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73 intake water system


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I had similar questions when I converted my 260 from weber DGV's to round top SU type carbs. Here is what I learned about the plumbing.

The hoses are there to help the intake and carbs warm up faster in the morning by running warm radiator fluid through them. I imagine the lines also help keep the intake and carbs at a more or less constant temperature when the engine is warm.

The later carbs (found on the '73 and '74 models) had three radiator fluid lines, two through the intake manifold, and one through the carbs. The '70-'72 models only had one line that ran through the intake. Therefore, whoever converted your car to the earlier carbs just connected the thermostat housing to the water valve, since the connection at the carbs was no longer there.

To convert to the earlier carbs, I:

1. Replaced the gooseneck with three openings (as shown in the second picture on your site) at the thermostat with a brass nozzle (from Ace Hardware ~$2).

2. The lower hose at the water valve at the back of the engine was threaded, so I capped that off with a brass cap (again from Ace).

3. I removed the smaller diameter pipe that ran under the intake.

4. I hooked the new nozzle up to the larger diameter pipe on the intake.

This basically replicates the earlier round top setup. I didn't have a problem for the short time I used it (long story), but it doesn't get very cold here.

HTH, and post back if you have more questions.

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Two more things I remembered:

1. The smaller diameter line through the intake is part of the EGR system. When the fluid is above operating temperature, the valve doesnt open, and this cuts off the EGR circuit. Thus, if you want to keep the EGR system going, you need to split the line out of the thermostat housing and hook up the smaller diameter line at the intake.

2. The larger diameter hose has a different diameter at the thermostat housing and at the intake.

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yes you helped me a great deal. I have a couple manuals and they did seem to tell me wht i needed, but u did. It all make sense now. Im pretty much going to do the same as u. I did have a couple questions though. The water valve u capped off, does this shut the water down after operating temp is reached? Or am i gogint to always have water going through the intakes? Also about the erg system, someone has taken out the smog pump and various items but i dont know what still is working. I dont think i need the erg anymore but not sure when i switch my hoses around if i should leave it intact.Let me know thanks.,


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1. Water Valve

This valve shuts off once the engine is at operating temp (somewhere around 105F). Thus, there should not be constant flow through the intakes.

2. EGR

In general, I prefer leaving smog equipment hooked up, however, since you have the roundtop carbs on the car, I don't think the EGR system will be hooked up.

The EGR solenoid valve has a vacuum line to the rear flattop carb for the vacuum signal, so if the valve is blocked off, or otherwise not connected to intake vacuum, the EGR system isn't functioning.

I'd say that the overall approach for dealing with the smog equipment is just to make sure that you don't have vacuum leaks, which will wreak havoc with the way the engine runs.

Have fun.

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