how much does your vacuum retard line retard your timing.

[lonewolf]

80SC
manual says to set timing with both lines off and plugged.
set timing to 5BTDC but when lines are hooked back up timing ends up at 5ATDC

All the threads i've read say after hooking up lines timing should remain at 5BTDC.
If the retard function is working then how can that be ?

[porsche930dude]

I doubt anybody will give you a straight answer on this but id love to know myself. From what iv read the timing is suposed to be about 7btdc with the lines connected but it can be different from car to car so its considered irrelevant. My car idles crazy high when i disconnect and plug my lines so iv got it set at 5 degrees with the lines connected. As to why it idles high disconnected is another question i havnt been able to answer

[cab83_750]

Originally Posted by porsche930dude

I doubt anybody will give you a straight answer on this but id love to know myself.

+1 subd.

[lonewolf]

Originally Posted by porsche930dude

I doubt anybody will give you a straight answer on this but id love to know myself. From what iv read the timing is suposed to be about 7btdc with the lines connected but it can be different from car to car so its considered irrelevant. My car idles crazy high when i disconnect and plug my lines so iv got it set at 5 degrees with the lines connected. As to why it idles high disconnected is another question i havnt been able to answer

Hey porschedude. i have one of your timing thread saved already.
first to answer your question .when you unhook the retard line the timing increases causing revs to go up.

[911Freak]

+1 sub'd

Just went thru this Monday.. I found that I got the most consistant results when I timed the car at 5BTDC with both lines unhooked and NOT plugged...this resulted in nearly identical timing after hooking up the hoses...+-1.5-2 degrees with the old eyeball

I don't know if the advance & retard is working properly, hence my sub... I will say that when both lines were off, as I was setting up the timing lite I plugged the retard line with my finger just to see what would happen and she nearlly stalled...so I assume the retard vaccum is working properly...

I have a Snapon lite but don't have the dial function on the lite...

[lonewolf]

porschedude.
by you setting to 5btdc with lines connected you may be in trouble depending how many degrees your retard function does. I'll use mine as an example. my retard hose retards the timing 10degrees. if i set timing at 5btdc with hoses on as soon as i open the throttle the retard function is gone and i'm instantly at 15BTDC ,then add 20degrees mechanical advance, then the vacuum advance and you will be beyond 35degrees.

[lonewolf]

Originally Posted by 911Freak

+1 sub'd

Just went thru this Monday.. I found that I got the most consistant results when I timed the car at 5BTDC with both lines unhooked and NOT plugged...this resulted in nearly identical timing after hooking up the hoses...+-1.5-2 degrees with the old eyeball

I don't know if the advance & retard is working properly, hence my sub... I will say that when both lines were off, as I was setting up the timing lite I plugged the retard line with my finger just to see what would happen and she nearlly stalled...so I assume the retard vaccum is working properly...

I have a Snapon lite but don't have the dial function on the lite...

when i shine my timing lite on and uhook the retard line i go from 5ATDC to 5BTDC put back on and back to 5ATDC

[911Freak]

Quote
lonewolf:
when i shine my timing lite on and uhook the retard line i go from 5ATDC to 5BTDC put back on and back to 5ATDC



BTW good advice about short cutting and setting timing with lines on....

[lonewolf]

Originally Posted by 911Freak

Quote
lonewolf:
when i shine my timing lite on and uhook the retard line i go from 5ATDC to 5BTDC put back on and back to 5ATDC

Exactly, I think.. mine too...

BTW good advice about short cutting and setting timing with lines on....

Exactly mine too. Are you sure? I thought you said you set timing with lines unhooked and then put lines back on and had almost the same timing.
I have a 10 degree swing in mine

[911Freak]

Woops your rightI missed that, sorry bout that!

I only have a swing ove +-1.5-2degrees which is far from the 10degree...

Good catch, I'll edit that out so no one is mislead, Thanks!!

[T77911S]

Originally Posted by lonewolf

porschedude.
by you setting to 5btdc with lines connected you may be in trouble depending how many degrees your retard function does. I'll use mine as an example. my retard hose retards the timing 10degrees. if i set timing at 5btdc with hoses on as soon as i open the throttle the retard function is gone and i'm instantly at 15BTDC ,then add 20degrees mechanical advance, then the vacuum advance and you will be beyond 35degrees.

+1
if you dont see a change between vacuum lines connected and disconnected, most likely the diaphragm on the distributor is bad. set the timing to spec. check and see if you are getting full advance. my 77 is 0deg with vac. connected. i believe the different timing settings is because of the different cam timings used. the sc's used 3 different cam settings.

[psalt]

lonewolf wrote,

80SC manual says to set timing with both lines off and plugged.
set timing to 5BTDC but when lines are hooked back up timing ends up at 5ATDC
All the threads i've read say after hooking up lines timing should remain at 5BTDC.
If the retard function is working then how can that be ?

lonewolf,

What you have read is incorrect, the vac retard is an emission control device to help meet the HC curb idle test. It uses manifold vacuum and should retard the idle timing 5-7 degrees when connected. The timing should be set with both lines disconnected and plugged and the idle reset to 950 rpm. After you set the timing and reconnect the hoses, you need to reset the idle speed to 950. I prefer to leave the vacuum retard plugged and set the timing to 7 BTDC. The vacuum retard causes the engine to run hot at idle and cold starts are improved without it.

