What temperature sensor do I use in new style head?

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cudajim

cudajim

cudajim
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I installed a newer style 225 slant head (1975 vintage) on my old block (1967 or so) and everything worked out just fine except for the temperature sensor. The sensor hole is bigger on the newer head so I used an adapter but only the end of the sensor pokes into the water and now it barely works. I need the proper setup, whatever that may be. Can anybody out there help?
 
I have the same issue, I have 2 ideas. Instead of the sensor I'm going to put a tee in the adapter, and on one side of the tee put in the original sending unit and on the other side, the bulb for an aftermarket style temp gauge.
The other idea is to find a sender with same ohm range and 3/8 pipe thread instead of the original 1/8 pipe thread.
In the old days of paper catalogs, they all had a section in back of them called a "buyer's guide". It showed specs of the part along with a rough fitment guide. And best of all PICTURES!!!! Of said part/ or at least, a line drawing or sketch.
 
Parts listings have the same part number sender listed for the years you mentioned, and all other years I bothered to look up.
cudajim said:
but only the end of the sensor pokes into the water and now it barely works.
Click to expand...
Only the end needs to be in the coolant. I assume you used a reducer bushing, but hopefully you didn't use sealant or teflon tape on it- if you did, that explains your "barely works" issue. The sending unit works by variably grounding through it's body, sealant or tape only prevents it from grounding, and you've got two layers of it with the reducer bushing. To check, attach a ground strap to the sender (alligator clip, wire) and to a solid ground. If the sender now works, then pull it out and strip off all sealer and tape, and reassemble. These pieces utilize pipe threads, and should not require sealer when correctly installed.
 
Professor Fate said:
Parts listings have the same part number sender listed for the years you mentioned, and all other years I bothered to look up.

Only the end needs to be in the coolant. I assume you used a reducer bushing, but hopefully you didn't use sealant or teflon tape on it- if you did, that explains your "barely works" issue. The sending unit works by variably grounding through it's body, sealant or tape only prevents it from grounding, and you've got two layers of it with the reducer bushing. To check, attach a ground strap to the sender (alligator clip, wire) and to a solid ground. If the sender now works, then pull it out and strip off all sealer and tape, and reassemble. These pieces utilize pipe threads, and should not require sealer when correctly installed.
Click to expand...
 
I'm just thinking here, because I don't have a slant around at this time; but-
If I recall correctly, the late slant heads had two different temp. senders and locations- one large port at the front of the head for the Lean Burn temp. sensor, and a smaller one further back along the valve cover rail for the dash cluster sender. I could be wrong, though- it's been many years and I'm gettin' old...
 
Professor Fate said:
I'm just thinking here, because I don't have a slant around at this time; but-
If I recall correctly, the late slant heads had two different temp. senders and locations- one large port at the front of the head for the Lean Burn temp. sensor, and a smaller one further back along the valve cover rail for the dash cluster sender. I could be wrong, though- it's been many years and I'm gettin' old...
Click to expand...
 
I think you're right, I stuck a bolt in that one, I should probably switch to it, I may have to lengthen the wire. In the meantime I checked the ground on the one I have, it reads 000 with the ohmmeter so it's good.
 
On my original 85 head it has 3 ports in the head, 2 are 3/8 NPT and one 1/8 NPT.
The 78 head on my newly built engine only has 1, 3/8 NPT port. But it also had an 1/8 NPT threaded hole around the corner between the valve cover and the manifold. I stuck a pipe plug in the 3/8 hole and the sending unit in the 1/8 hole
 
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