Technical ZZ4 operating temperature

Have a ZZ4 crate engine in my 49' Mercury Sled. It runs 205-210 degrees on hot summer days. Is that normal? Concerned about overheating.

 

That's fine.

 

I had several ZZ series motors and they all ran 200-210 in a 32 Ford. My favorite was the first ZZZ. Made so dam much noise when you first started it you thought it was gonna disintegrate. Ran like a striped ape and lasted about 40,000 miles before it needed a refresh. Wish they would bring back those motors.

 

Perfect

 

temp result of many factors - radiator quality, etc

 

I have a ZZ3 in my 47, as long as we're moving it runs a nice 180* - 190*. Parked and idling, or slow moving like in a traffic jam the temp creeps up to ~210, but so far has never overheated before we start moving again and the temp comes back down. So far no actual over heating, but it does make me nervous to watch the needle go higher and higher, not knowing if it is going to reach a certain point and stop there, or if it will overheat, blow head gaskets or start seizing pistons.

 

Later model engines were designed to operate at higher temps because of emission considerations, but honestly its not good because you increase wear on components and you have much less of a cushion if a problem does arise. Don't care if they say the coolant won't boil till it gets even hotter because the system is pressurized........its still better to be operating at 180/190, especially in the rarified air in Colorado. I'd look into finding a way to lower the operating temp. What thermostat are you running?

 

I was always running Walker Cobra radiators with my ZZ motors because of clearance problems in a deuce with a stock firewall. Probably should have been using the Z series?

 

Also depends where the temp sending unit is.
The head or intake.
Head readings are always higher.
As far as extra heat causing extra wear, the later versions of the gm SBC were born with 195 thermostats and probably averaged a lot more miles than the older versions. Been around a lot of em with over 250k on em.
We’re also incredibly clean when torn down.

 

It has nothing whatsoever to do with emissions controls.

Complete combustion, meaning both maximum mileage AND maximum performance do not happen under 195° coolant temperature.

On a classic pre-LS and pre reverse flow SBC, that number is closer to 205°.

That's not speculation, or straight-up guesswork.

That's right out of the GM design specifications.

This is why the design specifications call for a 180° thermostat, irrespective of elevation.

 

I'd like to know how an additional 15 - 20* temperature in the cooling systems causes an increase in wear of components. I mean, if the pistons swell to the point they start to kiss the cylinders, yeah, that's an increase in wear. Or if head gaskets start failing, there you go. But barring those obvious extremes, how does running at 205*- 210* degrees cause an increase in wear vs 180* - 190*?

 

A mid 50's small block had to be rebuilt at around 70/80 K because it was worn out normally Now we start thinking about an engine needing work around 200K .

The thing here is the nonsense of it is an old car so a dude is scared shitless because the engine wants to run at it's operating temp that it is designed for rather than what he thinks it should run in an old car.
If that engine were stuck in a late 70's Camaro the temp gauge would read normal as that is it's normal operating temp.

 

It doesn't.

Worse, failing to achieve the higher operating temperature, or taking longer to get there, means that the engine is operating for longer period of time before any moisture that is accumulated in the crankcase is boiled off.

That can lead to an absolute disaster over time inside of an engine.

Combustion byproducts that have snuck past the rings combined with moisture will destroy oil.

Moisture alone will erode at the surfaces inside of the engine slowly.

Combine those combustion byproducts with water that hasn't been boiled off and you get acids that eat metal. Those acids will attack the softest mentals in the engine first. You know, things like bearing shells.

I don't know where people get the idea that operating an engine at lower temperature is somehow better for the engine. There is no scientific data whatsoever to support this.

It's the same level of nonsense that comes up every time PCV systems are discussed. Those aren't just for emissions, they are also to preserve the life of the engine so that the manufacturer can actually give it some sort of meaningful warranty.

 

The “P” in PCV isn’t pollution. I still deal with that with students.
As far as temp, the factory specs is where I start. Radiator cap and thermostat.
A flathead seems to like cooler temps. Most OHVs seem to run hotter. A newer crate engine should probably run the temp normal for that engine. If the OE used a 195 t-stat then why should the temp stay below that? Why would you want it too?
One reason the idiot lights and gauges without numbers came about was to keep folks from freaking out.
The “my oil pressure is below 20 at idle when hot, what should I do” or the “my temp rises 10 degrees at a stop light” worries were averted.

 

I had a small OT Italian car that has a gauge calibrated with temperature. The needle would creep up if you stopped for a while, were going slowly in traffic or were wringing its guts out at high speed.
That was normal, and IS normal. So long as it wasn't in the red, any of the white numbers were fine and expected.

The following model had the gauge controlled by the injection computer; it just crept up slowly until it got to the middle of the gauge and would stay there unless the engine was about to overheat, where it would put the needle into the red and chime.

The model after that just had a red light.

There's progress for you.

