Can I use the block drain for a temp sender?

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YY1

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I'd like to keep the factory gauge but install an aftermarket one that actually indicates the temp.

There is a threaded hole near the pass side oil pan rail that I believe is the block drain.

Can I use this?

It would also help hide the big, shiny spring encased sender lead in my otherwise stock engine bay.

I can't seem to find any info online about what the difference in temp might be between the water in the top of the engine and the bottom.
 
I tried it on a small block a few years ago, and couldn't get it to work. Not sure if there isn't much flow down there?
 
I have the same question. I don't see an issue with it because once the engine warm up the temperature should normalize. 65'
 
I guess the first question is, is there a well/cavity there. Temp senders do have a probe end reaching into the water. Some aftermarket temp senders are too long for the correct intake location.
Of course the water would be hotter there, like oral thermometer versus rectal thermometer. OEM temp sender reports a general/average water temp. The water jackets around cylinders would read significantly hotter.
 
Block drain at bottom = not a good location to get an accurate temp reading, select somewhere up near the t-stat.
 
like oral thermometer versus rectal thermometer.
probe end reaching

easy:poke:
 
Most of the block drains are full of casting sand. Not a real good place for a sender.
 
This is kinda related. I install radiator petcock fittings in both of those locations. (One on each side of the block). Then when ever you are pulling the intake or the heads, you won't have water/antifreeze running every where like the intake valley or cylinders. If you open these drains before you start taking your engine apart. Much cleaner, less messy.
 
This is kinda related. I install radiator petcock fittings in both of those locations. (One on each side of the block). Then when ever you are pulling the intake or the heads, you won't have water/antifreeze running every where like the intake valley or cylinders. If you open these drains before you start taking your engine apart. Much cleaner, less messy.

I also do that on all engines.
makes prepping race engines for winter easier,
then in the spring, drain the antifreeze
 
I have installed a pipe T for this in the past. Original sender at top & the thermal sender in the side port.

This also works if wanting to keep your original oil sender gauge & want to add a gauge showing the actual PSI.
 
This is kinda related. I install radiator petcock fittings in both of those locations. (One on each side of the block). Then when ever you are pulling the intake or the heads, you won't have water/antifreeze running every where like the intake valley or cylinders. If you open these drains before you start taking your engine apart. Much cleaner, less messy.
All of the old Oliver farm tractors are set up this way because they didnt have anti-freeze back then and used alcohol in the winter.
 
If your sender is small, like 1/8--1/4" pipe, I've thought about drilling and tapping one of the rear intake manifold "blanks" where they cover the water ports in the rear end of the heads.

doubt you want to do that for a mechanical gauge, although "I guess" you can buy 3/8" pipe adapters for them
 
.........................

Q... What's the difference between an oral and an anal thermometer ?

A... Taste

A nurse reaches into her pocket and pulls out a rectal themometer and says, "Some @sshole has my pen".... :BangHead:
 
The block drain is at the bottom of a V-cavity, so it isn't very deep there, just enough clearance for the plug. When you remove it, coolant usually doesn't flow out until you break up the rust crud w/ a screwdriver. A stagnant area which won't measure typical coolant temperature. For sure don't screw one in, bottom out, and strip the threads or crack the block. The plug is 1/8" NPT in a V-8 (one on each side) and 3/8" NPT in a slant (single).
 
The block drain is at the bottom of a V-cavity, so it isn't very deep there, just enough clearance for the plug. When you remove it, coolant usually doesn't flow out until you break up the rust crud w/ a screwdriver. A stagnant area which won't measure typical coolant temperature. For sure don't screw one in, bottom out, and strip the threads or crack the block. The plug is 1/8" NPT in a V-8 (one on each side) and 3/8" NPT in a slant (single).
V8,1/4” npt. Just had mine out.
 
V8,1/4” npt. Just had mine out.
Correct, sorry for the mis-info. In all my cars, I installed a knock sensor in the drain holes, from a 85-95 Chevy V-8 (as GM did). Fits directly in the SB & BB drain, needed a 1/4 to 3/8 NPT bushing for my slant. The GM knock module can send a "I'm knocking" signal to an engine controller (ex. Holley Commander 950), which retards the spark.
 
Correct, sorry for the mis-info. In all my cars, I installed a knock sensor in the drain holes, from a 85-95 Chevy V-8 (as GM did). Fits directly in the SB & BB drain, needed a 1/4 to 3/8 NPT bushing for my slant. The GM knock module can send a "I'm knocking" signal to an engine controller (ex. Holley Commander 950), which retards the spark.

Interesting. Is there a thread on this? can the sensors function stand alone like just a warning light?
 
Interesting. Is there a thread on this? can the sensors function stand alone like just a warning light?
I would think so. The GM knock sensor is just 1-wire (blue) which runs up to the knock module on a bracket on the intake manifold. Sig- is ground. You can find wiring diagram for the module (try Megasquirt site). As I recall, it outputs an on/off 5 V signal that is high when sensing knock. I plan to use w/ a Holley Commander 950, but no reason you couldn't just light a dash LED. The sensor is just a piezo-electric quartz crystal (like a "crystal" microphone), presumably with a weight tuned to resonate when the engine is knocking. Some have to tried to figure out the various GM PN's and worry if a six cyl or even Mopar/Ford V-8 would sense the same. I recall the conclusion is that GM used the same PN for V-6 and V-8 and they just varied by year or whatever, so "should work". They are all push-rod engines, so should sound similar. Holley's algorithm just keeps increasing the spark (within limits) until it senses knock, immediately jumps back ~2 deg, then starts creeping up again. I expect most factory engine controllers did similar, so it is always finding the sweet spot for any cheap gas you put in your ride. SAE papers I read in the early 1980's (when developing such) said a little knock actually improved combustion (efficiency and power). By the time the driver hears pinging, it isn't "minor". Thus, I expect they are designed to always allow knock just below a threshold.

While picking GM, grab the 8-pin HEI module inside the "small cap" distributor, the pickup cable (snip), unplug the cable to the coil, grab the coil and power/tach cable (snip). You can connect the module to a Mopar e-distributor pickup (2 ways, only 1 sparks best). TrailBeast here kits those parts (HEI, not knock) if willing to pay a lot more to avoid a junkyard.
 
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