Pagoda SL Group

W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: jeffc280sl on August 08, 2025, 22:47:02

Title: Venturi open ports
Post by: jeffc280sl on August 08, 2025, 22:47:02

I've owned my 1970 280SL with a 4 speed manual for over 30 years.  I'm changing the oil and noticed an open hose connector on the bottom of the venturi.  There are also 2 open connectors on the top of the venturi. One of these connectors is capped off.  I believe these connectors are part of the emission system.  Does anyone have a hose connection diagram for the venturi.  Thank you.

Jeff

Title: Re: Venturi open ports
Post by: TJMart on August 11, 2025, 20:07:10

Jeff,

Will you post some photos to show what you are talking about.

If so I will take photos of mine so you can compare and the forum can chime in as well to help you out.

Tony

Title: Re: Venturi open ports
Post by: jeffc280sl on August 12, 2025, 00:08:27

Hi Tony,

Thank you for you offer of help. 

Title: Re: Venturi open ports
Post by: jeffc280sl on August 12, 2025, 00:09:57

Thanks

Title: Re: Venturi open ports
Post by: jeffc280sl on August 12, 2025, 00:14:32

Tony,

I see we have the same year SL with 4 speed.  I've replaced components and modified/enhanced my car quite a bit.  I hope that someday I can return the favor of help

Jeff

Title: Re: Venturi open ports
Post by: TJMart on August 12, 2025, 16:56:25

Hello Jeff,

I took 3 photos to show you my setup. From what I could see from your first photo the open hose connector should be used for the water line coming from your warm running device on top of the Fuel Injection pump on the other side of the engine. The metal water line in your picture is connected somewhere else but I can't see from your picture where it goes.

The connector with the red cap on it should have a pipe that goes to the top of your valve cover. It is a vapor line that is for oil vapors to be burned by the engine via the venturi.
See second photo.

The bottom connector should have a 90 degree water hose that connects to a hard "T" pipe where one side runs to the lower radiator hose connected to the block and the other runs to the firewall.  See third photo.

You may have other questions.

Tony

Title: Re: Venturi open ports
Post by: jeffc280sl on August 12, 2025, 18:06:04

Thank you Tony.  I'll get back to you with any questions

Jeff

Title: Re: Venturi open ports
Post by: jeffc280sl on August 12, 2025, 19:22:54

Hi Tony,

On my car the hose from the WRD bypasses the venturi and connects back into the cooling system.  I think the purpose of the hoses is to preheat intake air.  Most likely this preheating is part of the emissions system. This seems counterintuitive because i always believed cold clean air is needed to produce power.  Same can be said for the hose coming from the valve cover.  This is emissions related as well.  My hose from the valve cover goes to a small plastic bottle under the venturi which collects any oil residue.  Basically my emission system has been completely bypassed as are the switches on the top of the transmission.  I guess I made these modifications 20+ years ago without creating any documentation.   My car runs great so I see no reason to change my setup.  Thank you very much for the photos.    I have a 123 ignition system so the emission boxes near the distributor are also disconnected.

Title: Re: Venturi open ports
Post by: rwmastel on August 12, 2025, 22:12:39

Quote from: jeffc280sl on August 12, 2025, 19:22:54

This seems counterintuitive because i always believed cold clean air is needed to produce power.

Right.  And if you're producing more power, you're probably running a richer mixture to use more fuel for that power.  More fuel means more emissions.