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914World.com _ 914World Garage _ Vacuum Advance Unit ID #

Posted by: kkid May 7 2010, 02:37 PM

Hello guys,

I have a '74 2.0 Djet and recently realized that a number on the vac advance actuator arm is none of those listed on the Dr.914's book(Page79).The book states:

603: 74-76 2.0

However mine says 979. I am wondering if my car had a wrong one at some point and I will have to look for an exact match or I can drive as is.
Attached Image

Also while ago I have seen a vac unit sold for 914 which had a 4 digit number 2XXX on the actuator arm. IIRC it was a Bosch unit.

My car runs OK now but if there is an area I can improve I would like to try.

Thanks for in advance

Posted by: tod914 May 7 2010, 03:20 PM

I noticed the replacement ones have four digits. They also don't have the nut on the canister with the white paint mark. I think my 73 2.0 had a 979 on it. I just replaced it with the proper one. I believe 979 would be for a 1.7. I'll double check later for you.

Posted by: dr914@autoatlanta.com May 7 2010, 03:35 PM

979 does not exist so probably a bosch unit provided to the factory for original distributors. The bosch correct number should be the 603 for the 74 2.0 cars, the three representing the last three digits of the original long bosch number 1 237 122 603 73 2.0 used originally the 601 on the arm numbered vacuum advance which was 1 237 122 601 The difference is in the way they advance and retard according to the way the engine is set up. For optimum performance in stock dress install the called for vacuum advance.

QUOTE(kkid @ May 7 2010, 01:37 PM)

Also while ago I have seen a vac unit sold for 914 which had a 4 digit number 2XXX on the actuator arm. IIRC it was a Bosch unit.

My car runs OK now but if there is an area I can improve I would like to try.

Thanks for in advance

Posted by: kkid May 8 2010, 06:02 PM

Thanks to both of you tod914 and George for the input. You guys are amazing walking 914 encyclopedias. I think what I saw had a #2603 instead of #603 and IIRC it did not have a nut on it. Wondering if these are readily available.

Now I am sure I have a wrong one on my car. Thanks PO. You can have my

While I am finding a correct vac can, this afternoon I took it out to see if it is in good condition. I connected vacuum pump on each port at a time. Then what I found was the retard port(thicker one) did not hold vacuum thus the arm moves back as it leaks. Funny thing is my car has been running pretty well with this unit. Is the vacuum unit really necessary? I know that the advance port is not used on '74 car.

Anyhow, I have spare 979 which holds a vacuum on the retard port. So I installed it. Now the car dose not want to idle right. The idle screw and mixture knob don't really want to cooperate. I mean it's got much harder to adjust than before. I only can adjust the idle around 1100-1200rpm at lowest. If I try to go lower it gets to around 8XXrpm but it pings and the car quakes. Oh, this spare 979s' nut looks to have been adjusted at some point since white paint mark is missing.

What should I do now?

I guess I should put the old one back in but I really want to make the vac can work.

Thanks for reading. Any advise would be much appreciated.