Degreeing cams

A long time Fcar mechanic showed me something he learned at the factory. Once the timing is set so close that moving the locating pin one hole is too much you can loosen the can sprocket locking bolt and then slightly rotate the crank in the direction you need to correct just enough to pull tension on the sprocket. Tighten the sprocket bolt before releasing the tension. This will give you a few more thousands of correction.

 

Aaaand I was wrong. I got it just about exactly right, well within spec. Just took more time than I wanted it to!

 

Yes, that would be akin to loosening the cam bolt and tapping the cam with the rubber mallet while the dowel is still in; there is a little wiggle in the dowel. That's how I got it!

 

One more trick to add to the bag.

Thanks Joe and Pete.

 

It is time for a major, prior to offering up the car and I just printed out this thread to try to be able to get it right.
Having never dialed in the cams, I am looking forward to the process and getting it timed right, (euro spec) for the next caretaker.

This forum was the reason I felt comfortable enough to buy a 308, and I am still leaning on it and loving it.

I must scale it back a bit, moving into retirement, wish I had been a bit more clear sighted about the future costs, but ah hell, it is what it is.

Looking forward to studying the collective wisdom re: timing.

Thanks Guys,
chris

 

Well for that answer you need to calculate how much .015 is in degrees. they give you +/- 1 degree and it is achievable. Sometimes no hole will line up within that. I just take the sprocket off and relocate it and try again.

 

That works to some level most of the time. Some cars the hole/pin is a loose fit and you can get an entire degree, sometimes nothing but it is always worth a try. I cinch the bolt while turning in the direction desired.

Some of the motors have holes drilled around the entire circumference of the cam and the sprocket. Those are pretty easy. Some of the 8's and the flat 12s had three holes and they can be an exercise in removing and relocating sprockets.

 

Brian,
Indeed, I was able to get it torqued exactly in spec; I detailed that in my other thread. Thanks for the help!
PK

 

Yeah. Until it's not in spec.
The whole point of the exercise is that the cam needs to be in spec AFTER the cam bolt is torqued. It can be in spec before you torque the bolt, but the process of torquing the bolt will often lock the sprocket to the cam out of spec. After you have torqued the bolt and you rotate the engine over again and return for a second measurement, the cam is out of spec again. That's because the torquing process allowed the cam to move slightly relative to the sprocket.

The way I got around this with my car was to set the cam further out of spec than it should be prior to torquing, which allowed for the slight shift in the relationship of the cam/sprocket during torquing. Now that the bolt is torqued, I can repeatedly turn the engine over and measure the lift at TDC to be exactly what spec says it should be.

 

First of all, great post and really informative. Finding TDC was easy with a glassfibre rod on the piston and a guage.
But I have a question regarding finding the start of the opening of the intake valve.
When turning ClockWise as mentioned, and as suggested (rotation arrow)by the degree wheel, the first action to start on the degree wheel is the exhaust valve moving, not the intake valve!
So should I turn Counter Clock wise for intake valve action? Or turn an almost whole cycle of say 300 degrees to see the intake valve open? That would mean that the TDC is not the TDC of the cycle that pushes out the burnt gasses, so the wrong one.
Turning CCW should see the first action as "end of closing" of the intake valve, so that would not be 28 degrees I would think.
I am sure I am missing something here, but what?



and on TDC, the marks are off by more than I expected. Is this normal? As much as 10-15 degrees off on the degree wheel! I have checked TDC several times, in more positions of the rod on the piston, as straight as possible (pic shows crooked setup, but still gave same reading)
I have not measured the degrees of opening and closing of the intake as I first wanted to know how to measure, Cw or CCW for the intake.

Please enlighten me some more! Thanks.
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I haven't read this whole thread so I'm not at all certain about this, but it sounds like you might be at TDC on the compression stroke when you're wanting to be at TDC on the exhaust stroke? See if rotating the crank 360 degrees puts you where you want to be with the cams. Remember that the cams turn at half crank speed, so rotating the crank 360 degrees will move the cams 180 degrees.

FWIW, I'd look for a more accurate way of determining TDC before actually timing the cams.

Good luck!

