2.7 Questions

[Matt in Japan]

I'm new to Porsche and I'm still learning a lot about specifications and basic maintenance. Currently, I'm working out of a Haynes manual until I get some better references on order. Haynes gives me several different timing and dwell angle adjustments, depending on whether the car is California, 49-state, or UK model. My VIN is 9117301446 indicating a rest of world model according to some resources I found on the internet.

What are the correct dwell angle, point gap, and ignition timing settings for my car?

Thanks to anyone who can help out.

Matt
1977 911S

[ChrisBennet]

Some or all of the those setting may be on sticker in you engine compartment.
-Chris

[RoninLB]

might want to try to set point gap at .35mm without a dwell meter.. recheck after 500mi, 3,000mi.. don't put a dwell meter on the coil

might want to try disconnecting dizzy vac permanently and set total for 33deg-35deg.. then whatever the initial timing falls to is your new inital spec

I would confirm that the fuel mix is correct

listen for low rpm pinging.. if so then reduce total timing 2deg and see what happens

[Jim Sims]

Matt, According to my 76/77 technical specifications book you have a 1977 911/911S Japan 2.7 liter model. That's what the 3 means (Japan) after the 7 in your VIN number. Your car's a coupe also.

Ignition timing at 80 degrees C oil temperature: 15 plus or minus 2 degrees ATDC (after top dead center) at 950 to 1000 rpm with vacuum hose attached to distributor. There is no timing advance listed for higher engine rpm's.

Dwell for Bosch distributor: 38 plus or minus 3 degrees or 0.35 mm point gap; for Marrelli distributor 37 plus or minus 3 degrees or 0.35 mm point gap.

Spark plug: Bosch W225 T 30 or Beru 225/14/3 with 0.7 mm gap

CO: 1 to 2 % at idle speed; detach hose at auxiliary air pump and plug if CO level is to be tested or adjusted.

I also have the factory illustrated parts catalogs for 1977 if you need any Porsche part numbers. Cheers, Jim

[RoninLB]

Originally posted by Jim Sims

Ignition timing at 80 degrees C oil temperature: 15 plus or minus 2 degrees ATDC (after top dead center) at 950 to 1000 rpm with vacuum hose attached to distributor. There is no timing advance listed for higher engine rpm's.

Yep, Jim is correct... if you believe the book is logically correct.. some guys feel that the sudden smog requirements on the '77 2.7 did a beating on the engine.. among them is the dizzy vac unit and tune-up specs... which usually results in the engines running poorly, and hotter at idle and lower rpms.. emissions control devices were primitave in '77............Ron

[Matt in Japan]

I appreciate the fast responses! A few questions:

1. Sorry for what seems like a dumb question, but does "dizzy vac" mean the distributor vacuum advance line? I'm not familiar with that term.

2. Can I set the timing with the vacuum advance disconnected?

3. This is the really dumb question. Does ATDC mean that the plug is firing after the piston is on its way down? I always assumed that optimum timing would be somewhere close to TDC. I'd like to understand more about why it works this way.

Thanks again...

Matt
1977 911S

[Evans, Marv]

Matt:
Order the 101 Projects for your Porsche from PP & Wayne's rebuild book when it comes out.

[Jim Sims]

I thought the timing was a bit extreme too. The '77 California specs have the same timing values as the model for Japan. However, the 49-state USA model is listed as TDC plus or minus 2 degrees at 950 to 1000 rpm. The '77 ROW is listed as 5 degrees ATDC at 900 rpm. All specify the vacuum hose be attached to the distributor.

Dizzy vac=vacuum hose to distributor vacuum advance. The advance only operates at idle. Yep, ATDC means firing on the way down on the power stroke. Jim

[RoninLB]

Originally posted by Jim Sims
However, the 49-state USA model is listed as TDC plus or minus 2 degrees at 950 to 1000 rpm.

actually Jim, the vac was plugged when delivered......... Ron

[Matt in Japan]

Two correct replies meaning that I can set it with or without the vacuum line connected? If so, does anyone know a good setting with the vacuum line disconnected?

Bottom line is I tried to set it before, line connected, and it ran erratically. I disconnected the line and it ran great, defying logic as set forth in Haynes. I checked the timing again, and noticed that the marks were close to TDC, once again defying Haynes. I noticed a slight miss, so I wanted to go back and tweak a little more, but not without good advice.

I'm going to put both of Wayne's books on order, and I appreciate everyone's help in the interim.

[RoninLB]

Two correct replies meaning that I can set it with or without the vacuum line connected? If so, does anyone know a good setting with the vacuum line disconnected?
---Matt.. read my 1st reply again

Bottom line is I tried to set it before, line connected, and it ran erratically. I disconnected the line and it ran great, defying logic as set forth in Haynes. I checked the timing again, and noticed that the marks were close to TDC, once again defying Haynes. I noticed a slight miss, so I wanted to go back and tweak a little more, but not without good advice.
---Matt.. read my 2nd reply again

I'm going to put both of Wayne's books on order, and I appreciate everyone's help in the interim.
---Matt.. you smart.. and Wayne's parts catalog is a great resource.. enjoy

[Jim Sims]

Ron is right. It's a vacuum retard unit; retards 10 degrees only at idle. If the retard is working as soon as you disconnect it you should see a timing advance of 10 degrees. If you were set at the ROW setting of 5 degrees ATDC then it should change to around 5 degrees BTDC when you disconnect the line. Matt, you could do as Ron suggests and leave the line disconnected and set for a total (mechanical) advance of 33 to 35 degrees at 6000 rpm. Then whatever the timing reads with the hose disconnected when you go back to idle is what you'll use for future checks of timing at idle. Are you using the Z1 mark for TDC? Do you have the dwell set correctly? The miss could also be a fouled plug or bad or loose plug wire. Cheers, Jim