Cam Timing, Please help.

[LeakProof]

Guys, guys, guys!

I'm getting nuts already!

Left side:
Put welders vice grips on the idler arm with LOTS of tension on chain!
Could barely lift it off the ramp. (good so far)
Timed it to a perfect 1.0 mm.
Removed vice grips.
Installed carrera tensioner.
Torqued to 150 nm.
Checked timing.
This time it reads 1.21
Should I ignore this?
When engines running, will it go back in to spec?
When the tensioner has oil going to it will it then bring me in to spec?
Should I prime the tensioner in oil, will it have more tension?
Maybe I should set both to 1.1 with carrera tensioners only?
The Service Manual shows the timing being done with the carrera tensioners installed & nothing else to increase the tension.
Any input would be highly appreciated.

Thanks,

Leakproof.

[edgarcia737]

Do you have Wayne's 911 engine rebuilding guide? It's the best step by step reference I've seen. With new tensioners, you need to submerge in motor oil. Remember, the tensioner needs oil pressure to work.

My advise, get Wayne's 911 Engine Rebuilding book. I'm on the road right now and don't have access to my book.

Ed Garcia
480-200-5778
1977 Carrera 3.0

[lindy 911]

When you timed the cam, did you then rotate the crank at least eight times and check the dial again? This is an important stage of the process as it makes sure that the crank sprocket is pulling the cam sprocket without any slop in the system. Make sure you don't overdo the tension with the vise grips. You want it good and snug but not so tight that things bind up.

Loosen the death grip on the vise grip a little, set the cam, rotate the crank at least eight times and then check the dial. The reason the crank rotation is important is that all the moving parts are allowed to line up with each other.

Keep your chin up, you'll get it.

Lindy

[LeakProof]

Ed,
I do have Wayne's re-build book, plus other's, and know it like the back of my hand.
But timing is one of those things that appear to have a gray area, A feel, example: the valve clearance gap, the alternative method proves this.
That can't necessarily be explained in books. It has to be taught to you from people who know. Kinda of like the trade's, book's and class only gets you so far.

Lindy,

I did not rotate 8 times, I will try that now.
Also I have a feeling, my death grip was possibly to tight with the vice grips.
It was actually kinda hard to turn over, perhaps a little binding like you suggest.
Perhaps a combination of turning over 8 times and loosening up the vice grip's will do the trick.
I wonder if re-priming the tensioner's would play in to this, I'm actually closing the tensioner almost by hand. All the oil's been squeezed out already.
For somthing so precise, this seems to have a lot of gray area.
Thanks,

Leakproof.

[lindy 911]

It is easy to over think this process and get into a situation of uncertainty. When that happens, take a step back, clear your head and start back with the basics.

The idea of tension on the idler is to get rid of any slack in the chain; that's it. Instead of vise grips, I use a pair of channel locks. I grab the idler arm and pinch it to the top of the case just like with a pair of vise grips. Once I have it there I wrap a good zip tie around the handles and pull it snug. That's all the tension required, no more. Wrap some masking tape around the jaws of the channel locks to protect the idler and the chain box.

Every thing you do with the cams and timing should be very smooth and easy. There should be no extra effort needed to turn things or make things fit. It should all go together easily; if not, stop, back up and find out why. If you take your time it will be evident what's not right.

Make sure you only have the intake rocker for #1 in place. If you try this with the other rockers installed, the spring tension from the other valves make the process much more difficult.

Lindy

[jimbauman]

...and don't forget, you have a target range of about .3 mm (.15mm either way of perfect).

JB

[edgarcia737]

I hear you. But like jimbauman says "you have a target range of about .3mm". Keep us posted. I remember the first time I did the cam timing. But I took my time and networked, just like what you are doing. If you lived a little closer, I'd just come over and show you.

take care,
1977 Carrera 3.0

[dtw]

The chains just need to be snugged up, not so tight you can't lift them. Having read a few of your posts about your rebuild, can I offer a couple suggestions:
-Ease up the tension just a bit on the chains. If you get a .2mm variance between timing with vice grips, and then with installed PFTs, and it is on any CIS cams, and still within the book range, then move on with a clear conscience.

-Go back and check your cams' woodruff keys. The installation method you mentioned is the best way I can think of to trap the key between the cam and the alignment sprocket, without actually seating the key. Maybe you nailed it....but what if you didn't? You didn't see the keys seated, so you can't sleep w/a clear conscience.

-Most motors have 4 & 3 cam sprocket shims. Never seen 4 & 4. That's not to say yours is wrong - however - even if you had had 4 & 3, sprocket alignment should be checked. It is easy and quick, and there's no reason not to do it. There's every reason TO do it. This should be done, of course, AFTER verifying the proper seating of your woodruff keys.

-The tightness in turning your engine is a concern. I assume at this point you've only got a maximum of 4 rockers installed (1I, 1E, 4I, 4E) and no spark plugs? If so, an aluminum 911 motor with CIS cams, 4 rockers, and no plugs should turn over pretty easily. Why isn't yours? First, back off the tension on your vice grips - hopefully that is all it takes to fix the situation. If not...time for further exploration.

All of this may sound really nitpicky. Now that I've been through several rebuilds, I'm finding that just assembling a 911 engine is easy. What it takes to make a smooth, leak-free, and strong motor is all in the details. Take the time, it is well worth it!

[304065]

Green= power, Gray= exhaust, Blue= intake, Red= Compression.

[LeakProof]

Thanks for all the technical support guy's.

Yea, I think I started to over think this for sure. Starting over with a clear head sure helps.

Only two rocker arms installed, #1-I and #4-I, thats all. Also no spark plug's in.

