Ignition timing with DC15 cams

Aurel · Aurel's Garage

I need a bit of advice here,

So I rebuilt my 3.0 motor with DC15 cams, and I got it started. I set the ignition timing to 5 deg past TDC, but it does not run right like that. The motor dies if I open the throttle wide. I was wondering if DC15 cams require a different ignition timing?? Note that this could be another problem, like a spark plug not firing, or an injector not spraying well, but I`d like to know if 5 deg past TDC work for these cams first.

Aurel

MatthewBrum · 05-23-2008, 12:13 PM

Is the timing really set after TDC? Usually timing is set before TDC.

Aurel · Aurel's Garage

On my SC, the 5deg mark on the pulley is after the the Z1 mark, clockwise. So that is past TDC, I think. Then, at higher rpm, the vacuum advance mechanism brings it about 30 degs before TDC.
So, I was wondering, with a different cam profile, if I should set my initial advance at a different value. The DC15 have 1.9-2.0 mm overlap at TDC, while the SC have 0.9-1.1 mm. Does it make a difference for ignition timing is my question.

Aurel

JohnJL · 05-23-2008, 03:21 PM

Watch your pulley turn over again, it runs clockwise and those marks are BTDC. You should curve your distributor for each specific engine configuration for max results but depending on your application might be "good enough."

Search under my name and "ignition map" and you'll find a map for a very similar engine to yours. I've posted a map for a 3.0 with DC20 cams and EFI. I spent a lot of dyno time working on that ignition map, you're welcome to use that as a starting point.

Aurel · Aurel's Garage

Quote:

Originally Posted by JohnJL

Watch your pulley turn over again, it runs clockwise and those marks are BTDC. You should curve your distributor for each specific engine configuration for max results but depending on your application might be "good enough."

Search under my name and "ignition map" and you'll find a map for a very similar engine to yours. I've posted a map for a 3.0 with DC20 cams and EFI. I spent a lot of dyno time working on that ignition map, you're welcome to use that as a starting point.

Okay I get it now. The 5deg mark is after Z1 mark, which means that it is reached before TDC turning clockwise. I got it running pretty well now. Just for confirmation, with the advance line plugged in, the Z1 mark should be seen shift clockwise with timing light, adding more advance to the initial 5 degrees, correct?

Aurel