timing belt alignment, again

[myhui]

I have everything apart. Would anyone near Orange County care to drop by to take a look? I'm in Lake Forest, 92630. Email me your phone number and I'll call you back to arrange it. Tonight would be best, but Sunday morning would be fine too.

The rear cam gears do not have engravings on them. I only see dabs of orange paint, and it's not precisely applied. It looks pretty close, but the paint is applied not just on a tooth, but also between tooth, making it rather ambiguous. The front bank's cam gears are spot on, and those are engraved, so at least I know the crank pulley has not skipped.

The crank is really easy to turn though. Just a 12" ratchet through a 20" extension can turn it easily.

Are all the cam gears supposed to be engraved? It's strange that the rear bank's gears are all smooth metal with nothing more than a dab of orange paint.

 

[Larry Bastanza]

The rear intake cam pulley has a small notch about 1/8" wide. The FACE of the rear exhaust cam pulley has a full line scribed in it. So it will look like this when aligned:


--- ]

The dotted line actually being solid and representing the Exhaust Cam Pulley.

The paint is probably hiding the small notch. Look carefully, it's there. The rear intake cam pulley is exactly like the front exhaust cam pulley.

HTH,
LarryB

 

[nis350]

Hi Larry,

You mentioned that if it is retarded a tooth on the rear exh. cam, it would have the v8 rumble at idle. I am just wondering if the rumble gets louder with increase engine rpm?

Are there any other signs? vibration? Lost of power? Not passing emission?

I am also wondering if one would retard the belt a notch to fit the belt, then advance it back to align the timing marks. Once the belt is tighten, wouldn't the timing remain aligned unless the belt slips a tooth between the rear intake and exhaust sprockets?

Another question is whether it is obvious that there is too much slack in between the rear sprockets even after tighten the whole belt assuming the above condition.

Thanks. :smile:

 

[myhui]

--- ]

I see it. Thanks so much.

I also thank a Prime member who came over tonight. He was tremendously knowledgeable and helpful. It also give me a perspective on how difficult this job will be.

I haven't removed the timing belt covers yet. That'll be the hardest part of this job, IMO. That'll be next.

One question: is it possible to have a low-mileage (27k), 8 years old belt on KGP's old car (99 Zanardi) that appears to be installed perfectly, and for all I know has not been disturbed since car left the factory, but due to age or engine abuse, is causing engine vibrations like the ones described earlier on this thread? It's felt as an imbalance type of vibration, like something out of round is spinning inside the engine. The engine idles smoothly, the injectors have been cleaned, fuel pressure is normal, IAB flaps check out, but from 1500 to 4500 rpm and beyond the vibration is still there when clutch is disengaged. The worst part is that clutch engagement is jerky, since power from each cylinder isn't uniformly distributed in time, so the clutch chatters. I checked ignition timing. It's advanced about 1cm beyond spec on the crank pulley when SCS shorting connector is plugged in with warm engine, but at 1100 rpm instead of 800 rpm since engine has cooled somewhat by then and ECU was probably running a rich mixture.

To phrase the question from another direction, is there a known problem with electronics or sensor malfunction that will lead to wrong ignition timing? Or must it always be a mechanical issue?