The proper port for that vac signal is the port torwards the rear of the car, closest to the airbox. This gives a signal only at idle.

The vac line should have no "splitters"...meaning it's specific only to the distributor.
If you have it tied to the ports facing the front of the car you are getting vac at the wrong time.



BTW you should think about eliminating the Vac as I have suggested. Your engine will thank you for it.

Really??. . .I thought you were just talking about while adjusting timing. I see what you're saying now. TUR-HUR, that's what I get for trying to work while I'm learning about more important things!!

This shows another one of my ignorant sides. Is vacuum advance only an emissions component? What are the effects of elimination?

And BTW . . yup, just confirmed it. It is connected to correct port on TB (the port that is AFTER the plate) however it is split with one side going to dist. advance and the other going to a factory switch (as it's controlled by the factory harness) that in turn goes to the WUR.

I'm thinkin' I think the way you like Aaron!. . . I'll pull that from the dist. side and plug, leave the switched line going to the WUR in place as I do see this in some vac. diagrams. . .then set at 0. That'll have to do for now until I can get my 6k marks.

Now, should I be 30 BTDC or 35 BTDC on 6k for an emissionless 2.7 CIS? Everytime I've seen this spec it's been for mechanical or carb'ed.

Mostly, Your distributor is Vacuum RETARD, which is to pass emissions @ idle. Not performance oriented!


If you set the system rich, then you can shoot for 32-34. Which should be about 2-4 BTDC. If you go to carbs, you can get more aggressive. Be conservative with timing with a CIS system.

As far as the Vac for the CIS Here is a 75 for reference;
Distributor
http://forums.pelicanparts.com/uploa...1276213742.jpg

Plumbing for the WUR.
http://forums.pelicanparts.com/uploa...1276213852.jpg

Talked with a tech, 5 deg BTDC no problem.

Aaron,

Thank you, Thank you, Thank you, Thank you!!

And thank you Frosty for turning me on to Aaron, and honorable mention to Bill too for touching on the same issue.

I deleted the vacuum advance. The most I could get this way without running into the stumbling issue at a constant 3k (my typical highway) was app. 3 ATDC. (BTW, I set points back to .012 damned the dwell, which mow comes in at app 30) However from what I saw with the little time I spent with it last night 5 BTDC would be fine at idle up to app. 2k. I'm going to keep picking nits with things next week simply because I can :rolleyes:

Could be weak springs maybe??

ANYway, this solved the stumbling problem 100% as well as any decell rumbling/popping.

I'm still not willing to run this thing up to 6k and spin it unloaded :eek: I still just don't believe! Wouldn't it be much better to pull the dist. and have a setup to spin it at 3k? My stomach just turns at the thought of performing this with the engine free spinning. . . . "Rod, . . .meet my valves please sir. I'm sure you'll end up getting along nicely"

Just for the S&G's of it all I'm going to verify valve timing again, check the injector balance, then I'll check the CO (slightly rich you say?) then back to advance (curve) thing. Maybe I'll let Storz do the 6k when I have them check CO since I'm such a panzy ass with a weak stomach.

I think you're wrong about this - spinning it up unloaded is easier on it than spinning it loaded. It may be easier to over-rev unloaded - but 6K isn't going to hurt anything except your relationship with the neighbors.

I line up my timing light at idle, then reach over and quickly rev the engine then let idle again. If you are watching the timing marks, you'll see them advance, then stop at max advance. This max advance is what you are looking for. The engine is only reved briefly. Reset advance at idle if needed, and try the quick rev again to see if max advance is where you want it. It stops advancing somewhere before 6K, and it's not important to be right at 6k - only to see where the advancing stops.

This makes much more sense than what I was envisioning. I was thinking of pulling it to 6 and holding it for 2 -3 seconds.

So. . . somewhere say after 5 or 5.5 but before 6?. I'll look at that.

What I'm wondering now (since I couldn't go to 5 BTDC as Aaron suggested without hitting issues at 3k) is if the springs may be weak allowing it to advance too soon. I'm sure this test will tell me, especially if I hit max at 4k or less.

BTW. . .what's the full mechanical on the BOSCH for the 2.7's. . . 30 exact??. . ..anyone know?

Thanks Walter. . .it's an old holdout from muscle days. I was telling an old Mopar friend about this and he freaked too.

:D:D:D:D:D They're young, they'll live. SmileWavy

I wouldn't base any troubleshooting on whether you hit max advance before 4k or not. There's a good graph on here somewhere that shows what your advance should be as a function of RPM, and where it should max out. I measure mine at every 1000 RPMs and compare it to this factory spec. Mine is very close - but then I made it to be that way by changing springs and trial and error.