Paul

[lonewolf]

Originally Posted by psalt

lonewolf wrote,

80SC manual says to set timing with both lines off and plugged.
set timing to 5BTDC but when lines are hooked back up timing ends up at 5ATDC
All the threads i've read say after hooking up lines timing should remain at 5BTDC.
If the retard function is working then how can that be ?

lonewolf,

What you have read is incorrect, the vac retard is an emission control device to help meet the HC curb idle test. It uses manifold vacuum and should retard the idle timing 5-7 degrees when connected. The timing should be set with both lines disconnected and plugged and the idle reset to 950 rpm. After you set the timing and reconnect the hoses, you need to reset the idle speed to 950. I prefer to leave the vacuum retard plugged and set the timing to 7 BTDC. The vacuum retard causes the engine to run hot at idle and cold starts are improved without it.

Paul

Paul . I don't see how what i wrote is any different from your instruction.
I set timing to 5BTDC with both lines off and plugged at 950rpm. then reconnect lines , timing drops to 5ATDC and rpms drop to approx 4-500.I then open bypass to get back to 950 but the timing is still at 5ATDC. if what your saying is correct that the retard funtion retards the timing 5-7 degrees how can you ever end up at 5BTDC with lines reconnected up using that method?

[Gunter]

When I still had Lambda CIS on my '80 SC, I didn't notice any effect of the advance or retard when idling.
There just wasn't enough vacuum in idle; I set timing at 5deg @ 950 RPM and it stayed there with or without the vac lines connected.
Of course, as soon as it came off idle, the advance would add 5-7 deg immediately all the way up to 33-35 deg max.
I found with several SC-distributors that the maximum advance, mechanical plus vacuum, didn't exceed 33 deg in total.
My understanding is that the retard only comes in when you decelerate (Coming off higher RPM) but has no effect when idling. (That's wrong, it does have an effect)
I would start with servicing the distributor to make sure that it is good meaning: weights and springs and the vacuum can.
Plus, make sure that the lines are connected properly at the TB: above and below the throttle plate respectively.

[911pcars]

I would have to agree with Paul.

The purpose of the vacuum retard is to .... retard the ignition timing at idle for emission purposes. Once off-idle, the vacuum retard should have no effect other than defaulting to the mechanical advance curve within the distributor. Thus, at idle with the vacuum diaphragm connected, the timing should occur ATDC (retarded) and BTDC w/o the diaphragm connected.

Just wondering, how many vacuum ports are on your diaphragm?

Sherwood

[SC-targa]

From 1980 to 83 the 911 SC's had a vacuum advance and vacuum retard, so two ports on the diaphram.

Specs are 8-12 degrees vacuum retard and 3 to 7 degrees vacuum advance.

Regards,

Jerry

[lonewolf]

Originally Posted by SC-targa

From 1980 to 83 the 911 SC's had a vacuum advance and vacuum retard, so two ports on the diaphram.

Specs are 8-12 degrees vacuum retard and 3 to 7 degrees vacuum advance.

Regards,

Jerry

thanks, specs are 8-12. those were the numbers I was hoping some would post.Where did you find them?
i'm right in the middle so nothing wrong with the whole retard part of my system.

as soon as the throttle plates opens a CH the retard vacuum drops and I'm immediatley at 5BTDC then with mechanical and vacuum advance I'm at 33BTDC .

no spec book or manual I've read mentions that once you hook retard line back up timing will go to ATDC and not to worry about it .
So really the timing for my 80SC is 5ATDC with all lines hooked up and working properly.

[psalt]

no spec book or manual I've read mentions that once you hook retard line back up timing will go to ATDC and not to worry about it .

That is because the spec is with vacuum disconnected. Vacuum retard uses manifold vacuum, which means full vacuum at idle, the emission test at the time was a curb idle HC test. If there is no difference at idle, your distributor is broken. Vacuum advance uses ported vacuum, no vacuum at idle, only at part throttle cruise to improve mileage. The retard line is usually grey or blue, the advance lines is orange, but I have seen them connected backward several times.

[lonewolf]

Originally Posted by psalt

no spec book or manual I've read mentions that once you hook retard line back up timing will go to ATDC and not to worry about it .

That is because the spec is with vacuum disconnected. Vacuum retard uses manifold vacuum, which means full vacuum at idle, the emission test at the time was a curb idle HC test. If there is no difference at idle, your distributor is broken. Vacuum advance uses ported vacuum, no vacuum at idle, only at part throttle cruise to improve mileage. The retard line is usually grey or blue, the advance lines is orange, but I have seen them connected backward several times.

paul .I have corrected my posts to avoid confusion.
my system is working EXACTLY as it should. nothing is broken .I was just trying to clear up some confusion for everyone like porschedude.
one point I was making was that in a lot of spec sheets . Look in the back of Bruce Anderson performance handbook as an example. It has all the timing specs for every year. For my year it says 5BTDC thats it .it says nothing about if the lines are connected or not. Not everyone has the large decal under their decklid which states lines dissconnected or the proper instruction manual. it is obviously confusing to some like the fellas who have posted above. If you read some other threads on timing you'll see that some say it should be 5BTDC with all lines hooked up and thats not right. some say there is no difference once you hook lines back up and like what you said if thats the case then your vacuum diaphram is broken or worn or the advance plate is sticking or a vacuum problem etc.basically something is not working right in the advance retard area.
If your ign system ,distr ,vac diaphram ect are all working correctly and you have proper vacuum and all lines are hooked up correctly the timing is ATDC not BTDC. at idle.

[mca]

In my case, my retard line only brings the timing down a couple of degrees. This indicates that my retard diaphram may be worn or broken. I set my timing at 7 BTDC with the retard line disconnected and plugged. When I reconnect the line, my timing moves to 5 BTDC.

I still get full advance despite the retard diaphram being out of whack - the retard nipple has wiggle.