[Hombre0321]

I asked this question on another Forum and got some interesting comments, wonder what some of you guys might have to say or maybe some thoughts on this subject.

What is the correct location for the Temp Sender on a SBC? Car is a 1957 Chevy running a 383 and a Muncie 4 speed. This is a new aquire for me and playing around with it I found that the Temp Gauge didn't work. I pulled the gauge and found that the sender was cut or broken. It "WAS" a cheap gauge and it also was manual using capillary tubing. This gauge was located in the drivers side head, in that spot on 350 heads were there is a plug between the # 1 and #3 plugs. I used this same spot as I could not remove the plug from the intake manifold. I installed a manual Autometer gauge.

Got it buttoned back up replaced the coolant, and went for a little drive. Temps after 20 min or so were a little high to say the least. After warm up the temp got up to 220º and then over the next 5 or 10 miles went as high as 230º. I came to a big hill with a down grade of a mile or so, shifted into nuetral and coasted down that hill at 60 MPH. Thinking here was engine would be at an idle and air flow would still be 60 MPH. That worked and it cooled down to 195º to 200º pretty quick. As soon as I hit level ground back up went the temps to 230º.

For me this is just to hot, engine runs fine and just doesn't seem to be hot at all, does not puke out the over flow tube, doesn't diesel like a hot engine will some times, it does really seem fine. But it is just to hot for me and something is not right. As I pondered this problem I got to thinking about that spot in between those two plugs. Is that a good place for the sender? I believe I have seen Chevy use that same location, or at least I think I have seen Temp Senders in that spot. Is that position between those two plugs and in the head a good indicator of ---Water Temp---?

Thoughts, Roland

 

[cffisher]

That is where it belongs . You could put it in the intake. Probably runing hot because of engine work ?? could be thermostate, to small a rad timing. If it is not over heating I'd try another location. there are a lot of reasons for runing hot. Before I'd get real excited I'd put the sending unit in another location.

 

[Rick_L]

There are those that argue the sender in the head will report a higher temperature than one in the intake, but I pretty much don't buy into it.

If you have that sender in the driver side head, it's less than 6" from the intake manifold water passage, with nothing to add heat between them, and nothing to subtract heat either.

But you have little to lose by moving it and trying the intake manifold location, except the trouble to free that old plug.

 

[hamsman]

Roland, you might ask around and see if someone has a hand held temperature sensor, the kind you can point up close to the radiator or incoming and outgoing hoses and it will give you a digital display of what the temp is.

I have one from MicroTemp #MT100, but cannot remember where I bought it?

I would think most autoparts stores would have one or most auto repair shops?

This would a leasat give you some idea of the temps vs the temp guage.

Are you going to put in an electrical temp guages? I did, works great.

Don, aka.....the hamsman

 

[hddude]

just wandering what you are using for cooling? radiator, degree of thermostat, water pump, how far away from the radiator is the fan located?

 

[chevman57]

I can`t see were the sender in the head would hurt it. GM put them there for years on the V-8. I like the digital temp idea.
Terry

 

[Hombre0321]

OK Guys Thanks for the response. Here is some of the things I have tried and some of the things I have been told.

I was concerned with those temps, got to thinking about the head location and what was around it and why it could be that hot.

So I go up to the local parts store and buy two more Manual Autometer gauges. I install one in the passenger side head that is between #6 and #8 spark plugs on that side. I wrestle that plug out of the manifold ( no easy task) and install the third one there. Rig up a gauge panel for the two additional gauges and go for a ride.

Do the 20 min warm up thing, drivers side temp is 230º, passenger side temp 235º, Intake manifold temp 190º. Well now thats 40 and 45º difference that can't be right. So I head back to the shop and remove all three senders and guages and move them around. Intake sender to the passenger side head, drivers side head to the intake, passenger side sender to the drivers side. A little note here. You just got to let these things cool off longer than I did, my haste in switching these around came with a price, I would have screamed and jumped up and down, but there is decorum and I am a retired Marine and somehow screaming would scare my neighbors especially coming from my shop.

Back for a cruise, did the 20 min thing readings were the same Intake stayed right around 190° and the other two were high just as before. One intersting thing was when I came to that big old hill and shifted into neutral the gauges reading the head temps change quite a bit. They cool down to 200º or so. The gauge reading the temp from the Intake Manifold never varied much if any at all, and that hill had no effect what so ever on the Intake Manifold temp.

I guess I'm just not smart enough to figure out what all of this means. I suppose it means that different spots are different temps---DUH !! I have been told and can only take them at there word that in the more modern EFI engines the Temp is taken from the Intake Manifold on Chevys, and the reason is it is a more constant temp and its location right next to the Thermostat and the upper rad hose is where the "Water Temp" is the hottest on its way to the rad for cooling. I can for pretty sure say it is more constant in my simple little experiment, and lower too.

I am pretty sure that the head location is a place I have seen temp senders before on stock or un modified cars. But if that is true it was then connected to some sort of Factory gauge and while sometimes they appear to be a anolog type gauge in reality they certainly are not. Temps as high as I saw 235º from the head would alarm most folks "I Think".

Roland

 

[WagonCrazy]

I guess I'll throw my situation in here Roland, and maybe it will shed some light on what's happening with yours.

I have 3 water temp senders in my engine. The one on the intake maniford is hooked up to the stock guage in the dash. Since there are no actual numbers on that gauge, I'll just say that once fully warmed up, it reads near the H. About 3/4 of the way "over to the right" from the Cold position.

