Is cam timed incorrectly if crank mark is off by 1cm?

[wild man]

Got the car running today, but things get rattley around 2700-2800rpm. After several tries, I was unable to get the marks lined up perfectly. If the cam mark was right on, then the flywheel was past the mark by about a cm. If the flywheel mark was right on, then the cam was before the mark by about 1/8". Is my timing off?

[mikepellegrini]

What's 1 cm on the cam belt? A tooth? Or less? I think you're in the ballpark.

If you have vibration at around 3K but it's running fine otherwise, I'd say your balance shafts were off.

[rick13]

it's off, everything should line up perfectly.

[75ohm]

Redo the timing...

What car is this on and did you use a flywheel lock?

[zedsn]

My 83 NA was a tooth off and the car ran fine just didn't pass emissions. The balance belts was also off when I bought the car and the car had vibrations at 4000 RPM +.

[MrTibbs]

I've just redone my belts for the first time. I was pretty nervous about it and had a bit of a similar issue. When I got the cam mark lined up it looked a bit like the mark on the flywheel was off - I could see it but it didn't look lined up against the line on the bellhousing.

I turned the engine so the cam wheel was off the mark by one tooth, and the mark on the flywheel had disappeared.

So (although I've not had my car long, so am not an expert) I reckon if you've got the belt on and the cam wheel is lined up with the mark and the flywheel mark is visible it's probably right.

If the belts stretch a bit (which they do, otherwise there wouldn't be a need to re-tension) it's not surprising the lines wouldn't line up absolutely exactly.

Hope this helps

Mike

[mattdavis11]

I have found myself using the TDC line on the flywheel sometimes, most of the time I mark things with nail polish. How far you (can) lean over the motor to see the mark makes a difference. Eye dominance could be another factor. I align with my right eye, never with both.

What looks good to you, might not look right to me. Flywheel mark is past TDC the way I see it.

[mikepellegrini]

I just looked to see exactly how big a CM is - 10 mm - and that's pretty big (I'm an American and metric-stupid); that would be an unacceptable margin of error if you have the belt that far off. That'd be 2-3 teeth or maybe even more.

1/8" however, is about one tooth and that's okay.

I don't understand how you could have everything lined up properly and be more than a tooth off.

You line up the flywheel mark, then line up the cam, I can see how maybe TDC on both with leave the belt falling in the middle of a tooth on the camshaft, but that oughta be the extent of it. You shouldn't have to move the sprocket more than a half-tooth or so to get the belt to slide onto the teeth. If that's what you did, then that's great.

It's how it runs that's the final test. In your case, it sounded like it was running good - so I wouldn't screw with success.

Vibration at 3K RPM is a classic balance shaft timing problem symptom.

[HondaDustR]

If you mean 1 cm of movement of the mark on the flywheel, then that's not really that much, but it would be better to re-time it leaving the crank on TDC to make sure it's not 1 tooth or more off on the cam (1.5 teeth on the cam is roughly 15 degrees on the crank, or so they say, just FYI). The timing marks will seldom ever both line up perfectly. Set the crank to TDC as accurately as you can using the flywheel mark and then time the cam to the nearest tooth that will get the timing marks as close to lining up as possible. Between manufacturing variances and the fact that new belts are a bit tight, the marks will never line up perfectly. 1/2 tooth on the cam sprocket either way is normal. Re-check the balance belt timing and make sure you put the balance shaft sprockets on right. It gets confusing with the later motors that weren't marked the same as the early castings. Would be worth double checking as it's easy to get mixed up. Balance Shaft Sprocket Installation and Alignment Check

The rattley noise could be belts slapping around from being too loose, depending on the interpretation of "rattley".

[Arizona_928]

I use the OT mark on the flywheel. when that is lined up dead on, the cam should be perfectly set on the dash marks. Pretty fool proof method..

[wild man]

I also get some vibration noise from down by the shifter at various rpms - kinda goes in and out. The strange thing is, when I first timed it, when the crank timing pulley was on backwards, everything seemed right on the marks. But that time I did use the inside cam mark. This time I used the one where you look through the hole through the outer cover. And this time I did not have the front of the car up to where I could see the crank/bellhousing notches visually. I used my finger to feel if they were lined up or not, and it ended up being about a finger off (1cm-1/2", roughly). I need to check if the exhaust is vibrating against the underside of the car. But I think I need to re-check the timing too.

