Replacing stock intake manifold with Edelbrock 3711 manifold. Moving over the fittings and need to know what this is? Other problem I'm having is stock location was on the rear passenger side, however it's a 1/2 inch fitting and the 1/2 inch port is now on the driver side rear. The passenger side rear is a 7/8 inch fitting. Do I just move it and then plug the 7/8 hole with a pipe plug? Pic of the item is attached, anyone know what it is?

 

I'll let others go into more detail on the exact function of that part, but my understanding is that it stops the flow of coolant going into the heater core when the AC is on.

Since my car has the AC removed, I put in this:
https://www.yearone.com/Product/1964...lass-442/hhf71

Edited to add,
I also installed an Edlebrock Performer intake.

 

Thxs midrange. I appreciate the info. I still have factory AC so I'll want to keep that. I guess I'll have to extend my heater hose to now reach the other side of the manifold since the 1/2 inch port of that part is now on the driver side. Anyone know of any issues with a heater hose running that close to the distributor?

 

How about a 7/8 - 1/2" reducer?

 

Any idea who has them in stock? I looked for similar parts at some of the bigger box stores but no luck. Any of the sites like Summit, YearOne, OPGI, etc have them?

 

I got a pretty blue one forms Earl's but you can get a standard reducer from any hardware or pluming store.

 

The 1/2" to 7/8" bushing from a hardware store would work fine for you. I'd go with a brass one rather than black iron tho', IMHO, brass would look better on the fresh aluminum intake.

Just be very careful when you tighten them, it's pretty easy to over do it, and crack the intake.

 

Or stainless steel. Use some pipe thread sealer with teflon on the threads.

 

This part is called a "heater control valve" and it should screw right into the right rear of that intake.

 

Aren't there two different size heater valve threads depending upon the year of the engine?

 

According to Year One, there are two sizes, one for '64 to '70, and a larger one for '71 to '72.

https://www.yearone.com/Catalog/1964...cooling/heater

 

I don't think the 2 heater valves are interchangeable. IIRC the '70 and earlier valves have a reverse operation from the '71 and later valves. Similar to an electrical switch one is normally open and the other is normally closed. I put a '70 manifold on my '71 and used a '70 heater valve. It worked in reverse of what I expected (it flowed hot water when the temp setting was set for colder temps). It's been 20 years since I did this so the details are a little fuzzy, but I think I got a '71-'72 manifold from a junk yard and used the correct valve to get the heater to work properly.

 

it's a flux capicator! ditch the valve if your throwing a non stock intake on it. no worries in the long run.

 

You really dont need that ugly heat control valve in your engine compartment.I believe it just prohibits flow through the heater core, reducing warm up time, helping emmisions.
You can buy the nipples at any parts store, and hook up your hoses directly, deleting that ugly heater control valve.

 

The heater control valve shuts off flow to the heater core (under the dash) when you're running the air conditioning. Otherwise you'd be heating and cooling the at the same time, which is not very efficient.

 

Yep, that's what I thought.

You are correct about the valve operation, but I was referring to the thread size only. Edelbrock has to make the manifold work with either valve, so they make it with both hole sizes. If the user wants to put the valve in the original location (the larger hole), he can install a bushing. If EBrock made it with the small hole on that side, it would be hard for the user with an early engine to drill it out to the larger size.

 

That makes perfect sense. Why stock 2 different parts when you can make a universal part that fits 2 applications.

 

Not completely correct. The heater control valve only shuts off the coolant to the heater core when the A/C is on the MAX setting or on full cold temp. It opens up at other times to allow you to dial the exact temperature you want. The actual temperature control is not done with this valve, but with a flapper valve inside the HVAC box under the dash. Shutting the coolant flow is just done to maximize the A/C, but the reality is that you can eliminate the heater control valve and the A/C will still work fine (unless you live someplace like Phoenix).

 

I guess the problem I had with my '71 cutlass using a '70 intake manifold and heater valve was no heat because the valve was only open when the AC was set to MAX.