As soon as I let up on the tension, things got a lot better.

Turns over like butter, no issue there.

This time I'm, definitely confident that I got it.

1.0, both sides with tension. And 1.06 with primed carrera tensioner's installed. Apply slight tension to the (idler arms), and wala, 1.0 both sides.

I'm gonna run with this. Also moved each key one hole, so I'm glad I addressed this for the third time.

You guy's are correct, this is a very smooth process, and not to difficult.

What I don't fully understand is, why not skip the tension part all togather, and just set it to the 1.06, knowing it will bounce back when the engine is running and chains are tight. Oh well I'm not going to question the method, just happy it's doooone!

Oh, I checked the woodruff keys and there seated, real good.

Now, I will start installing the remaining rockers.

You guy's are all terrific for sharing your time and knowledge.

Thanks again.

Leakproof, Mike.

[dtw]

Sounding really good! Great job!

I think tasks like tensioning the chains are really subjective and difficult to convey in media like Wayne's book. It just takes some experience and getting a 'feel' for it. My first go-round was nervewracking. The cams were high-lift, high-duration, and my piston/cylinder clearance was on the ragged edge, so a little movement was cause for concern. It all worked out fine in the end. Since then, with more builds under the bridge, I now encounter negligible difference between cam timing during the build with race tensioners, and subsequent measurement with PFTs.

Measure your sprocket depth and you're good to go

[Flat6pac]

If the sprocket depth isnt right youre back to square one, that should have been done and measured before you put the key in.
You measure depth each time you build an engine because if you believe what is there youre depending on the quality of the previous builder.
Bruce

[Walt Fricke]

Bravo

What did the chain wheels look like on this engine? If the teeth were all worn on the sides, it might be that the parallelism (those shims) was off. If they all looked good, maybe it was fine despite the slightly non-standard shim count.

Bruce is right about checking, if you don't know that was done on the previous rebuild. Wayne's book explains it. But you should enlist a friend to help, either to hold your straight edge while you measure, or vice versa. Unless you have a buddy who has the straightedge holding tool.

Remember an earlier post, where someone said to tighten the big nut 3/4 tight? It is after that that you turn the engine over several more times, just to check your timing setting (I don't know if there is magic in 8, but you need to do it at least one full revolution, so why not several more).

Then you put the big torque to it. With luck, at that point nothing changes. But the initial act of snugging the nut has a tendency to change things a bit (sort of like setting valve clearance). Not fully torquing the nut at that point makes it easier to keep redoing it.

But let us hope that is for next time - or when you go help a friend do it. 0.01mm is under the accuracy with which you can repeat TDC, seems to me,

[LeakProof]

Thanks guys,

Bruce, I just put the spacer shims back exactly how I found them, four on the left and four on the right.
I was surprised also, at this number of shims. Thought I was screwing up, but checked my pic's and detailed notes.
With that being said, I would have to assume, that this configuration is original, and was done at the factory and this engine (107,000) has never been re-built.

Just for the record, This motor ran great and was only torn down because of a broken head stud, trans re-build and to fix annoying oil leaks.

"While your in there" got bigger and bigger, you know, head's, rod's, ring's, bearing's, cam, rocker arms, platue honing, etc.

One cam was pitted, and rocker arm bushings were worn. (my annoying ticking noise)

As far as sprocket's being worn, how worn, is the question?

If I had an endless budget, these would certainly all be new.

I suppose, I could pull the covers again to check the camshaft sprocket parallelism alignment, But why, if this is original to the engine, and no extensive machine work or upgrading was done.

I put this in the same category as, measuring piston to valve clearance.
Probably not necessary for my project.

Do you guys think, it would be a bad idea, not to check sprocket alignment?

Why, would I have an extra spacer shim on the left is the question?

Service Manual states. " Normally, when removing camshaft sprockets, 3 spacer shims will be found under the left sprocket. Key word 'Normally".

I would like to start installing the remaining rocker arms.

Thanks,

Leakproof.

[lindy 911]

If the sprockets are not aligned properly you'll start to get metal in your oil from chain and sprocket wear; this is not a good thing. How did you seal the gaskets on the chain boxes? If you put them on dry it will be no big deal to pull them and check the depth. If you used 574 (recommended) you will need new gaskets. Either way, I think it's time well spent now while the motors on the stand and not in the car. If it's not right and a problem develops the motor will be back on the stand in short order.

Pull the covers and make sure.

Lindy

[dtw]

I bought a 100k SC that was perfectly maintained and in pristine condition - that is, before the owner flinched at 100+ mph.

As I went over the records & engine on that car, I would have bet my eyeteeth that the motor had never been cracked. And indeed, as I tore the motor apart (it had inhaled a sheetmetal screw), everything looked virginal and untouched, just as Dieter left it in Zuffenhausen. That is, until I got to the shortblock and saw that the main bearing webs had been mooned by hand.

Moral of story: assume nothing.

[LeakProof]

OK, ok, ok, got it.

You talked me in to it, I think.

However, the Service Manual does state, "If new camshafts or sprockets are installed, camshaft sprocket parallelism must be checked.

I, of coarse did not do this.

Service Manual also states, "Normally, when removing camshaft sprockets, 3 spacer shims will be found under the left sprocket hub. Key word "Normally".

What does this mean? My engines is not normal?

Lindy, how did you know I found metel shavings in my oil. Maybe your on to somthing. This happened just once.

Covers are installed with Loctite #518. (also recommended)

Tensioner o-rings, probably can only take so much cover on and off.

Hollow bolt sealing rings, can only be used, I would think once.

I'm also getting tired of throwing away ni-lock's.

But, I will check the alignment and let you know what happens.

Thanks,

Leakproof.