If it is allowable to be 1/2 tooth off, It could be 1/2 tooth off in the WRONG direction maybe.

[rick13]

you are going to break something...like your exhaust manifolds. check your balance shafts. ask me how i know ...everything should line up perfectly !

[Arizona_928]

Your timing should be lined up perfectly. If it is 1/2 a tooth off, you didn't set the timing right.
The balance shafts could be 1/2 tooth off on one gear, However on the other gear the timing marks should be perfectly dead on.

[wild man]

Originally Posted by rick13

you are going to break something...like your exhaust manifolds. check your balance shafts. ask me how i know ...everything should line up perfectly !

Sounds like what must have happened to the PO of my 951. The #2 runner has a weld bead all of the way around it, about 6" from the head. I have a receipt stating that the work was done. Another receipt that I have says that the balance belt broke & was replaced, along with the timing belt @90K miles. There is nothing showing that the belts were ever replaced prior to that, so maybe it was a GOOD thing.

It really isn't vibrating that badly. The (ABS) steering wheel vibrates up and down maybe 1/8" when idling, with hands off. I'm still going to redo the timing. But this time with the car back up in the air, so I can get a good eyeball on the flywheel mark. And I will probably pull the cam pulley cover off also, so I can use the mark that is behind it, rather than the one seen through the hole in the outer cover.

[mxfrank]

Has this engine ever been worked on? If some rebuilder has surfaced the head or block, it's possible to screw up the timing by reducing deck height. For other cars I've worked on, there were thicker headgaskets available that could restore deck height. Not sure about the 944. But I think it's likely that you're just off by a notch.

You really have to lock the flywheel so that you don't have to worry about losing crank position while you do this. Too many moving parts will ruin your day. The cam rotates at exactly half the speed of the crank, so 10mm at the flywheel is probably about one notch on the cam gear.

When I did my timing belt, I found that the camshaft shifted almost a full tooth counter clockwise when I released the tensioner (this on an '88 with a spring tensioner). This made sense, as there was more tension on the tensioner side than the free side, due to the crank being locked. What I did was to secure the tensioner off the belt. Then I used a 34 mm socket to move the cam gear a bit to the the left of the mark (have to be careful not to go too far, and bend a valve). Then I installed the belt, and used the 34mm socket to tension the free side of the belt. Without releasing tension on the cam gear, I then released the tensioner, and viola, the gear was dead on the mark, with perfect tension on both sides. Checked everything 1000 miles later, and it was still right on.

[wild man]

I dunno - it's not like I can feel any vibration. But there is a lot of stuff lying around inside of the car right now that can rattle - and much of it does. I suppose that using the sight holes, I can check if the timing is on, without having to take anything apart. The car will be getting jacked up tomorrow to fix an exhaust leak, so I'll check the timing then.

BTW - the jumping of a tooth when releasing the tensioner is a common occurrence.

[porsche4life]

Set the timing, rotate two whole rotations by hand, reset timing.... Oh and be sure to mind your Os and Us...

[wild man]

Originally Posted by porsche4life

Oh and be sure to mind your Os and Us...

All right, it's got a nice "ring" to it, but late cars (88+) have no Us, only Os. Call them double-ought maybe? I guess that was dumb. Anyways, each one has an O (actually a 0), and a blankie slot. IIRC, the blankies are where the keys go, and the 0s are where the outer guide locating tabs stick into.

Can someone verify that this is correct? Could I have it backwards? Here I am, relying on my sometimes faulty (and getting worse with age) memory again.

[wild man]

Since I am now ready to go out and do this, I decided to check with clarkie. And guess what? Not correct OR backwards! It's a split decision. First off, the "late" ones are 85+, and they are set up the same as the earlies. The only difference is that the U's aren't stamped into the BS timing pulleys. The lower one is correct. The blankie (formerly U) is the keyed one. And the upper one is incorrect. Clarkie says that the 0 (or IS it an O?) is supposed to be the keyed one, for the upper shaft. Time to go out and fix it...

EDIT: I could swear that the way I had it is the way it was previously. So maybe it's been wrong the whole time. And I now recall a thread regarding this a while back. So It now appears that what I stated in that thread is INCORRECT! I'm surprised that no one "checked" me on that, but I suppose it happens sometimes.

Oh, and thanks PFL, for mentioning it!

[Slam]

Very simple. BOTH keyways on bal shafts face up, slip the sprockets on aligned with the timing marks.