911SOUK

I need help with my 3.0 transplant.

Should there be vacuum on the distributor at idle? Where does the line go /where is the distributor's vacuum source?

I found a vacuum source under the atmospheric connection to the WUR. The line to the WUR was hiding this from me until tonight. And it was sucking air up to now. I plugged it, but the motor ran with the same stumble and shaking at low throttle that I had before (I've been trouble shooting for too long). The two stubs are on the rear of the throttle body (toward the back of the car) at aproximately the 7 o'clock position. The top one is atmospheric pressure for the WUR, but the lower one is ??

This is where my 2.7 motor gets it's vacuum from. Should the 3.0 distributor connect here? I think the two motor types are different set ups (retard vs advance), but I'm not 100% sure.

I think the result of this error is my stumble and shaking at very low throttle input (just above idle). Bad ignition!!!


HEPL PLEASE!
<img src="confused.gif" border="0">

Jeff Curtis

911SOUK, you're right, it's either your vacuum advance -or- retard line that goes to that port on the WUR...the other one goes to the throttle body...ABOVE the butterfly I believe.

Sorry, can't remember which goes where, but FWIW, it won't make any difference that I could ever tell in performance or idle.

I eventually disconnected AND plugged the vacuum ports at the rear of the throttle body and WUR, no need to plug them at the distributor. This, I eventually did due to a supercharger installation because the car would always die under decel when cold...disconnecting both lines seemed to cure the problem.

When I sold my supercharger setup, I kept the ignition just the same, no vacuum advance/retard lines hooked up and it ran like a scalded dog!

I eventually went to an Electromotive HPV-1 setup...which had NO vacuum advance/retard settings, just RPM activated.

In summary, MY opinion is that you could just plug off the vacuum ports and chase down your idling problem elsewhere, some may disagree - but I've been there...and believe me, have I got some T-shirts!

911SOUK

Jeff, I have a vacuum source to the WUR already and the atmosphere goes to the top side of the throttle to compensate for barometric pressure supposively..(Jim Williams helped me correct this earlier)

Since I wasn't getting vacuum with my distributor connected to the port behind (toward the firewall) the throttle body, I have to conclude that the other vacuum port, the lower of the two in front (toward the rear of the car) should connect to the distributor. When I move the vacuum line to this port the vacuum does pull on the diaphragm inside the distributor. I can hear it spring back when I disconnect the line. The idle changes also.

So it looks like the vacuum at idle is doing something for my car. I just need to know if there should be vacuum to the distributor at idle. I don't want to make an incorrect assumption and then start setting the timing, only to find out later that it was the wrong course of action, or worst, damage something.

So the question for everyone tonight is: should there be vaccum on the distributor at idle?

Thanks,

Souk

Tom F

Which 3.0 distributor do you have? There are a couple of variations with a single vacuum advance connection and the '80-'83 US distributor with a vacuum advance and vacuum retard connector. There is a vacuum diagram for this latter unit, but you need to have the hood of the car from which it came to see it! So, I'd suggest that you find a manual to see how the vacuum hoses should be connected to the throttle body. However, I don't see the vacuum control on the distributor accounting for the kinds of problems that you describe.

911SOUK

Tom, I have a '76 S-model car with a '78 3.0 (recently transplanted). So no vacuum diagram, other than the one I have for the CIS system, but it does show the distributor in it. It is going back to the throttle body.

The big question is: Should there be vacuum on the distributor at idle, for retard?

My Bentley manual and all the other manuals, specify 5 degree BTDC with vacuum hose connected, and 26 degree BTDC without the vacuum hose, but at 6000RPM. This leads me to think that the '78SC 3.0 has vacuumn retard. So that would require there be vacuum to the distributor at idle.

If this is correct, my currect connection does not have vacuum at idle, and it may be part of what is causing my running problems (stumbles, pops and shakes under load and with small throttle input. I have a CIS pressure tester and alll new fuel delivery equipment. The fuel delivery seemed fine when I checked it last.

I'm still trouble shooting other items, but this is my current pain in the pooper.

Thanks,

Todd Holyoak

Souk

The 78 distributor has a vacuum advance so you don't want vacuum at idle. The ignition timing specs you quote don't require disconecting the vacuum line to test timing at idle since it will have no function. You disconnect it to test advance without the vacuum hooked up to test the mechanical advance of the distributor. This is from memory but if I'm wrong I'm sure someone will correct me.


Todd

Howard

SOUK,

BTDC is advance not retard. The term advance refers to ignition firing before the piston reaches TDC, so, 5 degrees BTDC is advance, as well as 26 degrees BTDC. The vacuum line on the '78 remains connected at idle (900 rpm 5 degrees) and at 6000 rpm, 26 degrees BTDC. If your vacuum unit on the distributor is working properly it will advance to to the proper setting at 6,000 rpm. You can locate a vacuum source actually anywhere in the intake runners,as close to the intake port as possible or if you go to carbs or MFI usually the intake manifolds.
As Todd said, this is also from memory, I'll check the book to confirm.
Good luck !

911SOUK

Thanks Guys. Looks like I should not be seeing vacuum at idle, and as my RPM's increase, I should see vacuum at the distributor. Right?

SO when I run the RPM's up to check timing without the vacuum line connected, this checks my mechanical advance.

So under normal operation and with the vacuum line connected, the system will work as designed. That is, the advance may or may not be at 26 degrees at 6000 RPM, but at some degrees affected in part by the vacuum. Correct?

If not, then what is the vacuum for???

<img src="graemlins/c.gif" border="0" alt="[ouch]" />

Thanks again guys,

Souk

Don.

Hi, this thread had been interesting to me, because I have a Euro 1978 SC, and I've been looking for the vacuum advance line on my car for years. The car seems fine but the gas mileage I get seems a little low (16 mpg overall/18 freeway), and I've heard that vacuum advance could be needed for part throttle efficiency, and better low rpm driveability.

At some point the PO replace the distributor with a new one. The new distributor has its vacuum advance nipple capped off. I've look at all sort of vacuum diagrams from Haynes/microfiche, but haven't been able to locate the vacuum advance on the throttle body.

I looked right below the WUR vacuum line on the throttle body as mentioned previously in this thread, but there's no nipple there. I've removed the CIS boot and looked all over the throttle body with a mirror, but there doesn't seem to be an extra nipple anywhere.

Could my Euro 78 SC not have an advance line? If so, do I need a different type of distributor? Or, could I just T off the WUR vacuum line?

Hey, thanks for listening.

-Don

'78 Euro SC Targa

John Adams

My 80 Euro SC distibutor has only one vacuum hose and it has no vacuum on it at idle.

Don.

Well that's interesting, since I believe US SC distributors are supposed to have two vacuum hoses from 80-83. My Euro '78, unfortunately doesn't have any hoses on its distributor, though it seems to have a place for one. I'm just worried that theres a hole on the throttle body sucking air...

-Don

'78 Euro SC Targa