The Stovebolt Site Forums The Shop Area Engine Shop Water temperature sender head port

Hi,
On an original temperature sender for a 1950 truck what size is the port drilled into the head? 3/8"?

I have an 848 head on a 261 (1962 head and engine) with an enlarged hole for an electric sender. The 62 hole is 1/2". However, I used a bushing to get it from 1/2" down to 3/8" in an attempt to use the original gauge sender and the old '50 sender is still flopping around in the 3/8" hole.

Anybody else have this issue?

The early temp sensor hole is not a pipe thread- - - -I believe it's the same as a 5/8" coarse thread bolt- - - - - -5/8-11, maybe? The threaded bushing that's built onto a mechanical temp gauge capllary tube threads into an early head without adapters. Aftermarket direct reading gauges have one of those fittings included in the hardware kit that comes with them.
Jerry

I just figured out my 216 is 5/16. Not sure about 261 heads

This adapter/reducer has worked on my later 235s/261s.

I posted a message incorrectly - Martin noted this below - I moved the message to the correct thread. Sorry

Fox, Is your 261 a Canadian engine as mine is? I also have a very big threaded hole in mine, not sure the size but it has a reducer for the sending unit.

Tim,
Yes that's what it is. However I just went down to the hardware and got a pipe bushing. 1/2 to 3/8 and it was sloppy. As Jerry said, it must be a regular thread. Perhaps I'll grab a 1/2 to 1/4, drill it out and then tap it to fit if I can't find a proper one locally.

Panel, yes it's Canadian with the big port. I'm not sure of port size on earlier Canadian head for a 261.

"Danger, Will Robinson!"- - - - - -If you drill and tap, you're going to be making a big mistake and probably ruining the head. The 5/8-11 adapter has a flat bottomed area for the sensor bulb to seat against, and the straight thread above it. Unless you have a way to machine an adapter with that shape, there won't be any flange for the bulb to tighten against. An aftermarket mechanical gauge with a sensor bulb costs just a few bucks, especially if you get a cheap one on Ebay, and it will have all the adapter hardware you need. Even if you don't use the gauge, you'll be able to install the one you're working with.
Jerry

Oh no Jerry, I agree with you. I won't be drilling the head. I will be making my own bushing. I will be drilling and tapping into a bushing to get the old bulb sensor to fit. Then install that into the head.

The threads on an original 1950 mechanical senson is 5/8-18

If your head is 1/2 pipe you can use the adapter tim linked to above

Napa auto carries the apapter also

...example...

Yep- - - -5/8" fine thread- - - -not coarse!
Jerry

Probably the only place you will ever find fine threads used, in cast iron, on a Stovebolt.

It was pretty common on Brit sports cars back in the 1950's. Triumph, MG, Jag, etc.
Jerry

I noticed the "shoulder" inside an older spare head I had in the shed. If I go this way, I will have to stop short with the pilot hole and then use a bottom hole tap to do this.

Or do the simple, easy thing and get the right bushing! Haha! Thanks for the links guys. I'll be doing this.

Thanks for the measurement too, fellas. I noticed that when I was in the shop.

Jerry raised a very important issue..... Unless you have a way to machine an adapter with that shape, there won't be any flange for the bulb to tighten against.

The original early 216 engine the sender has that special flange that no regular adapter will allow you to seal the sending bulb. The early flanged senders are easily recognized by the four sided bolt top...... our solution when working on the 261 is to buy the cheap aftermarket temp. gauge JUST to get one of the adapters in the kit .

Caution: if you over tighten the adapter into the head.... the head can crack........ so far the JB Weld on the thread is holding and has been for a few years.

We have a further complication...... the early military 216 trucks had a steam line connected in that hole and vented just under the radiator cap. It was meant to release air pockets that may have formed inside the 216 heads during very steep descent or climbing. I means having a T fitting with a line to the radiator and the heat sender bulb fitted to the top of the brass t fitting. We first tested them in operation using a clear nylon line and where amazed at the froth that was sent to the radiator....after some time in level position it becomes clear green antifreeze. At that point, the temp line was replaced by a solid steel brake line to the rad.


Bob C
Can't remember how to attach a picture!!!!

Hi Mr. Johnson
I noticed this discussion and as I have three 261 engines and was about to order some small stuff I ordered two bushings.
So if you are in need in the spring I will send you one. The photo from Classic Parts makes them look like made from stainless.

Remember, Stay warm.
Howie

"Mr. Johnson?

The photo from Classic Parts makes them look like made from stainless."

The Classic Parts bushing that I referred to above is brass/copper.

However, I dimly recall that there might be some vendors selling a SS fitting?

Fox,
if you want to buy one in Canada I think Bill's Truck Shop here in Ontario would carry them. They generally are pretty good at sending them out pretty quickly.