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Nein37 · Joined: 29 Dec 2009 Posts: 513 Location: New London, CT

I noticed while setting my idle timing that I had very little turn-in left to slow my idle speed and with the screw all the way in I'm just seeing the 0 in the timing window. Got me wondering if I could be off by a cam tooth.

So assuming the engine turns freely without any valve piston contact.

On a 931 with DITC, what would happen if after a timing belt change you mistakenly were off by one cam tooth?

Can the car still run really well?

Would your timing be slightly more advanced or retarded depending on which direction you were off?

John
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1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

Nein37 · Joined: 29 Dec 2009 Posts: 513 Location: New London, CT

OK, I guess I'll do the obvious and double check my marks. The only issue that I remember though, is that it seemed that with the cam mark set perfect the belt was in the middle of a tooth and I had to slightly turn the cam a little more clockwise to get the belt on. Could I be a tooth too advanced? And if it is, would my entire timing be slightly more advanced than it should be?
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1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

could your head have been shaved, which would explain being half a tooth off?
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Nein37 · Joined: 29 Dec 2009 Posts: 513 Location: New London, CT

No idea on whether the head has been shaved. Wasn't on my watch. If the cam mark looks too far forward I'll back it up a tooth, make sure it still turns free and give that a try.
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1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

Nein37 · Joined: 29 Dec 2009 Posts: 513 Location: New London, CT

Double checked timing... looks good. Might still have a vacuum leak somewhere. Its strange that my idle control is turned almost all the way in when properly timed.
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1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

Grenadiers · Posted: Sun Jan 13, 2013 8:40 am Post subject:

Check for hissing noises from your recirculating valve. I just installed a turbo in my CGT project, and forgot that advice while it was on my bench. Grrrr. Anyway, the frame side o-ring was totally missing. There was a metal on metal clank when thwipping the throttle.
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Throttle body shafts leaking?
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Nein37 · Joined: 29 Dec 2009 Posts: 513 Location: New London, CT

I'll check the recirc valve. I did the throttle body reseal about a year ago so I'm hoping that isn't the issue.
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1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.