I have a mechanical aftermarket temp gauge, with sender in the passenger head between #6 and #8 cylinder. With the wagon running fully warmed up, it will sit right at 190 all day long. But, thats because...

The 3rd sender is in the drivers head, and it's the temp switch that feeds a signal to the Spal Fan Controller that is running my dual fan setup. The controller is programmable, so I've set it to come ON when that mechanical gauge (#2) reads 180 degrees. Normally, once warmed up, the wagon runs at 190 degrees, and only on the hottest of days (110 degrees) with the AC on, and in stop and go traffic for a long period, will it ever reach 210 degrees. Once I get moving....it drops back to 190.

I have a nearly stock 350 with a mild cam and a 4 speed overdrive transmission. A 600 cfm carb and that's pretty much it.

Paul

 

[Rick_L]

I think your experience is pretty radical compared to most I've seen posted but I won't argue with you.

I will say this, I don't understand it.

As far as EFI engines, the LT1 Camaro/Firebird/Caprice engines from the mid 90s have the temperature gauge sender in the head, and the sender for the pcm mounted in the water pump. But I can't comment on the difference between the two, as mine is not running yet, and I've never seen the temp output from the pcm. But I will share someday, as I do have the scan s/w.

 

[mickym521]

Roland. there is also a fourth spot you can check the temp. There is a radiator cap you can buy that shows the temp at the radiator. Draw back is you have to be setting still to check it. This is how I made sure that my dash gage was reading reasonably correct on my 383.

 

[HIGH ROLLER]

Pretty radical !! Heres radical i own a 1986 C4 vette how bout the water temp Designed by GM goes to 220 then the computor brings the fan on i have steel heads works fine, but i did redo it to come on at 180 The Aluminum heads didn't last to long. There were thousands of them built every one here gets scared when they see there temp gauge at 200

 

[Rick_L]

The LT1 factory fan start temps are about the same. With aluminum heads.

Maybe a bit high but probably no worse than the guys that want to run their engines dead cold at 160 degrees.

 

[HIGH ROLLER]

We run and win races not all the time, finish in the top 5 or 10 every week with 350s running 200 to 220 for hundreds of laps. I guess i am being a little misleading, we run forged pistons with little 1 inch skirts with 3 to 3.5 piston to wall, but the water temp gauge is in the intake, so its about 15 more in the head, in the heat of the moment to win or finish we have run 250 in the intake, 265 in the head, thats with a chevy head, we use Darts now, no piston to wall or piston problems with inspection, but if you keep it up you will crack a Chevy or Dart head its happened, now thats really pushing it in the hot 90 to 100 degree weather in tight racing traffic but a guy with a street car seeing 200 to 220 he should be ok but i suppose you never no.

 

[Hombre0321]

Glad to hear as much feedback as I can on this. Just came in from the shop were I moved the drivers side head sender to the water pump ( Thanks to the tip from Rick_L ) I also went and bought at the local O'Reillys a rad cap with the built in temp gauge ( that one is thanks to mickym521 ads I didn't even know there was such a crittter best $23.00 bucks I ever spent). Results were water pump sender 190º to 195º and it didn't get any hotter at all, stayed right there. Passenger side head went to 220º right away and varied some just as it has been doing. Sender in the manifold stayed at 190º, and the rad cap gauge was at 200º when I got back and shut it down.

Well after you guys comments and all of this driving and pondering I thought I had this pretty well figured out. That was until I had this thought, my 55 Chevy was setting right there in the shop next to the 57. I knew for a fact that the temp gauge in it never went over 190º. It does have a Autometer electric gauge in it, but in truth I had never thought much about were the sender in that car was. So I pop the hood and sure enough wouldn't you know it is right in the drivers side head. There is even a relief in the header flange for clearance to use the dang thing. So I guess I'm back to square one, and don't "NOW" even have a clue as to what is really going on....

Roland

 

[acardon]

"NOW" even have a clue as to what is really going on....
Roland

Are you sure you don't have air in the cooling system when doing these tests, by moving the senders and testing imediately after? A friends ramjet had problems with the ECM temp sender for 3 months until he finally blead the air out of the system.

 

[hddude]

i just bought one of those caps with the gauge in it. my water temp gauge in in the manifold, and the gauges read 20 degrees difference.

 

[Str8axle]

What lb. rad cap are you running? Stock cap is 7lbs i believe. Higher pressure will raise the boiling point and in essence, you'll run warmer.

 

[hddude]

if you`re asking me, 7.

 

[Rick_L]

"Higher pressure will raise the boiling point and in essence, you'll run warmer."

First part is true, second isn't.

If you ever start boiling, it's a runaway situation because steam isn't as good at heat transfer as liquid water, plus you're losing coolant to the overflow or to the ground. So you have to stop putting the heat into the coolant. I.e., shut the engine off.

If you raise the pressure, you CAN run warmer without boiling, but raising the pressure doesn't make the temperature go up.

 

[Petmils 1957 4DR Belair]

Wow another over heating post . This subject is the most confusing I see on this site. It's all so interesting and everyone problems are different. Mine is the standard one it over heats in hot weather while idling I'm going to get a shroud hopefully soon to alleviate the problem I hope.

I wonder what people did in the 50's to stop boil overs. My Dad use to carry the old canvas water bag on the front of the rad for boil overs on his olds 88. Going over mountain passes always was a concern in those days..

Peter