just have to remember to watch out where cams want to go when valve springs push them.

mark928gt

Ok. Here are some pics of the cams installed and the damper sitting at 45 degrees. I don't see any caps that are installed backwards and I tried to be very careful to make sure everything went back in the exact place it came out of. I put high pressure assembly lube on the top of each lifter but not necessarily on each cam lobe.

Dave928S

It's 28mm.

Vilhuer

All intake cam caps are all backwards. Do not try to turn cams before you change them around.

Vilhuer

More likely it should be 27mm but some dimensions are little on large side.

Ed Scherer

Yup. Here's some photos of my '90 S4:

Right side:



Left side:

Vilhuer

Turn them around one at the time. That way you will not cause more problems.