Cam timing in the car? Possible?
 

Can you adjust cam timing in the car? Do you have enough room with the muffler and tin removed to get the wrenches on and torque the bolt?

After a less than statisfying first start, I has diagnosed the RHS cam is off.

Not my best day.

911sc, 3.0l.

I've done it before, truly not worth the extra effort. Engine still needs to be lowered.
Bruce

Diagnosis......
 

VFR750,

How did you diagnose that the right side cam was off in timing? You could do a partial engine drop to gain access to the cam/s and it would be very awkward doing this job that requires precision measurements. What is preventing you from doing a full engine drop and do the cam timing with the engine on a bench or engine stand? What you are thinking is doable and could be done easily by people with skill and experience.

If you made a mistake doing the cam timing with the engine sitting on an engine stand do you think you could do better with the engine installed? I've performed more than a dozen cam timing settings and would not even consider doing one with the engine in situ. This is a decision that you have to choose.

Tony

Engine almost out....

I timed the LHS perfectly. And it is still in spec.

The RHS is off again. I verified in the car. There is enough room to do it.

It is supposed to be set at 2.4mm. And it came out at <1mm. About 30 degrees retarded. Very odd. I am way off on the RHS.

But this is the second time I've found the RHS out and the LHS in spec.

Something is going on. Is it possible to jump timing if the hydraulic tensioner poops out? Would it jump to a retarded position? That wouldn't explains first error. But I was really paying attention the second time.

I'm using the stomski mechanical adjusted to set the timing. So I should have no issue with tensioning the chain.

Carrera tensioners installed.

Thought process isn't right. If you jumped a cog you would be off way more than 1,4.
Bruce

Its possible . . . just awkward. I actually have a fixture from over fifteen years ago that takes the place of the engine mount to allow open access to chain housings and crank pulley. (Been at this for a while)

Based on the angular difference between the left and right is that enough to be off a tooth?

What I mean is, the angle of rotation on the crankshaft to reach 2.4mm lift difference between the LHS (good) and the RHS (retarded) is around 30 -40 degrees.

That feels like a sprocket tooth difference.

Added info.

I heard some rattling for a brief moment. Since I have a loose baffle in the muffler I thought that was it.

Now I wonder, could that be a bad tensioner, sagging when shut off, and then repressurizing on start up?

It takes about 30-40 degrees rotation to go from just touching the ramp to get to 2.4mm on the LHS.

I will try to check and get better numbers to verify if the difference can be explained by a tooth jump.

Thanks for the push back. What it means to me is you are pushing me to think about it more. Which is ok. It challenges me to be very specific about what the difference is. Left to right. Is it exactly one tooth off?

Just looked at a picture of the cam gear. Looks to be 36-40 teeth. Jumping One tooth would be 16-20 degrees in crankshaft position relative to the timing.

So I've confirmed, jumping 1-2 teeth could explain the problem.

Carrera pressure fed tensioner

Well, I'd look at something else. One simply does not hear of chains jumping teeth. If a tensioner lets go, you get a horrible rattle, exacerbated some by engine speed. People drive home knowing their tensioner is shot. Of course, they pussy foot it.

Bruce says one tooth is more than the 1.4mm change you show. He's got a lot of experience. And I don't think the chain can jump a tooth on the sprocket on the cam, which is the big one. If it jumps, it would be on the smaller gear on the intermediate shaft, and that is going to have a lot more influence on timing. Remember, there is a gear on the crank which turns the IS shaft at a lower rate. Then the chain gearing turns it lower still, though the combined effect is 2 to one (the reason for this sort of offset gearing is to be sure the gears and chains wear evenly).

And it only takes a tiny cam change to move the valve 1.4mm or less where you measure it.

Tensioners don't sag. The tension is created by the spring inside. The oil just acts like a shock absorber, dampening the harmonics otherwise present. So you have the same tension at all times, it just doesn't work well if the oil pressure part fails. And it isn't the pressure of the oil coming in which matters - the purpose of the feeding is to be sure that the oil chamber is full at all times so it can do its shock absorbing task. Fact is, solid tensioners work fine on race motors if set carefully. It is just that they have to be checked often, and aren't right for the extremes of day to day driving.

Which type of cam do you have? The earlier big nut kind? Or the later, harder to adjust, bolt kind?

Why don't you take some pictures of your cam timing setup and post them?

First, I said <1, and that 2.4mm came 30-40 degrees ATDC. That is of the same magnitude as a couple of cam sprocket teeth or 1 intermediate shaft tooth.

What you said makes sense that the smaller sprocket could have jumped if a loose chain overshot the sprocket.

