Bypassing 240Z heater

[rcv]

Has anyone had any experience deleting the heater core from the cooling loop?

While debugging some unrelated issues on my '70 240Z, my heater outlet hose decided to crack and start leaking coolant all over the place.  I had bought replacement input/output hoses a while ago and just never installed them because it seemed like too much of a pain.  That assumption was verified today - after a ripped cardboard glovebox, some busted knuckles and a half-removed blower fan I've decided this is a rabbit hole I just don't want to go down any further right now.  I live in Southern California so having a functional heater just isn't a big issue for me right now.

Here's my plan: plug the outlet elbow in the cylinder head with some kind of BSPT(?) plug, and then replace the "T" with just a straight piece of pipe or a coupler if I can find one. 

• Any reason this won't work? I figure this will basically be the same as having the heater valve closed as far as coolant flow is concerned.
• What size is the thread on that elbow? I've seen a few posts on here and hybridz, but none with a conclusive answer.  Z Car Depot has this 13/16" BSPT plug which they imply is the right part.

[siteunseen]

I looped mine with a hose. Easiest to connect one to the other. Lots of opinions so I fixed my asap.

 

Edited November 15, 2020 by siteunseen

[siteunseen]

Connect the elbow on the head to the Y under the spark plugs. You don't want the rear of the head dead, it needs to flow. I will suggest not romping on your car until the flowing starts, thermostat open. I've read stories of the core plugs blowing out. 

[rcv]

I was thinking about that too, but that’s dumping hot water from the head right back into the water pump inlet, right? Wouldn’t that make the engine run a bit hotter all the time? I’m keeping the intake warming piping, so I guess I’m doing that anyway. 
 

Something like this?

[siteunseen]

You are right. Mine was temporary so maybe you should plug them both.

I did it until my parts came in and honestly didn't drive the car. Let's see what the others say. I'm sorry for adding any confusion. 

 

[Zed Head]

52 minutes ago, rcv said:

Has anyone had any experience deleting the heater core from the cooling loop?

Here's my plan: plug the outlet elbow in the cylinder head with some kind of BSPT(?) plug, and then replace the "T" with just a straight piece of pipe or a coupler if I can find one. 

• Any reason this won't work? I figure this will basically be the same as having the heater valve closed as far as coolant flow is concerned.
• What size is the thread on that elbow? I've seen a few posts on here and hybridz, but none with a conclusive answer.  Z Car Depot has this 13/16" BSPT plug which they imply is the right part.

That's the typical way to do it.  As you said when the heater valve is closed those ports are blocked.

The thread size in the head is the same as the thread size of the block drain plug, under the manifolds.  That tells you very little unless you have a spare block.

[Zed Head]

33 minutes ago, siteunseen said:

Connect the elbow on the head to the Y under the spark plugs. You don't want the rear of the head dead, it needs to flow. I will suggest not romping on your car until the flowing starts, thermostat open. I've read stories of the core plugs blowing out. 

I think that the thermostat issue was in reference to the carburetor heating line, the one that runs to/from the thermostat housing.  We had a whole discussion about that a short while ago.

[rcv]

Got it, thanks guys.  I actually have an extra block plug, and it fits perfectly. I’ll order a 3/4” to 1/2” barbed reducer and that should get me set. Very happy to avoid any under-the-dash work as that’s a whole mess I’d rather avoid. 

[siteunseen]

I hope you have better luck than I did getting that elbow out of the head. Mine wouldn't budge! Damn near warped the head before I gave up. I didn't use heat though because of the rubber valve seals nearby.

[rcv]

Fortunately I just rebuilt the whole motor, so it came out super easily.  My new plug is stainless, so hopefully I can get it back out again when I decide to finally out the heater back in the loop. 

[rcv]

Just a quick update: the bypass surgery was a success. I just got a 3/4" to 1/2" barbed adapter off of Amazon and replaced the Y adapter with it - everything fits great with no leaks.  I was able to run the car for a few minutes and it seemed to be cooling normally, at least in my driveway.