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.