Last minute check on process for r/r R chain box and retiming cam

[911SCfanatic]

I have an 83SC 3.0L engine out for attending to the many oil leaks.

The last leak I am attending to is the right chain box. Before I dive in tomorrow, I wanted to do a last minute check so I am less likely to do something stupid. I couldn't find a post on the exact thing I was doing (engine fully assembled with a right chain box reseal), so I thought it best to risk getting chastised and just ask.

I have done searches, and will readily admit that I don't fully understand every aspect of timing. So, I will take some time and set the dial indicator up on the #4 intake spring and rotate the crank (CW) to get a feel for how the process should look. Since the 83 has cam bolt (vs. early cam nut), it sounds like I should use the method where, after rotating the crank to TDC, I remove the pin and rotate the crank (not cam) to get the proper overlap setting.

Regarding the chain box reseal, I was going to remove the components from the box, reseal the chain box (use ThreeBond 1104), and reinstall all components. I don't have a mechanical tensioner, so after I install the hydraulic tensioner (which I should prime first before reinstalling) I understand it will be difficult to maintain the chain taut (more so than if I were to do the left side). Any tips here?

Hopefully the cam won't have moved too much from where it was. All the rockers, etc. will still be in place, which I understand will maintain the cam somewhat in its original position. With the crank initially at TDC, I work through the timing process and triple, quadruple check until I think I have it timed properly.

Any subtleties missing? I am a bit nervous about this. TIA.

(By the way, what will happen if I used CurilT by mistake on the breather cover?)

[sww914]

You've got a pretty good handle on it, IMHO. The triple check part is good, maybe even quadruple check it. the CurilT isn't ideal on the brather cover gasket, but they don't tend to leak too much anyway, unless you put them on backwards.

[911SCfanatic]

Nothing else before I start tearing into it?

[304065]

I would pull off the port side chain cover and put another z-block on that with an indicator so you can see that both sides are timed the same. Rather than timing to the book value on the starboard side, you want them to match side to side.

Can you time the cam with all the rockers in place? Seems like it would tend to rotate the cam.

[Eagledriver]

When you say pull the pin and rotate the crank to get the proper overlap setting I don't understand what you mean. If you pull the pin and rotate the crank the cam will not turn and therefore the valve will not move.

If you haven't turned the crank or cam since undoing the cam sproket you will be within 10 degrees or so when you put the sproket back on. If you have turned either one you will need to check the other bank so as to get the one you are setting in the proper phase with the other side of the engine. If you install the cam 360 degrees off (one crankshaft revolution) then both sides of the engine will try to fire at once (your distributor will not support 2 spark plugs at once so that can't work).

It really helps to rotate the engine and see what the valves do and relate it to the four strokes of the engine and the firing order of the engine. Once you understand how it works the timing is much easier.

You would be wise to back off the valve adjuster screws on all the rocker arms on the side you are working on so you minimize the risk of driving the valves into the pistons. It can still happen but it's less likely. Just set the intake rocker for number 4 to factory spec clearance and leave the others full loose.

-Andy

[cgarr]

Bill, if you run into trouble, Denny and I are only a few hours away, you were there when I got in trouble so just give a shout..

[911SCfanatic]

Thanks, Craig, for the kind offer. Perhaps you can give some "remote" assistance.

I have rotated the crank about 50 times to get a feel for things, and I'm starting to understand a lot better. This is definitely a procedure that makes more sense as one practices it.

It has been about 20k miles since the last valve adjustment. So, I started with adjusting the valve on intake #1. I am timing the right side to the left side, and am checking to see how the "good" side was timed. First off, I noticed that there was no clearance between the adjustment screw and the valve stem, which is not unusual, right? I set the clearance to 0.1 mm. (I haven't bothered setting the clearance on the rest of them yet, though). Next, I set up the dial indicator making sure that the tip was on the flat of the spring retainer. I measured 1.31 mm from TDC to TDC. I checked it 10 times, and it still measured the same. My engine (930/16) is supposed to be 1.4-1.7, so I suppose I need to time the left cam as well as close to the target of 1.55 as possible.

After adjusting the valve clearance on #4 intake, the right side measured 1.27 mm. Seems like they were both close.

[911SCfanatic]

Andy, thanks for the tip on loosening the adjuster screws on the rest of the rockers.

[911SCfanatic]

The left side is timed to 1.52 mm, the right chain box has been replaced and resealed.
But, I can't seem to get the right cam timed...the chain keeps deflecting. (mechanical tensioners would be nice about now). Any tips?
I have to get this engine back in and the car on the road by noon on Wednesday!

[DSPTurtle]

Dont rotate the crank. Stick a small screwdriver through the cam chain sprocket and just rotate the cam. This shoudl keep the chain from being a factor as you are not adding or removing slack by moving the crank pulley.

[Eagledriver]

To keep the chain from going slack you can use a tool of some kind to jamb the idler arm against the chain. On one side I use a C-clamp. On the other side I use a 4 inch socket extension with a socket on it. I try different size sockets until the length is just right to jamb the idler arm tight against the chain.

-Andy

[911SCfanatic]

Thank you everyone for the help. Both cams are timed to 1.50 mm.

I definitely learned a lot. There's certainly some feel involved maintaining the cam timing when holding the sprocket and torquing the bolt. One odd thing I ran into: the sprocket would occasionally rotate the cam (w/ pin out) if I didn't have the bolt/washer installed hand tight. Only thing I could think of is that the sprocket was slightly cocked on the cam just enough to create an interference unless the bolt and washer was there?

Anyway, valves are adjusted and everything is going back together.