Temp sensor for AFR heads

[atm70chevy]

Can someone please tell me what size temp sensor goes in AFR heads? I bought an AC Delco sender with 3/8 threads and it was too big...

Thanks for the help.

[AussieinNC]

Does the end of the sensor bulb fit into the hole in the head?

Do a search on this board for "coolant sensor modification".....one of the members here does the modification...he turns down the standard one and then recuts the correct thread size....

BTW...AFR will drill and size the coolant hole in the head if you tell them when you order the heads...

This entire scenario has been around for a while now...am left wondering why aftermarket folk are still asleep at the wheel...

[atm70chevy]

Yes the end of the sensor will fit in the hole. The threaded part is too big for the hole in the head. I called AFR twice and was told both times the sensor opening was 3/8....

[Coley]

It looks like you need to investigate and determine exactly what you have.
They say the hole is a 3/8" threaded...and your part with a 3/8" threaded end doesn't fit. Can you find another 3/8" (Npt-pipe) part and try it to make sure that it isn't the AC delco part you have?
That said, you need to first determine that the hole is threaded...it might have missed the 'tapping' operation when it was getting made so it may be just the pilot hole. Use a small mirror or your fingers to determine that there is indeed a tapped/thread form in there.
If it is tapped you need to try a few different threads in there to determine exactly what they tapped in there....if they tapped it.
Can you feel a thread form in the head?

Coley

[AussieinNC]

Originally Posted by atm70chevy

Yes the end of the sensor will fit in the hole. The threaded part is too big for the hole in the head. I called AFR twice and was told both times the sensor opening was 3/8....

3/8 Gas or NPT drill size is 9/16", I suspect the AFR tech cut the hole to 3/8 UNC...

Looks like you have a couple of choices,,,

have a shop drill and tap the hole to suit your sender or

source an adapter to convert from the small thread to the 3/8 gas thread of the sensor or

turn down the sensor body and re-thread the sensor to suit

[A1971Blazer]

There's a big difference in 3/8" SAE thread and 3/8" NPT....you need to be sure that it's 3/8 NPT...I can modify a sender for you..I may have one on hand that is already done..
http://67-72chevytrucks.com/vboard/s...r+modification

[AussieinNC]

There you are ! If you read my first response, I mentioned a member who did the modification...

I am not sure what the actual size of the threaded hole is,,,ATM70Chevy should be able to advise...

Thanks for jumping in...

[AussieinNC]

There is another possible solution...put the sender unit in the manifold water port branch at the front of the engine.

Debate is open on whether the manifold location runs cooler than the head providing a possible inaccurate reading.

Manifold locations are usually close to or tapped to 3/8 NPT.

[atm70chevy]

Thanks for everyone's responses. The problem was I'm an idiot.... The hole in the head is 3/8 and the temp sensor that I had and thought was 3/8 was actually 1/2.... I was having one of "those" moments! Haha