Looking for that now.

Thanks again!

I'm just adding some links here from former posts providing advance curves. This isn't a complete list from here and these may are may not be specific to the 2.7 911S, but just putting them all here in one place for reference. If others so desire please link others into this thread.

http://forums.pelicanparts.com/porsche-911-technical-forum/400609-distributor-compatability-71-t-e-s.html

http://forums.pelicanparts.com/porsche-911-technical-forum/236856-i-get-full-mechanical-advance-3000rpm.html

http://forums.pelicanparts.com/porsche-911-technical-forum/436417-distributor-idle-woes.html

http://forums.pelicanparts.com/porsche-911-technical-forum/455502-advance-curve-marelli-911t.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/443195-what-distributor-curve-rs-motor.html

http://forums.pelicanparts.com/porsche-911-technical-forum/484496-eliminating-vacuum-distributor.html

Adding info on CIS mixture settings:

http://forums.pelicanparts.com/porsche-911-technical-forum/170802-cis-info.html

http://forums.pelicanparts.com/porsche-911-technical-forum/185981-cis.html

http://forums.pelicanparts.com/porsche-911-technical-forum/212120-adjust-mixture-now-i-have-tool.html

Adding info on CIS testing:

http://forums.pelicanparts.com/porsche-911-technical-forum/118631-cis-fuel-test-pressure-question-77-2-7-a.html

From RoninLB:

"system pressure should be 4.8-5.2 bar. control pressure
3.4-3.8 bar. control pressure starts low, like 1-1.2 bar and goes up
to the top range in just a few minutes. if the w/up reg had power to
it for very long, it would have started to warm up. if you had
excessive control pressure on cold starts, the engine would be very
cranky for a few minutes, until it warmed up a bit. CIS gauges won't
allow the engine to run very well if the lever is in the system
pressure mode. the system pressure check is done quickly, and then
the lever is turned to the control pressure mode. system pressure
stays the same, control pressure rises. a "fix" can be attempted.
notice the 1/4" wide, round, depressed spot on the top surface of
the WUR. it's actually the top of a pin in a hole. if you can
depress it a tad more, the cold mixture will be richened. with the
gauge attached, engine cold, and WUR plug pulled off, so it doesn't
warm up, use a hammer and punch to move it just a few thousandths
deeper. watch the gauge as you try tapping it down kind of gently,
because if you go too far, and make it too rich, where it surges.
shoot for 1-1.2 bar. (search for "adjustable warm up regulator").
before you do that, follow the top vacuum hose to the thermo-valve,
just above the left valve cover, over cylinders 2 and 3. the valve
needs to be closed when cold, so the WUR can run richer cold. when
it opens, vacuum reaches the WUR, and it goes leaner. the hose
should not have vacuum when cold, until the t/valve warms up. check
for power and ground at the plug on the valve."

Okay. . . so here's the distributor(s) I have. . . .both of 'em. .

http://forums.pelicanparts.com/porsche-911-technical-forum/183144-distributor-id-2-7-a.html

Now, I finally got my service manuals and they do have the curve graphs. I'm assuming this dist. is for the '77 and Ca. cars.

Looks like it's off to Aaron for recurve time. Anyone just wanna trade for one off a '73? LOL

(Aaron. . .I may wait on this to see if I get SC grind cams in there. If so, I'll take it to dyno and get the data to you with the dist. . . . no sense doin' it unless I do it right.)

Why can't we just buy springs and weights anymore for stock profiles anyway?? If I recall I was always able to do this from PAW for US muscle. Are suppliers simply getting out of the market with electronic and distributorless ignitions??

ANYway. . .thanks to Aaron I'm still running 150% better.

BTW Kodi. . .haven't forgot about you. . just a crappy weekend here (35 F and rain). I'll check those injectors this next weekend.




OH. . . and also. . .when I was checking out advance vs. RPM the other day. . .noticed that my timing seemed to be jumping +- a few degrees, but dist. was given okay (and has no shaft play). . . I'm looking deeper here too.

Ain't it great being A/R and O/C at the same time :D

Let me know when you are ready.

The 184 series of dizzies are great. They hold their respective curve and rarely exhibit excessive wear. The 007 is a fine base to start with. Bosch has never been too excited in supplying parts for Distributors. I had to make up a batch of custom springs and other parts to maintain to keep going.