Y Block Temperature

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By Half-dude - 4 Years Ago
Hey guys

I've posted topics about this before, but I've got some more concrete information now that my car is running well enough to drive long distance. It's about the temperature the engine seems to hover at.

After about half and hour of 50ish mph driving on country roads, the temperature gauge reads just about at the far end of the solid white line, hovering a little higher little lower from then on out.

Now I'm not expert on classic engines so the condition of the engine after stopping again when reaching this temperature I'm not sure if they're normal or not. After reaching our stop I lifted the hood to let it cool down a little, there was white/grey some coming from the oil breather, a dribble of coolant coming from the radiator overflow tube, and the inside of the radiator was making a gurgling sound every say.. 2 seconds.
By miker - 4 Years Ago
I don't remember your previous post, but just a couple,comments.

The factory gauges are notoriously inaccurate.

The oil breather will show vapor after a long drive, with the oil warmed up. That's why I prefer a PCV system over a road draft tube, and a closed PCV over an open one.

If you shut the engine off hot, it will heat soak and gain temperature at the top of the thermostat housing and the radiator. That can be the gurgle you hear. If you don't have a catch can and a sealed radiator cap, you'll end up with air space at the top of the radiator. If you fill it, it just repeats the process. Keeping air out of the system, using coolant recovery, is what most modern cars do. But they're designed to run over 200 degrees or so.

Go buy a cheap infrared thermometer. Check the temp at the top of the radiator and the themostat housing. Then, you'll know where the engine is running temp wise. You can check the bottom of the radiator too, and see the temperature drop. It's hard to believe, but I've seen several of these cheap ones run within 1/2 degree of a really expensive Fluke meter. Typical one from Amazon.


You're probably just fine if your running a 50/50 mix of antifreeze and a 10lb cap or so.
By DryLakesRacer - 4 Years Ago
I agree totally with miker. I have a meter like that from Harbor Freight and would never travel with out it. Great to check tire temps too. I do not have a recovery system on my 56-292 and always leave the coolant level down 1" . I learned the hard way with that, it was always pucking out a small amount of coolant if I didn't. I use a #7 cap.
On your short trips does the temp gauge slow come down on a down hill run. If it does your probably ok. Good Luck.
By GREENBIRD56 - 4 Years Ago
If your engine was really "HOT" it would be boiling over - not just a little overflow - a lot. The gauges can be "re-tuned' to read a bit more accurately - but making a check with a real thermometer - infrared works best - to settle your digestion.....is a good idea. Overflow space is exactly as DLR described above - leaving room in the upper tank of the radiator.

I'll try to hunt it down - but I used to have a photo of the opening on the back of the temp gauge where the needle position may be adjusted. The opening shows the edge of a cogged wheel where a small screwdriver can engage a tooth at a time. We had an ancient "wind-up" alarm clock that adjusted speed the same way, if you've seen one. 
By paul2748 - 4 Years Ago
Another way to check temperature at the radiator is to use an old fashioned thermometer (meat or one from the parts store().  Warm the engine up to where the gauge usually shows (don't put the cap on) and stick the thermometer in the water
By Half-dude - 4 Years Ago
Hey sorry for the delay,

Thanks to tall of you for your advice, it really is helpful and put me at ease some.
I've actually tried that temperature gun trick last year on the car, but that was before I put a colder thermostat in. but I think I remember the engine being around 190/200 degrees.

So do most of you guys use aftermarket gauges?
By petew - 4 Years Ago
I put an aftermarket gauge in my 1955 tbird long enough to establish exactly what temp it was running at when fully warmed up which was 170 degrees. The factory gauge was indicating at the top of the white zone at 170 degrees. Seeing the gauge up so high was upsetting so I removed the factory gauge and very gently bent the needle towards the cold range . At 170 degrees the factory gauge now points right in the middle of the white zone .
Guess that was a "calibration" that I performed.
By charliemccraney - 4 Years Ago
190/200 degrees is nothing to worry about if it is stable at that temperature.

