Block plug??

[510revisited]

Lame title. I know. In my search for places to install a temp sensor for my holley sniper setup, I came across this guy. 9/16 head. Tried to take it off but she's gonna need some persuasion. What I need to know is this.. is it oil or coolant? I'm praying coolant... 

[datzenmike]

It's coolant but if you want an accurate temperature of what's really going on in the combustion chamber, use the thermostat housing. That part of the block will be the coolest. The head is always hotter. There's a thermal vacuum valve that is usually broken or it's disconnected, as most delete their EGR anyway. I took the valve out and put a plug in the hole just for looks.

 

 

 

 

[510revisited]

35 minutes ago, datzenmike said:

It's coolant but if you want an accurate temperature of what's really going on in the combustion chamber, use the thermostat housing. That part of the block will be the coolest. The head is always hotter. There's a thermal vacuum valve that is usually broken or it's disconnected, as most delete their EGR anyway. I took the valve out and put a plug in the hole just for looks.

 

 

 

 

I was thinking of tapping an extra heater tee where the heater core hoses come off the head. But the instructions state a place with lots of flow. Unless I'm wrong, I dont see that being a high flow area. 

[Stoffregen Motorsports]

I think there's probably sufficient flow at the t-stat housing.

[datzenmike]

You would need to have the heater turned to HOT for that to work. In the off or cold position the heater valve is closed.

[510revisited]

3 hours ago, datzenmike said:

You would need to have the heater turned to HOT for that to work. In the off or cold position the heater valve is closed.

That's what I thought. So with my only options being the intake manifold, thermostat housing, heater tee, or the plug this thread is about I'm at a loss. I will contact holley in the coming days and speak to them about the thermostat housing. I thought, for a hot second of removing the stock temp sending unit and going with that hole. Is there any place on the head that could be drilled and tapped for the sensor? If need be I can get creative. Even thought about welding on a fitting to the underside of the intake. Where the coolant actually flows. But then I gotta worry about cooking the sensor and wires. 

[thisismatt]

Pretty sure where mike suggested *is* where you want to put it.  That's the side where the coolant will be warming up.  Holley doesn't want you to put it on the cold side of the thermostat.

[distributorguy]

Put it in the thermostat housing where ALL the coolant constantly flows, and its the hottest you'll see anywhere int he engine.  That's where we run ours with EFI.

The heater hose is extremely problematic - worst possible place.  

The intake manifold is what you do on V8s where coolant flows through the intake where the T-stat is located.  

Remove the vacuum switch  that you're not using and install the sensor, right adjacent to your other coolant temp sensor for the dash gauge.  Or did the factory put it in the wrong place??? 

🤭

 

 

[datzenmike]

On 9/15/2019 at 8:13 PM, 510revisited said:

9/16 head. Tried to take it off but she's gonna need some persuasion.

There are small 10mm head bolts around the front of the timing chain area that have to come off as well as the 10 head bolts. If you've never taked a head off before make sure you block the timing chain tensioner from falliung out.

 

 

Z car thermostat housings can have the water temperature sender hole and up to 3 more for various senders also.  This one is upside down.

[510revisited]

So are the t-housings interchangeable from l20 to l28

[datzenmike]

Yes. In '79 they all changed to three bolt top cover over the thermostat so if all you can find is the three bolt get the cover with it.

 

[510revisited]

Damn, and I just put a new new one on a few months back. I'll look into the idea. Right now I'm trying to work out a way to make the connection from intake to thermostat to lower radiator hose with hose and AN fittings. Debating, if room permits, on putting a fitting in between intake and thermostat in the hose for the sensor. 

[datzenmike]

Well the water from the intake will be slightly air cooled from passage through the intake. I think the thermostat housing is the best. You could drill and tap the one you have.

[bilzbobaggins]

What about in the bypass hose?  Just to play devils advocate. 

[datzenmike]

I guess it would work but again it is a mix of hotter and cooler water from the intake and structurally, just out there hanging. In the thermostat housing would seem better, visually too.

[510revisited]

So I found a thermostat housing off of a 79 zx. The lid and all. It should be delivered today. Hopefully its in good shape. I will mock it up and report back. From the images it may work better. I still have yet to contact holley. 

[Stoffregen Motorsports]

I predict Holley telling you that the location in the t-stat housing is ideal.

[510revisited]

2 hours ago, Stoffregen Motorsports said:

I predict Holley telling you that the location in the t-stat housing is ideal.

I'm hoping your correct sir... just for clarification, the coolant comes out of the head, into the housing, through the t-stat into the upper half of the radiator, only to cool and then recycle from the bottom up..? I should know this.

  I recieved the new t housing. A little rough but I think it may work. I was able to remove 2 of the 3 sensors on the housing. One is busted up pretty bad so I'll probably drill it out. I'm curious if anyone knows the thread sizes on the holes. Bpt like all the others? Npt? It doesn't really matter, but I'm still curious. Im gonna add an "an" fitting to run coolant from the lower radiator hose. The biggest hole is just a wee bit too small for the holley temp sensor. I may just drill and tap it accordingly. Nice thing is that the other holes allow me to run my bypass in a better fashion. Thanks again datzenmike for the suggestion. Your knowledge is amazing. 

[510revisited]

On 9/21/2019 at 7:12 PM, Stoffregen Motorsports said:

I predict Holley telling you that the location in the t-stat housing is ideal.

Nope. They insist the intake. I have a buddy who has a buddy who tigs. I'm gonna just pull the pin and weld an npt bung onto the manifold. I have one smog intake, and two non smog intakes. One of them should work.

[Stoffregen Motorsports]

Do they know this is not a small block Chevy?

[datzenmike]

Is the sender for water or air temperature????

 

If water, you want the thermostat housing. The intake is warm enough to hold it's not the true temperature of the engine or the coolant..

[thisismatt]

Seriously.  Unless you have a coolant passage through the intake that you're tapping into, then that is the wrong place to put a coolant temp sensor.

[datzenmike]

This!

 

The coolant in the runners is giving up heat to warm them. The closest to true engine temp is the thermostat, where Nissan put the temperature gauge sender.

[Stoffregen Motorsports]

Trial and error might be the best method here. It would be easiest to try the t-stat housing first, because you don't have to weld anything.

 

I still say the t-stat housing is the best area for a coolant temp sensor. I have doubts that the people at Holley really understand the Nissan L series.

[510revisited]

Well let me say first, thanks for all the input. I'm not saying you guys dont know your shit. Obviously you must, which is why I'm here in the first place. 

7 hours ago, Stoffregen Motorsports said:

Trial and error might be the best method here. It would be easiest to try the t-stat housing first, because you don't have to weld anything.

 

I still say the t-stat housing is the best area for a coolant temp sensor. I have doubts that the people at Holley really understand the Nissan L series.

When I emailed holley, I specified what the motor was. Hoping the dude would maybe look it up and say differently BECAUSE this isn't a small block. I know this is a first, and I'm a Guinea pig. Maybe there's a reason I'm the only one... 🤣. However, I like stoffregen's idea. I will put the coolant sensor in the thermostat housing I bought on Mike's suggestion. If it doesn't work, I'll weld a bung to one of my 3 intakes and give it a shot. Worst scenario, I blow it all up! He did say I could run it in between the intake and t housing, but that's a separate set of problems. 

     In hindsight, I will try the line too before welding..

Edited September 25, 2019 by 510revisited