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Old 05-17-2020, 01:03 AM
JLBIII JLBIII is offline
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Default Running too cold?

Picked up my 68 Firebird this past Feb. It's a numbers matching car with a 400 HO. Spent the past 3 months cleaning up, replacing some parts and fluids, rebuilding Quadrajet, etc. Been taking her out on some road test cruises. I'm running a 180 thermostat. The rally temp gauge in the dash is reading 140 after driving around for awhile. Also running a Thermocap radiator cap that reads the same thing. Put in a new 180 thermostat today and got the same 140 reading after driving over 40 miles. I did see it go up to 150 during some stop and go traffic in today's 80 degree weather.

I am running distilled water with Water Wetter in the radiator for rust prevention. Initial timing is set at 14 degrees BTDC w/ vacuum advance disconnected. 93 octane, no knocking. Using manifold vacuum for distributor advance.

Is it ok to run at that temp?
Thanks

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Old 05-17-2020, 02:44 AM
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No. 160 is the minimum recommended, hotter is better for longevity, within reason. Newer vehicles with electric fans sometimes don't turn the fan on until 210+ degrees

I'd like a "third opinion" on how hot the engine is REALLY getting. A QUALITY mechanical gauge plumbed into the intake manifold would be best.

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Old 05-17-2020, 03:18 AM
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Get a laser thermometer and point it at the spot your gauge is measuring. Need to make sure your gauge is right first.

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Old 05-17-2020, 04:25 AM
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Basically if your thermostat is actually working it's impossible for it to run 20 degrees below the rating of the thermostat. It could be neg 20 outside and it should still run within 5 degrees of the thermostat rating.

At the cap is a bad place to check temp ... it's on the "cold" side of the radiator. If you have a infrared thermometer ... I'd try to shoot the driver side radiator tank to get a feel for average temp of water leaving the engine.

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Old 05-17-2020, 05:42 AM
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If it truly is running that cold then it's not good for the motors longevity, no less fuel usage and power, because heat is power!
A internal combustion engine is running on expanding hot air, so always keep this in mind.

Running that cold means the motor is likely taking longer to warn up then it should and test conducted long long ago prove out that 70 percent of all the ware a engine acquirers takes place between the time its cold and up to normal a normal temp.

The oil temp in the motor needs to atleast get up to the boiling point of water so that the normal condensation that is a byproduct of combustion gets sucked out of the motor.

If your just crusing around with light throttle at 2500 rpm even with a water temp reading of 160 it's unlikely that your oil temp will get up to above the needed 212 degrees for a much longer time then it should!

And the size ( cid ) and main jurnal size of the motor makes a difference also.
On my oil temp gauge I found that my 455 got up to 230 degrees of oil temp near 5 minutes faster at 3000 rpm then my 400 did!

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Old 05-17-2020, 10:36 AM
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We prefer to run our engines on the cool side. Not 140 cool though.

Technically it's impossible for an engine to run 140 if you're running a 180 stat because it won't even be close to opening. A stat forces the engine to run at or near it's rated temp give or take about 5 degrees. The only thing possible in this scenario is the engine running way "above" the rated temp which means you have other issues.

I'd like to see the temperature measured with another gauge and/or shoot the hot side with a temp gun. Something is off.

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Old 05-17-2020, 11:30 AM
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Something like this: https://www.summitracing.com/parts/sum-g1054?rrec=true

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Old 05-17-2020, 11:38 AM
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What thermostat did you specifically put in the car? During the cooler months I have the same problem, car refuses to heat up.

I went with one of those high flow thermostats and it’s junk. On the list right now is to get an oem style/quality stat in there.

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Old 05-17-2020, 12:08 PM
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I'm using a NAPA premium thermostat. The housing is marked MotoRad. Both thermostats are marked 180.

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Old 05-17-2020, 02:35 PM
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What do your spark plugs look like?

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Old 05-17-2020, 05:38 PM
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Try turning on the heater .... at 140 it would just produce luke warm air.

Like everyone else ... I would suspect the gauge. The cap gauge should read around 140 or less ... it's on the cold side of the radiator, and the factory gauge, unless it's been rebuilt is probably no where close to correct.

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Old 05-17-2020, 06:31 PM
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Spark plugs look good.

Blower motor not hooked up yet. Car originally had ac. Has ac delete now.

Car is down for this week. Rag joint needs replacing and have brake fluid leaking from between back of master cyl and booster.

Going to get laser thermometer as suggested and take readings after repair work is done.
Appreciate the replies!

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Old 05-17-2020, 06:56 PM
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Quote:
Originally Posted by dataway View Post
... and the factory gauge, unless it's been rebuilt is probably no where close to correct.
From what I've read, that's typically the temperature sending unit's fault (even
GM replacements). I'm just parroting info I've gleaned from Peter Serio's posts,
he likes Lectric Limited for senders, and he's THE gauge guru.

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Old 05-17-2020, 07:07 PM
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My '72 LeMans ran at 160 °F today with an outside temp of 72 °F, on the highway running 70 mph. I used to run a factory 7 blade fan with a Hayden clutch, 160 °F Tstat and it would get over 200 °F idling on a 90+ day. I took the stock fan/clutch out and replaced it with a 7 blade flex fan and it would not get above 165 °F on a 90 °F day. I changed the Tstat to a 180 °F and now it gets up to 175 °F on a 90 °F day. The heat is hot even when it's running at 140 °F on a 50 °F day so it is opening. I am going to try a 190 °F Tstat to try to warm it up.

