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Armed Bastard
 
djb25's Avatar
 
Join Date: May 2005
Location: North Central PA
Posts: 351
Okay... anyone want to give me a rundown on cam timing?

I pulled the upper valve covers and both cams seem synced. However... according to my little tech specs book, my intake valve should open 6 degrees ATDC and should close 50 degrees ABDC.

From what I can tell, my intake is opening about maybe 2 or 3 degrees BTDC and closes around 50 degrees ABDC (determined by counting teeth on my 36-1 wheel).

Now, I’n guessing that “iintake opens” is supposed to be when the valve begins to open. Is that correct?

If so, I’m now wondering if the timing marks on my pulley could be off... if that were the case, could that difference be the cause of my problem? I’m thinking that they could be off by roughly 8 degrees... which happens to be what my idle advance is set at.

I think that would mean that I have the ignition advanced 16 degrees at idle, right?

I’m just looking for some confirmation of my numbers, so if anyone could help out, I’d appreciate it.
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Damion
'77 911S Turbo, EFI 2.7l, Carrera intake, Megasquirt 3 with MS3x, Fuel & Ignition
Old 08-23-2017, 04:44 PM
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Armed Bastard
 
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Join Date: May 2005
Location: North Central PA
Posts: 351
Well... I think I found the problem.

Iím apparently having an ignition issue. From the looks of it, Iím not getting spark to cylinders 2 and 3.

Here are the plugs from the left side of the engine...



Brand new plugs, obviously...
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Damion
'77 911S Turbo, EFI 2.7l, Carrera intake, Megasquirt 3 with MS3x, Fuel & Ignition
Old 08-23-2017, 05:00 PM
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Registered User
 
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Quote:
Originally Posted by djb25 View Post
Well... I think I found the problem.

I’m apparently having an ignition issue. From the looks of it, I’m not getting spark to cylinders 2 and 3.

Here are the plugs from the left side of the engine...



Brand new plugs, obviously...
That would do it. Essentially those two dead holes would be pumping unburnt fuel into the exhaust. A digital pyrometer would also be useful to go from each exhaust runner per cylinder and look at the temps. It will be quite evident if you have a cylinder or two that are not contributing.
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-Jayson
1976 911S Signature Edition
3.2SSt (JE 98mm 9.5:1 pistons, 964 Cams, ARP Rod Bolts, Big Port SC Heads, 3.2 Carrera Manifold, ID725's, B&B Headers, Tial 44mm, TS RacePort, BW S360, AEM Infinity 506, E85)
Old 08-23-2017, 05:39 PM
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Turbofrog
 
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Join Date: Aug 2009
Location: Europe
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You can spot the DTC with a long thin rod on #1 plug hole. Just watch when its in the middle of up/down movement turning the pulley carefully. Not 100%accurate but should show wrong marks on pulley.

Those plugs look like they newer had spark and fuel on them.
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79 930: HX40S#16, MS3pro+ID1000+044+E85, Ignition: 123/TUNE/MSD6A, True split BB, 2*turbosmart38,
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Old 08-23-2017, 08:50 PM
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You can check the cam timing with the engine in place - except I don't know how many non-stock bits you have on top. The RHS is usually not an issue but you have to clear some space on the LHS. Enough to mount a dial gauge on preferably #1 and 4 Inlet. But not essential, #2 will do - you just use another crank TDC mark. Make sure your valve clearance on that one is correct first. Otherwise you can do an eyeball check - depends how good you are at judging 1-2mm depression on the valve. You wouldn't set them up like that, but you can check if something has gone wrong, that way. BTDT. Basically you will want to check each bank has same Inlet valve depression at TDC for that valve. Any valve on each bank basically will do. But if you have dropped a tooth one bank will be quite different.
No idea if a turbo makes a difference, but suspect not. The valve timing for the 930 is not greatly different to an SC, depending what cam.
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 08-23-2017, 11:30 PM
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Sorry - hadn't caught up with page 2 -
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 08-23-2017, 11:32 PM
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