 

Thanks!
As the marks on the cams are only about 4-5 mm off, I assume I am on the right cycle, as another 360 turn of the degree wheel (and crankshaft) does not show marks on the cams.
Still puzzled...

 

Two 360's on the crank = one 360 on the cams.


To get the extra 0.5 - 1.0* +/- or anywhere under on the cam, I use my wife's nail file on the pin. Very Slight sanding makes a very Big difference.

But don't tell her that.

 

Sorry, but I do not understand it?
Thing is that I am sure I am on the right cycle (as the cam marks almost line up, 4 to 5 mm apart, on any other cycle they would not even be visible), but when turning CW I first encounter an exhaust valve movement on the degree wheel. When I should encounter an intake valve action...
Could it be that the degree wheel is a mirror image from what is needed with this engine?
It is normally used for US V8's with a central camshaft.

 

If you turn your crank 360 degrees once your camshafts have only spun 180 degrees that's why you don't have cam marks after one spin of the crankshaft.

 

I do have cam marks, only they are 5mm off! And that is a lot I think, could well be 20 degrees on the crank/degreewheel.

I have to admit that the picture of the marks is not that clear, but if you look carefully at the pic you can just see a faint mark about 5 mm off. The mark (on the cam) is filled with oil, so a bit shallow and not visible well.
But it is there, and 5mm off. To me that sounds like way, way too much off.
Anybody ever seen a mark that much off, after having checked TDC like 10 times?

Maybe I better check on cilinders 5-8 first, to see how they are tdc and marks wise.
Maybe my 1-4 belt has jumped a tooth before (not on the current set of belts and tensioners, they look good and within spec.

As far as I know there are no factory tdc marks on the flywheel on a 355, right?
The pm 1- 4 and pm 5-8 are from other models?

 

Something is very wrong with your procedure. The marks cannot be that far off.


The process is very simple. Find and mark TDC. Turn the motor to TDC overlap and check your degree wheel adjustment. Turn it back until the intake valve is closed +20 degrees or so. Set dial indicator on intake cam follower exactly parallel to valve stem with indicator set to 0. Turn motor in direction of travel until the valve is open the amount shown in the service manual. At this point the motor should be at TDC. If not readjust sprocket as required. Once you think you have it test 5 or more times for an average because the cam follower often turns slightly upsetting the measurement.

On the exhaust side start at TDC and measure how much the valve closes.


It is really that simple. If it does not come to you seek help from someone who has done a bunch of 355's.

 

I agree, something is not right at all.
This is my procedure for finding TDC:

- In the plug hole of cilinder 1 I have inserted a glasfibre rod, that rests on the top of the piston.
- the dial gauge is connected to that rod. The dial gauge is stabile, see pics.
- I have turned the crank clock wise till the marks on the cam caps and the cams line up.
- then I have turned the crank CCW some 30 degrees, and have watched the dial hand move as the rod is being pushed upwards, translating into hand movement on the dial.
- the hand stops moving when the piston is on its highest point. Overshoot, and turn CW. When the hand stops moving again (highest point piston), then I have set the pointer on the degree wheel to the TDC mark.
- next step is turning the crank CCW and CW to find the real TDC without the slack in the connections. When done, that was my real TDC. Slack was only 1 degree by the way, so never of influence to the present problem. Crank left at TDC.
- then I looked at the marks on the cams , to notice they were 5 mm off, and not 1 mm or so which I had expected...
- engine was running before service. Would an engine with a skipped belt tooth on one bank be running? Because that is what I think has happened in the past. The present set of belts and tensioners is ok, tension at 2.5 mm, belt not dry, service was just because last date was not known to me. I just wanted to see if the cams needed degreeing, but now I am unsure what to do next.
- would correcting 5 mm on the cam (25 crank degrees??) be lethal if I would have made a mistake somewhere?
In other words, should I correct it or not?

 

I cannot watch over your shoulder so I cannot comment on your process.

 

Thanks for the info, that is indeed also a good way to find TDC. I will look in the WSM to find the amount it has to be open, I have seen the table somewhere over here as well I remember.
I will be working on it tonight, will post my findings.

 

If you were not doing that, what were you doing?