75S 2.7 Timing Question

Rob Chamberlain · 08-10-2009, 04:10 AM

I'm working on a 2.7 (75 911s) and to achieve ignition timing @ 5 degrees ATDC I find that I have to move the distributor as far as it can in the slot (to the right).

The points gap is set to .012 and advance looks ok. I'm not sure of the dwell but given the CD I'm not sure how critical this would be and that it would really make much difference anyway with respect to the position of the distributor.

Just doesn't seem right that it would be so far over in the slot. Just curious if anyone else has to go 'as far as it can go' to achieve correct timing.

Thanks for the help.
Rob

Walter_Middie · Walter_Middie's Garage

Rob,

The position of the distributor can be different depending on how your car is set up. For instance, on my car (75 S) the previous owner had moved the plug wires one position off, and compensated by installing the distributor a couple of gear teeth off. The distributor worked great, but wasn't installed "correct". I changed everything back to how it should be, but it didn't change how it ran.

If you don't have enough room to rotate your distributor any more, your can re-index it by simply pulling it out and rotating the distributor drive gear one tooth while re-installing it.

The idle timing is OK to just get it started, but you really want to set the timing at 6,000 RPM. You can do this by holding the timing light with one hand and quickly reving up the engine with the other. You'll see the timing marks advance with RPM and then stop. Where the timing stops is your total timing, and should be between 36 and 38 deg BTDC.

Flat6pac · 08-10-2009, 04:46 AM

There is 12 cogs on the bottom of the distributor to drive six cylinders. If youre too far one way on the setting you should be able to move one cog and bring you into the area you want to lock in

Rob Chamberlain · 08-10-2009, 04:51 AM

Got it. I will give it a shot and check the timing at 6k to see if it is within spec.
Thanks for the responses, it's great to have this board (and it's members) to turn to for help.

Thanks!
Rob

wowzer911 · 08-10-2009, 05:05 AM

You should get some assistance from someone to rev to 6000 rpm's, as it's tricky to keep your eye on the tach and the timing light at the same time.

Walter_Middie · Walter_Middie's Garage

Quote:

You should get some assistance from someone to rev to 6000 rpm's, as it's tricky to keep your eye on the tach and the timing light at the same time.

The distributor will quit advancing before you get to 6000 RPM - that helps when you are doing it yourself. Just rev it up till it quits advancing. This will also keep you from holding it at 6000 RPM needlessly, while you try to adjust the timing. With a quick rev, you can get an idea of what the total timing is. Then, while its idling, adjust the timing to where you think it should be, and try the rev again. It's a little trial and error, but I usually get it right after only a couple of tries.