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Old 05-17-2020, 07:43 PM
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I have a 5 blade flex fan and no shroud. Also tried another sending unit.

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Old 05-17-2020, 08:05 PM
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Does a '68 Firebird have a vertical-flow, or a cross-flow radiator?

The big advantage to a cross-flow rad is that the pressure cap is on the cool side, where a vertical-flow rad has the pressure cap on the hot side.

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Old 05-17-2020, 10:17 PM
Navy Horn 16 Navy Horn 16 is offline
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Quote:
Originally Posted by steve25 View Post
If it truly is running that cold then it's not good for the motors longevity, no less fuel usage and power, because heat is power!
A internal combustion engine is running on expanding hot air, so always keep this in mind.


The oil temp in the motor needs to atleast get up to the boiling point of water so that the normal condensation that is a byproduct of combustion gets sucked out of the motor.
That's nonsense, and not even close to accurate.

Heat is power? LMFAO. Why the hell are racers doing everything they can to keep their engines cool? COLD AIR makes power, because it is more dense. The cooler the engine, the cooler the carb and the intake, which makes more power. Good grief, you couldn't be more wrong.

Oh, and oil doesn't have to reach the boiling point to release any condensation. Ever spill water on a sidewalk on a hot day? What happens to that water? Do you think the sidewalk is 212+ and the water sizzles off? No. And that's at atmospheric temp, not at a vacuum like any crankcase should be (which lowers the vaporization point).

The temperature that modern engines run at has nothing to do with heat making power. It has to do with emissions, and CAFE standards. 140 is a little on the cool side, but it isn't going to hurt anything.

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Old 05-18-2020, 04:18 AM
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Quote:
Originally Posted by 242177P View Post
From what I've read, that's typically the temperature sending unit's fault (even
GM replacements). I'm just parroting info I've gleaned from Peter Serio's posts,
he likes Lectric Limited for senders, and he's THE gauge guru.
I'm sure Peter is correct .... and yes the obvious far easier to replace the sending unit than rebuild a gauge.

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Old 05-18-2020, 06:08 AM
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Navy horn your comments prove that have no clue as what in accutality takes place when a air and fuel charge injested into a cylinder gets ignited and the burn / flame front starts to expand.

The level of heat that is produced when the flame front starts is the sourse of power!

When steam locomotive engines where able to get away from the old slide valves they used and go to poppet valves engineers then found they where able to do / apply what they called super heating.
This is where they send the 400 degree steam back thru the boiler again and bring its temperature up to near 700 degrees, this in turn allowed a given volume of steam to do more and more work equals more power, and it's the same dam thing as it relates to the burn rate in a combustion engine cylinder!

Yes you need to injest the coldest air and fuel possible into a combustion engine cylinder, but at that point of ignition things change over to a whole other set of factors!

And if we are talking about maxing out power then emissions and CAFE standards needs to stay out of the picture.

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And he was not talking about 1/8 or 1/4 mile ETs!

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1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!

Last edited by steve25; 05-18-2020 at 06:48 AM.
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Old 05-18-2020, 08:30 AM
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Default 170* T-Stat

This is any interesting topic. I started my Pontiac Journey acting as ‘scrub nurse’ for my older brother and his best friend on the weekends while they worked on their Pontiacs. This was circa 1983. Back then, HO Racing and Nunzi were the only players at the table for aftermarket Pontiac Performance. And I remember both offering ‘cooling kits’ as an introductory upgrade that included 4-row factory style radiators and 160* T-Stats. My brother and his buddy both had 160* T-Stats in their cars - which ran notoriously ‘warm.’ Maybe the 160 stat was a crutch for an inefficient water pump? I will say, my brother’s car had quite a bit of compression for the street by today’s standards: 670 heads on a 428. There were no aluminum heads available back then. I believe his friend’s car was a ‘bit’ more pump-friendly with a set of heads from a 350 on his 400.

Fast forward - when I first got my Red 73, she got SO hot the first night I took her to a local cruise night that she literally vapor-locked and died right there in 4-lane traffic. I limped onto a side street, threw the hood, and sat for about a half and hour and then limped her the rest of the way to the event. By the time the sun went down (along with ambient temps) she ran fine - albeit pretty warm - all the way home. Of course, I did the kitchen sink routine: 4-row factory style radiator, Flow Kooler water pump and 160* stat. That car will run virtually dead on 160* (verified with a heat gun) form the coolest days in fall and early spring all the way up to the hottest day of summer that I’m willing to sit in a car with black vinyl interior and no AC. Point is, the current low-tech cooling system is incredibly reliable.

But I have often wondered if the car would run more efficiently at another 10* of operating temp? I just have never wanted to leap back into a 180* stat only to find that she pings and chugs after I turn the key off on a hot day. I always wished there was an option for a 170* stat rather than taking a 20* step to see what happens.

In reading this thread, I did a bit of a dive reading posts on other forums and I found a supplier who sells Custom in-house built 170* stats for virtually all makes including GM / Pontiac. If you back track from this link, there is a ton of info on this site about how coolant temp affects performance:

https://www.lethalperformance.com/re...hermostat.html


Last edited by PDC; 05-18-2020 at 08:37 AM.
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