74 450SL distributor vacuum help needed

[halw540]

This post under SL is a copy of the question under Vintage in hopes of getting help. I am working my way through issues on a '74 450SL I just purchased (93K miles) and do not have a service manual.

Problem - I have no vacuum to my distributor at any rpm/engine temp. On the throttle valve are two 1/8" vacuum ports - one on the front and one on the rear of the body. The rear port, where it is plumbed, shows no measurable vacuum. The front port shows 14" to 18" vacuum depending on rpm. I assume the front port is where it should be plumbed to??

Second distributor vacuum problem. The switch over valve, between the distributors vacuum source and the distributor, is not opening at any temp/rpm. What activates the switch over valve? How can I tell which is defective?

Thanks in advance, Hal

[halw540]

For anyone chasing this type of problem one of the members referred me to this site - I was able to solve the problem.

'74 450SL... wrong distributor?