Black51

Last week my cam bolt backed out so far it nearly came off. I put it back on with locktite and went to fire up the car. Since putting the bolt back in place, the car runs running at ~1-2 in Hg of vacuum at idle, and obviously has no power. The belt is also ripped up pretty badly. I'll have to swap in another one when I get the chance. The car was running perfectly before this.

One strange thing is the car still boosts, but takes a very long time to get into boost.

Is low vacuum like this an indicator the timing is off?

EDIT: I did already inspect the vacuum system.

Paulyy

you should get a timing gun/strobe and check if the timing is actually out.

Rogue_Ant

Paulyy is correct - best to get a timing light out, or just line the crank up at TDC and check it out.

To answer your question, yes, low vacuum can be a sign of an incorrectly timed engine.

Black51

Thanks. I'll have to line the marks up and check timing hopefully this weekend.

ausgeflippt951

If your belt is ripped up badly I would recommend you don't drive the car until you can replace the belt. I've seen belts in seemingly A+ condition break for no good reason, so if it's already ripped up then you're just asking for trouble..

ramius665

You did confirm that the crank and cam were both lined up properly?

Ronin-951

JohnKoaWood

Supprised noone has mentioned yet..

The CAM bolt is a one time use stretch bolt... if it came loose, it needs to be replaced, not just tightened down as having one shear durring use WILL wreck your head!

You should order a replacement along with a new timing belt, I wouldn't bother with doing anything else till the belt and bolt are replaced!

Black51

Ahh, never knew that! Thanks John. Probably why it backed out after putting it back in.

After completing a HG replacement a few weeks ago, the timing was spot on. But I think somewhere between the bolt backing out, and me putting it back on, it the cam sprocket must have moved enough to allow the belt to slip.

With the belt in the shape it's in, and the way the car is running, it hasn't gone anywhere for a couple weeks. I may be dumb, but at least I'm not stupid.

Tom M'Guinn

Not sure why people are suggesting an ignition timing light to check the valve timing? I'd line up the cam gear and flywheel TDC marks to see if the cam is timed correctly still. If the cam gear came loose, you may have sheared the woodruff key in the cam, which will lead to unpredictable and inconsistent valve timing even after bolting it up in the right position.

Black51

That's what i have planned Tom. I remember seeing the woodruff key when I popped the rotor off; if that's the one you're talking about. It appeared to be fine, but it'll be too easy not to have a closer look at it again when it's apart.

Rogue_Ant

With a dial-back timing light, you can check cam & balance shaft timing. Though I agree that the best approach is to simply set the engine at TDC, and check the cam.

Black51

I have to change the belt anyways, so ya, that's how I'm gonna do it.

To be clear, would simply having the timing off cause 'that' low of vacuum?

Rogue_Ant

Possibly, if the cam was way retarded. ()

hp18racer

I had the cam bolt come loose on my car once. It damaged the key and the cam so that there was a half tooth of play. In this condition compression test showed half the normal value.