Also, I did hear a horrible rattle, but I assumes that was the loose baffle in the muffler. But I had never heard it before and it went away after a short while. I did not time how long. In retrospect, it was abnormal and I should have stopped right there.

I cam show you how I timed the cam, but it will look like the LHS. Dial gage, extension shaft, Z-block. Resting on the outer flat of the retainers. RHS just like LHS. LHS has not changed. Later style with bolt and pin.

Cams are a custom DRC dc20/19 with 110 lobe centers, combined with DRC springs. So the forces on tbe chain are a lot higher than stock.

Other things to consider, before I tore down the engine I had a ticking sound, later confirmed to be a loose cam gear on the crankshaft. Also the RHS idler arm bushing were worn way over spec. Both were fixed/replaced. I kept RHS tensioner on the RHS always.

Part of the reason I pulled the engine last year was it was running poorly and oddly loud. I also found a blown head gasket on #2. Had previously ran at Thompson Moter speedway road course.

The sounds I heard on the test drive sounded similar to before the rebuild.

Related?

Don't know.

But all data that needs to be considered.

At least the oil came out pretty clean and nothing on the magnetic drain plugs.

The left hand side chain is more difficult to make sure for proper engagement on the IMS gear but... That doesn't mean it can't happen. It's possible your right side chain was not over both teeth. Happens a lot when setting up timing chains on aflas. Did you notice if the chain was "tighter" on the RHS? It's possible that it wasn't fully engaged and once you start it, it found the happy place and shifted the timing by a tooth. Low probability but that why I roll the motor over a dozen or so times before I start making final adjustments. Either way, you'll get it sorted!

As part of the timing process, you rotate the crankshaft several times and verify the timing repeats. Which I did, and it did.

Any chain anomaly during the first setting would disappear when you rotate the crank through several cycles past TDC.

But it is something to be conscious of

If you screwed up the cam timing too much and ran it, you'll be into bent valves contacting the Pistons especially on the exhaust side.
I suggest you pull the engine, put it on the table and find out what the problems are. Everything should turn smoothly and be in sync.
Chains don't just jump, cams don't get off spec by them selves, and strange noises aren't part of the rebuild. You're trying to work upside down and resolve the problems, pull the engine and save your self time and agrivation
Bruce

Engines out and the teardown has started.

Yes I ran it, and it was not smooth. So, yes I have already screwed up. Inexperience does that occasionally.

I have JE pistons, so hopefully the deeper pockets help in avoiding valve contact for the magnitude of the timing difference.

The 110 lobe center is much less aggressive than the 98 used on some cams. And the duration is similar to the 964 cam. My fingers are crossed that this was a mild enough cam to avoid piston contact.

Here is my setup: I'm setting up to check timing now.
http://forums.pelicanparts.com/uploa...1432081997.jpg

10mm range Dial indicator on the large flat on the retainer. Set at 9.0 mm deflected, looking for 6.6mm for 2.4mm lift. Valve clearance set to 0.1mm (0.004")

This is what it looked like when I did it:
http://forums.pelicanparts.com/uploa...1432082547.jpg

What is the cam spec for setting valve movement on 360 degree rotation of crank. I don't understand the concern of 6,6.
If 2.4 is your spec, valve lash is .1 mm, that's the only numbers you should be concerned with. The 9.0 and the 6.6 is useless information.
Bruce

You start at TDC (valves closed) Z1

Set the dial gage at some value. Whatever you choose, you have to compress (deflect) the dial gage such that you can measure the motion of the valve. In my case I precompressed the dial gage 9mm.

Rotate the crankshaft 360 degrees back to TDC.

At that point there should be 2.4mm of lift.

9.0mm - 2.4 = 6.6mm on the dial gage.

That is how it is done.

My problem is my RHS is now requiring 30-40 degrees past TDC to deflect the valve 2.4mm. Which is bad.

The 9mm I refer to is just my starting point. You can do any value you want, provided the dial gage has enough range to deflect 2.4mm ( for my particular cam)

Deep breaths and go back to basics. Dots up at TDC 1 and start over. You shouldnt have to take off LHS cam nut if it's ok but reset RHS to dot up. Make sure you're at TDC 1 though or you'll be like that other guy on the forum that timed his cam backwards. Sounds like you rally understand your gauge and are just using a relative measurement. If it were digital you could zero it. But you way works perfect too. Take your time. You've already done the hard part of pulling the engine back out. If your cam was that far behind the piston is on its was down long before the valves opened. But you can double check with a leak down gauge to be sure you didn't bend anything. Whatever you do, don't give up. You're so close to being done!

