Well the Autometer gauges came today, and the mechanical water temp gauge's sending unit if freakin huge. The smaller of the two fittings it goes into is 3/8"!

I originally wanted to put it in the stock sending unit's location, but looking at the cylinder head, I don't think there's enough room to drill and tap the hole to 3/8". I suppose I could use the coolant draincock on the block and drill+tap that, but I'd REALLY like to retain the stock location if at all possible. Is there any way at all to do this, or am I stuck drilling & tapping into the block?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

You can get 3/8" to 1/8" adapter fittings (1/8" NPT is the stock thread for the temp sensor I believe... or at least one of them. I thought I heard that the sensors came in 2 different sizes).

Since when did they put draincocks on blocks? I haven't seen that. Can you take a picture?

I take it you still can't find the water passage plug I was talking about earlier. Can anyone shed some insight as to which blocks had the 3/8" plug that lead to the water passageway on the passenger side, near the oil temp sending unit?

Actually that was the "draincock" I was referring to. I guess drain plug is a more accrate term for it. It didn't look like 3/8" when I eyeballed it, but I'll take a closer look on Monday and see if it's the right size. The sending unit for the new gauge is about 2" long and 1/4" diameter, so using an adapter for putting it into the cylinder head is out of the question

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

2" long isn't that bad. After the height of the connecter, the GM temp sensor I used, along with the brass fittings required to convert it to 1/8", it was about 4" high.

Maybe you need to change to a newer cylinder head.
mid/late 70s heads throug the 80's heads have all various combinations of extra holes drilled in the front near the thermostat so there was a place to fit all the vacuum switches and comptuer temperature sensor. Some of them have 2 or 3 large NTP holes in addition to the small temp gauge sender hole.
Maybe one of those later heads will give you ideas where to drill a new hole in yours.

I'd definately jump on one if I could get it (and had the cash handy). How much would I expect to spend on just a head without any valvetrain components?

And would I be able to kep using mechanical valvetrain parts with it?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

this is what I've been bitching about for years! I am told, they once sold a smaller bulbed capillary for 'special' applications, but have discontinued selling them. Once again Mopar owners are left sucking the hind one.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

So did you put in an electronic one or did you put the bulb in that spot on the block?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

I've done nothing, but complain! I'll probably drill and tap in the vicinity of the thermostat housing.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

I am not shy about using a drill and a tap but I tend to do my "handywork" on the easest parts to change...
What I have been doing is finding the cast iron thermo covers and drilling / tapping a hole into that, just off-set the fitting a little so the bulb misses the top of the thermostat.
I have also put (moved) the factory sender into the waterpump inlet neck, with this I can see water exit temp. and water inlet temp. (before and after the radiator temp)
DD
http://www.dutra.org/pictures/engine/pa ... itting.jpg
http://www.dutra.org/pictures/engine/pa ... r-head.jpg

Hey good idea putting it in the thermostat housing. That'd be easy to do, too. Now here's a silly question, but what thread count would a 3/8" NPT tap have? I keep trying to find one, but no 3/8" taps that are labeled NPT.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

3/8-18 NPT. That is NOT the same as a bolt thread. Pipe taps are tapered. Do NOT run it all the way in or your threads will be too large diameter. The deeper you run the tap, the bigger your threads will be.

Technically, I think that not all pipe thread is tapered. But you are 100% correct here, in this particular instance, Craig.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

Yes, I've seen some straight pipe thread taps around. Not sure where those get used. Pipe thread depends on the taper to produce an interference fit.

Straight pipe thread? What does that look like? I thought all pipe thread had a taper, thats what makes pipe thread pipe thread in the first place (try that 10 times fast!).