A colder thermostat is not generally a good idea.  It will have little, if any effect on the temperature because it controls the minimum operating temperature, not the maximum.  If you have some problem causing it to overheat and it is not actually the thermostat causing the problem, then it is still going to overheat.  A colder thermostat will reduce efficiency and increase wear.- not by an alarming amount, probably not even significant enough to be a concern for the typical collector vehicle, but increased wear nonetheless.

I use an aftermarket gauge mostly because the factory one never worked in my ownership and the wiring under my dash is a mess.  The thing I do like about a gauge that actually indicates the temperature is in the event that something does happen which results in the engine running hotter than normal.I can use the gauge to determine if I can make it home or need to call a tow truck.
By oldcarmark - 4 Years Ago
I have a quality Aftermarket  Mechanical Temp. Gauge under the Dash along with Oil Pressure, Voltmeter, and a Vacuum Gauge(Mileage Minder). I drilled and tapped Intake Manifold  behind the Thermostat Housing to get a very accurate Temp reading of Coolant leaving the Rad. The Factory Temp Sender is in the Head at rear of Engine. Is that One reading High or Low compared to the placement of mine?
By Half-dude - 4 Years Ago
Well that puts me at ease some then thank you very much!

Can any of you suggest some good models of instruments to use? I'd like to, as well, use one of those Temp/Amp/Oil Pressure clusters. My main issue is finding one where the Amp meter will read lower then 8 (I still have the original 6 volt system).
By Bobwanna - 4 Years Ago

My main issue is finding one where the Amp meter will read lower then 8 (I still have the original 6 volt system).

Looks like progress on you meter issues for Oil pressure and temperature. As for Voltage versus Amps, I believe most newer instrument packs have Voltage meters that are for 12 Volt cars and do not read lower than 8 Volts. The older under dash units usually had a oil pressure gauge and an Ammeter gauge for 30 Amps. I am not sure of any supplier that has a 6V Voltage meter to fit these panels. Maybe someone on this board can knows - Bob
By oldcarmark - 4 Years Ago
Been looking for a 6 Volt Voltmeter also. Not found One anywhere. Buy the best Gauges You can afford. Electrical Type are easier to install but I think the mechanical Ones are more Accurate. Like anything else You get what You pay for quality and accuracy wise.
By 2721955meteor - 4 Years Ago
Most dont seem to get the mesage that 200dgs is not hot,with even a 6 pound cap watter wont boil. hot water is more  eficent  in rejecting heat it the rad. like several posts if your rad is not boiling  over you are not in cricis. I have 2 water temp gauges 1 atback of head 1 at therm end of int. ther is alwayes a differenc of 10 to 15,as the heads create most of the heat, so with the inacurat factory guages 
sender at coolest part of the head, the temp at therm is quite diferent .guage should be at the therm end of intake giveing the temp of both heads and if you have 200dgs ther you are perfect. just my take on it all. 
By Half-dude - 4 Years Ago
Thank you! I'm happy to know that now. : )
By GREENBIRD56 - 4 Years Ago
At its current stage of equipment, my outfit runs 100º over the ambient temperature - decreasing down to the thermostat opening temp of 185º. This is a result of a series of tests where I either did a "burn down test" at idle in the driveway - or drove the car and jumped out with the infrared thermometer. All of these readings were taken at the thermostat housing - just to be sure they were relevant to each other. Like clockwork - on a day where its 106º or 107º in Tucson - the infrared shows +100º. The 200º+ numbers don't seem to have had any ill effects - other than trying to cook the carb or firewall. I'd like to have a bit more than marginal tolerance - but its going to take a better radiator than the shorty T-bird stocker and probably a more efficient water pump to feed it.

Make sure your radiator has decent fluid in it - and use anti-freeze "coolant". Where pure water will boil at 212º (at sea level) - Ethylene-Glycol 50/50 mix will run the boiling temp up to 223º in an unpressurized system. You get about an additional 2.5º per PSI from the radiator cap - so a 6 pound cap is worth another 15º. The combination of the two will make the system "safe" (from boil over) to 238º. The worst ambient I've seen around here is 126º on the 101 freeway in Phoenix - so it was getting close for sure.