CTS (coolant temperature sensor) for Holley EFI on 240

[Baxsie]

I am trying to get the Holley EFI single-barrel (Autolite 1100) going on my old errand pickup.

The first issue is that I am having trouble getting a good place for the coolant temperature sensor.

The factory location is too small for the sensor supplied by Holley, so it would require some kind of adapter -- but this would pull the active part of the sensor out of the flow, plus I'd lose the factory gauge.

I have seen the Dorman part and the Ford part to tee it off the heater hose. This would work fine in the winter - when the heater has coolant flowing through it, but I do not see how it could work in the summer when the heater valve is shut and there is no flow.

I have seen thermostat spacers for the V-8 engines, but I have not seen one for the SIX.

So my questions:

1) Is there an easy good solution I have missed?​

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2) Is there a mechanically smaller sensor that is electrically compatible that would fit in the factory location?​

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3) Is there a thermostat spacer that will work on the SIX?​

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4) Is there a safe location on the head that I could drill and tap that would put the sensor into the coolant flow?​

I would be grateful for any advice, ideas, or knowledge. Thanks.

 

[guhfluh]

Look at mid 80-90s thermostat housings. They have a sensor provision.

 

[pmuller9]

Look at mid 80-90s thermostat housings. They have a sensor provision.

85 to 90 housing

 

[Baxsie]

Thank you for your replies.

It seems to me that a closed thermostat would not allow that position to see the warm water from the head during warm-up.

As I understand it, the EFI temp sensor information is most critical during warm-up, is that right?

Or is that housing used with one of the thermostats that have a small hole to allow a small amount of fluid to pass during warm-up when the thermostat is closed?

For reference, here is the factory temp sensor for my 1969 Ford F100 240 inline six:




On that same side of the block, lower and to the front, there is a threaded plug and a freeze plug:



Could that threaded plug be used for a temp sensor (still not sure if the huge Holley sensor would fit )? I assume that the head warms up more quickly than the block?

 

[pmuller9]

It should work if there are small holes in the thermostat.

Show a picture of the Holley Sensor.

 

[Baxsie]

Supposedly it is identical to this:

https://www.oreillyauto.com/detail/c/standard-ignition/standard-ignition-2-terminal-sensor/std0/tx3?q=tx3+coolant+sensor&pos=0

Holley provides the highly respected "Made in China" brand sensor:

 

[bubba22349]

Looks like the right size US NIP thread to fit in either on of those block's threaded bosses. you could also use a brass T fitting to mount it in the near the head deck and also have your stock temp sensor too. best of luck

 

[Frank]

Supposedly it is identical to this:

https://www.oreillyauto.com/detail/c/standard-ignition/standard-ignition-2-terminal-sensor/std0/tx3?q=tx3+coolant+sensor&pos=0

Holley provides the highly respected "Made in China" brand sensor:

View attachment 10898

Baxsie- welcome! This housing has the provision guhfluth was referring to in post #2. Your sensor will fit the sensor port. It's for the factory ECM engine temperature sensor. You will have to modify your heater hoses to allow flow year round, but worth the effort to have the accuracy of electronic EFI. Don't know every year, but I know 1990 and 1993 have it. The one in the pic is off a '93 300.

 

[hodaka100]

Factory 85 e250 heater hose bypass.
A Chevy express van has a one piece plastic bypass.

 

[Baxsie]

@hodaka100 Does that heater bypass part have some kind of a spring and valve in it? Otherwise it seems like your heater would never really have great efficiency in the winter since it would be easier for the fluid to turn around and go back rather than force itself through the heater core.

Right now I am leaning towards putting up the EFI sensor at the factory location and moving the factory gauge sender to that threaded port on the block.

I was talking to an older fellow at Napa and he said he thought he remembered the 240 and 300 having threaded port on the rearward facing the surface of the head. Basically, the sensor would come out between the head and the firewall.

I'll have to get my head back there and see if I can determine if that's true or not. Otherwise I think I will go with the EFI sensor in the factory location and move the factory sender to that threaded plug on the right side of the engine.

 

[Frank]

@hodaka100 Does that heater bypass part have some kind of a spring and valve in it? Otherwise it seems like your heater would never really have great efficiency in the winter since it would be easier for the fluid to turn around and go back rather than force itself through the heater core.

Right now I am leaning towards putting up the EFI sensor at the factory location and moving the factory gauge sender to that threaded port on the block.

I was talking to an older fellow at Napa and he said he thought he remembered the 240 and 300 having threaded port on the rearward facing the surface of the head. Basically, the sensor would come out between the head and the firewall.

I'll have to get my head back there and see if I can determine if that's true or not. Otherwise I think I will go with the EFI sensor in the factory location and move the factory sender to that threaded plug on the right side of the engine.

Unless my mind is totally out to lunch, the only orifice on the back of the head is a freeze plug. Yours is a 240, not familiar with that one, so may have a threaded plug.
Also, I'm not pushing the housing in my pic on you, but it is the most accurate location - no, it is the ONLY accurate location -for pre-open thermostat engine temp. You are right that the Sniper system needs accurate cold engine data. The Ford engineers used the spot on the heater hose outlet for that same reason with the introduction of EFI. The coolant flow in the bypass is strong with the t'stat closed, and the temperature of it is the net sum of the whole engine as it warms up. There's very little circulation thru the engine when the t'stat is closed (none, if you close a valve to the heater core). Hot /cold pockets are all over the engine. There is no spot on the block or head where an accurate average temp of a warming-up engine can be found. The only place to assure 100% cold engine mixture control accuracy for the ECM is in the bypass line coming off the t'stat housing.

 

[Frank]

The heater hose set up is not too difficult to effect. I'm not currently using this set up, but have on several old vehicles like yours where the heat-off was controlled by the coolant flow. I did it to keep circulation while the engine was warming up. If the heater hose system is shut off, the coolant in the block/head is totally stagnant until the t'stat opens. Not ideal! FWIW, industrial diesels have a t'stat system that allows full flow of the coolant when warming up, to prevent hot pockets and uneven heat distribution before the t'stat opens.
2 hardware store ball valves, 2 Tee's, some hose clamps- you're in business.
An artist I am not, but you'll get the idea. lol

 

[Baxsie]

Thanks for your reply and sketch.

If the cross-over valve had a super lightweight spring and ball valve, then it could be automatic. But that is a swirly time hole on what was supposed to be a simple project.

If I had a head that was off the vehicle, I think it would be possible to find a location that could be drilled and tapped so that the sensor would poke right into a water gallery of the head. I think that would have to be the cleanest solution.

Is there a reason the factory temp sensor location would be sub-optimal for the EFI sensor?

 

[Frank]

The current factory location would probably be effective enough for the EFI sensor. All that above was just to say that the optimal location for accurate cold engine temp is the t'stat neck bypass. the stock location would probably be fine even with an adaptor so you didn't have to drill anything out. It would not be protruding into the coolant flow, but it's close enough to get the swirling coolant as it passes by, would probably be just as effective.
I will give one plus for locating it in the rear of the block or head: no ugly wires right on top to have to route and hide. Your stock location is close to the exhaust manifold. May want to insulate the Holley EFI sender to be on the safe side, if you put it there.

 

[Baxsie]

OK, I took a look at the back of the head. Just a freeze plug as @Frank predicted.

Here is what I decided to try. Picture style.





















(to be continued . . . )

 

[Baxsie]

(. . . continued)











My hope is that the sensor is close enough to the swirling hot water in the head to give an accurate reading with or without the heater on.