You have to do the same thing to the right side. With crank at 360 degrees rotation from #1 set the right side up and rotate 360. At this point you pull the cam pin and move the cam to the 2.4 and pin.
You have to start with both key ways up and both cams pinned. You have 720 degrees of rotation to set up the 2 cams relationship to the crank.
Bruce

Thanks for the encouragement. It has been a numbing experience.

I think most of us set our dial indicators to zero when the rocker is on the cam's base circle with 0.1mm lash. Does away with any math at all. After rotating the engine, you watch for the valve opening, and when it gets to the lift specified, see where you are relative to Z1.

I've taken to using electronic dial indicators. Easy to zero, and I can use metric. Not that expensive any more, and you don't have to keep track of rotations of the needle. I've now got two sets for doing this, which is a great help in avoiding right side/left side mistakes as you can watch both while setting either so you can see that one side is on its base circle while the other is opening up toward the overlap spec.

Metric analog indicators for some reason are way more expensive than inch ones (which are cheap), so mainly I have used inches in the past.

Walt,

My metric dial gage goes from 0 extended to 10 fully compressed. So I have to compress it to some large value, like 9, then rotate the face to get the pointer at exactly 9.00mm. Then target the delta to reach 2.4mm at Z1

Being able to read directly would be nice, but not an option on my dial gage.

I do as you mentioned. Set "9.00" when off the lobe (position at TDC compression) then rotated 360 degrees back to Z1 and read the gage. 6.60mm in this particular case.

I write down all the numbers and steps followed. And I repeat the measurement after final setting.

I mark the sprocket and the drive gear where the pin is. And can easily rotate the two relative to each other to change the timing. I remark the pin location, retorque the bolt, and check timing three times. Keep doing that until I reach the desired value.

That is the fustrating part. I got 2.4 on both sides when I was done. LHS still reads
2.4mm and RHS is barely 0.2mm. It takes another 30+ degrees past Z1 to reach 2.4mm

Today I'll be checking the timing and correcting.

As of last night, leak down showed all cylinders about equal. And all were leaking past the rings (air leak audible through breather port). So that's a bit of good news.

OK!!!

I am to blame.

I just confirmed that letting the RHS idler drop, when changing out the stomski tool for the real tensioner will exactly cause my problem.

The chain gets pushed back towards the intermediate shaft sprocket. When I lifted the idler to install the hydraulic tensioner, I had to rotate the crank to lift the idler.

Plus I measure the angle of 2.4mm lift currently and it was ~25 off. Now it just took me another 25 crank rotation to lift the idler into position. One tooth.

I now have the smoking gun.

And it is me.

Thanks all for your help.

Oh, and to add insult to injury: "so that's what the red numbers on the dial gage are for!" For going backwards!

Walt, thanks for being patient. I even took pictures confirming my error.

At least I can move forward.

Funny thing. Pulled pin, rotated crank and stopped 25 BTDC and pinned cam.

Rotated to Z1 and got 2.15mm on first try. Index pin one pin hole over got me 2.45mm. Done.

The last statement is the wrong answer.
You don't pull the pin, rotate the crank, then repin the cam at 25 btdc.
You keep the pin in cam drive until you get to z1 then pull the pin and adjust the cam to your setting then repin. Then rotate 720 degrees and check setting
Bruce

Actually you can. The cam doesn't rotate with the pin out. So you can reposition the crank relative to the cam, and then pin it.

With the bolted type it is very hard to turn the cam. Is easier to move the crank.

At least it is for me. That's how I did it to prove I was off 25 degrees. Only took one tiny adjustment to nail the required timing.

I like the old, big nut, style cams when it comes to ease of setting cam timing. You can't rely on the pin settings (at least not without some fancy footwork) to dial it in precisely. You can get a fair range of settings within any one pin setting, locking in the setting you want with the big nut. And really little trial and error - rotate cam to setting you want, and tighten big nut, but not to full torque. Check to see how much locking changed setting. If not enough to bother with, go to final torque on the big nut.

I could approximate this by using a small screw driver against the inner sprocket teeth to move the cam a little. When I tried the bolt with locknut method, the cam always moved some when unlocking the nut, but perhaps with practice I could have overcome that.

I can see how you could just move the crank. Easy if you need to shift the pin (and have figured out which way to go for the change you need). But hit or miss when fine tuning, since you don't have the dial indicator to tell you where you are while moving things.

I agree with the bolt style and pin there is some variability. I found I could use a small screw driver to rotate the drive gear and it is worth ~0.3mm near the target

Obviously I lost some credibility with my idler gear goof. But overall the Motion of the crank to cam is straightforward. And with some thought I was able to predict what was needed to get close.