Jump to content

1973 620 L16 Manual Vacuum Diagram


Recommended Posts

Hopefully I didn't miss this in my searches, but I'm trying to find a vacuum diagram for my 73 L16. All I've been able to find is one for a 78 L20, which is a great thread, but not the same carb as my 73 620. I'm chasing I rough idle, (not bad, and got better with idle mixture adjustment and other hints I got from the forum, thank you!) and I see the PO replaced some vacuum lines with soft yellow tubing and capped one of the lines off from the base of the carb. I'd like to make sure things like my vacuum advance are connected to the proper spot on the carb and elsewhere and not switched around to the wrong vacuum source. Thanks in advance for any help the forum can give!

Link to comment
  • Replies 3
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

There will be a hose from the valve cover side of the carburetor base to the vacuum advance on the distributor. Make sure that is functioning. Pull distributor cap off, pull hose off the carburetor end and suck on it. The rotor should turn clockwise about an inch. It should hold position till you release it. If so, presume it to be working. 

 

There will be a vacuum hose from the left side of the intake below the carburetor up to the ATC (automatic temperature control) on the snorkel on the air filter housing. Pinch closed when idling. If it improves then there is a leak in it.

 

There will be a garden hose size vacuum hose from the large metal pipe sticking out between the exhaust manifold to the PCV (positive crankcase ventilation) valve mounted on and below the left side of the carburetor on the intake. While it should be connected it won't affect running. Pull PCV valve and shake it. If it rattles presume it's working.

 

On the rear of the two intake runners is a fitting with a finger sized hose to the brake booster. Pinch the intake end closed. If idle improves there may be a leak in the hose or the booster has a vacuum leak.

 

You don't say, but if you have an automatic there is a small hose and metal line from the fitting on the intake for the booster that goes to the modulator valve on the automatic. Again, pinch closed and if the idle improves there is likely a leak. You need this functional as this tells the transmission the engine load and up shift points.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.