Temp Sender ?

I want to first and formost thank everyone who took the time to respond to this topic. If anyone was bored with just another over heating thread well I guess I dont have anything to say to that, but maybe you were reading in a bad spot for a person that is bored with overheating subjects.

This problem speaking just for myself mind you, has been an eye opener for me. I have been building Hot Rods for a few years now. Way to keep myself busy after I retired. I learned that building a Hot Rod and Fixing a Hot Rod or maybe more correctly being a "mechanic" are two complettly and different things. I learned to be a Mechanic first and formost you must be able to diagnose a problem before you can fix it. I mean I can twist wrenches, remove and replace things, but that is a very small part of the Mechanics job. I also learned that I personally have the Diagnostic talent of the average Tree Squirrel. I mean I am a retired Marine, Marines don't have to be smart, just willing, I fulfill that role complettly.

When I started this overheating thing I had a couple of goals. One was to stop the overheating, and two to understand "THE" why of the overheating problem. I was a little ambitious and over estimated my learning curve a lttle with the why-- Refer to the Willing and dumb thing---

I bought temp gauges ( in the end 5 of them ) went through half a dozen gallons of antifreeze. Made 12 and a half mess's in the shop and made my shop guy clean them up. Busted all the skin down to the bone on 5 knuckles removing that stupid stuck plug from the Intake Manifold. And par-Boiled all of the skin on one arm because I was too dumb to wait another 30 min before I pulled that sender out of the head from underneath were all of that Hot Water had no where to go but right down on top of me.

I went to all of that trouble and loved every min of it. I mean I switched temp senders into every hole on that 383 that I could find. Found that are are some serious difference's in temp from one place to the next. Another words water temp doesn't always mean "JUST" water temp. I also tested the accuracy of the gauges thereself. Just how accurate are they? And just how accurate do they really need to be? The later of those questions are up to those smarter than me-- That would include just about every living soul that reads this.

I mean I really did want to know the answer of why? I took the temp gauge senders and put them into boiling water with a thermometer just to see. I found out that the Autometer "MANUAL" gauge is pretty accurate within 4 or 5º, and very sensitive and I mean VERY. It changes temp almost instantly, I even heated the gauge senders up to 200º in the boiling water and then dumped a hand full of ICE into the water. The gauges all read the cooling effect just as fast as I dropped the ice in. I also found that the Autometer "ELECTRIC" gauge are accurate to within pretty close to the 4 or 5º, but they are much slower in there reaction to different temp changes. As a matter of fact they reacted slow enough to dump the ice and then reheat the water and register a very small needle movement if any at all.

So here are my conclusions. The temp sender in the head is not just reading the water temp, it is reading that along with the rapid heat transfer from the 1 and 3 Cylinders or the 6 and 8 cylinders depending on which head it is in. Taking temp readings from the Intake Manifold is in a lot of ways More Comforting, there ARE NOT the rapid swings in temp, it stays pretty constant in that location. And I think if you are using a "Manual" gauge that is a pretty good spot.

I believe that the head mounted sender is probably a place were you recieve a more accurate indication of what is going on inside the motor, it also is a lot more un-nerving there, and probably if you use the head location I personally would use the Electric gauge as it doesn't read as fast thus the Un-Nerving thing.

After going thru this and my over heating problem I think I do need a shroud, as I think that will help a lot. My engine is a pretty highly modified 383 and may just run a little hotter than some. The way it is set up now it has the manual Chevy Fan bolted to the water pump, and it also has a spal single pusher fan on the outside of the rad. I believe that the electric fan in this configuration is a obstruction and also part of my problem. Well that and the fact I found a 2 inch split in the heater hose, Whoops I probably shouldn't have mentioned that!!

Roland