 

Yes, and many of them come from the factory with built in oil coolers and transmission coolers. Add to that the fact that they are being continuously monitored by a computer that not only senses the engines temperature, but has sensors that detect knock and retard the timing to prevent detonation. Many have steam venting because some of them trap air in the coolant system in the worst places.....the top of the head. They also have roller cam components that the ZZ doesn't have and even better gerotor oil pumps. Oil viscosity changes with temperature so its thinner and less protective of rubbing and rotating compoents. If oil films never broke down and were completely able to always be where they need to be, wouldn't parts never wear out? They do however wear, and any extra space someone has before their engine reaches a catastropic temp is added benefit. Yes there have been millions of them that have gone very high mileage.........and many that didn't. Also add to that that ALL of the newer vehicles since about 1990 have utilized overdrive transmissions that allow those high mileage engines to operate at lower rpm levels mile after mile. Some of the higher performance ones even have oil squirters under the pistons to try and avoid detonation. Then there is that "thin" air where there is less mass passing through his radiator........ not like the denser air in Alabama.
Sorry Anthony, but there are a lot of reasons why later model engines survive at higher temps.......and none of them are present in a typical old school Chevy in a lead sled.

I believe in the old saying "Better safe than sorry", so if we can agree to disagree, I'll stick with prefering lower operating temps and respect your opinion differs from mine.

 

The 195 stat was placed in non roller applications as well by gm.
Steam venting has been around long before EFI
As far as oil, running one cold causes issues as running excessively hot. I’ve torn into engines full of sludge with less then 30k on em due to running too cool.
I’ll run em “hot” you run em “cold”
I’m good with 210 on a sbc all day long

 

Thankfully we don't need to rely on opinions, and can just stick to facts!

It never ceases to amaze me what those who have never studied this particular science say out loud.

 

I’m no scientist.
The flathead for my sons jeep will get the temp stat and pressure cap that Willy’s used. Then any heating/cooling issues go from there.
A modern engine (crate sbc here) in an old car should run the temp the designers intended.
Had an alignment shop say they couldn’t line up a 40 ford once. The owner had installed a newer suspension The shop couldn’t line that up to 1940 specs.
I’m not a scientist but I try to apply common sense.

 

I'd say that the biggest change that added mileage to motors wasn't temp running higher but EFI, computer controlled EFI.

With that came no more leaking carbs drizzling fuel into cylinders and washing the oil off of the walls and piston rings. Neither was running rich a problem anymore, again washing walls and rings.

99.9 percent of the time when a old carb goes bad it goes way rich either thru worn parts, bad gaskets, leaking floats, dirt etc and this constant washing of gasoline cleaning off the oil of the cylinder walls and rings, forcing a basically dry rings against a dry cylinder, over and over at each start up, especially those bad enough to have to set and crank and crank due to the fact that either A: the fuel bowl is empty due to it leaking out or B: the engine is flooded due to the carb leaking. Then the amount of wear is greatly increased.

The second is oil, oil has came along ways since 1970, both in its ability to lubricate, example? Almost impossible to seat new rings with good quality synthetic oils now days. And the ability of oil to stand up better before breaking down and oils ability to produce less sludge just due to its make up alone.

I'd say that these 2 things in this order had more to do with the mileage we see today out of modern engines more so than raising operating Temps 15 degrees.

 

Yep. And raising the temp didn’t hurt anything all those extra miles.
Which is precisely the point.

 

Improved mileage has been as a result of a number of changes. Higher operating temperature is not the main contributor, but it is part of the 'package deal'. It is a fact that gasoline burns more efficiently at the raised heat levels.

As for what has been the major factor for increased mileage, I would say it is overdrive transmissions..........

With the ZZ4 engine operating temperature question, what do they run at when in the factory vehicle?
Find out, and then set yours up to match. Can't go wrong.

 

You have to "click to expand" to see the complete replys below.

So engines with high temperature thermostats never get any moisture in the oil????? Cept maybe when they blow a head gasket in Arizona on a 115 degree day.

I think you or someone mentioned somewhere that the higher operating temps weren't because of emission regulations.....but rather for efficiency. Why do you think the car manufacturers worked so hard to increase mileage? Its because they were mandated by the EPA to meet certain average gas mileage minimums thereby reducing gas emissions. I'd call that somewhat "related".

Don't need to study science, just read the parts manual and Motor Trend.



Below is an article from Motor Trend where they tested thermometers on an engine dyno and lost both HP and Torque with a higher temp thermostat on a high performance engine.

https://www.motortrend.com/how-to/how-to-choose-a-thermostat-for-your-classic-car/#:~:text=A 180-degree thermostat is,bit more horsepower and torque.



This is the source for GM info for ZZ4 thermostat
https://www.chevrolet.com/content/d...ne-long-block-installation-guide-24502609.pdf

 

Yep. A 180 stat. Running 200-210 sounds about right for summer driving.
The 190-195 stats generally run 210-220ih. Maybe a little higher.
Starts opening at 180. Probably full open at 190.

 

This is a simple explanation of what a thermostat does.
At about 20 degrees above its rated temperature, the thermostat is fully open. It opens and closes gradually to maintain proper engine temperature, which can reach 250-275 degrees under some conditions. The thermostat is at least partially open at all times once the engine warms up--even in sub-zero weather.
If a ZZ4 engine is intended to use a 195* thermostat, then 205 to 210 on a hot day is fine.
@gimpyshotrods and @anthony myrick nailed this in posts #2 and #4....... Smart guys.

EDIT: A document in this thread show that a ZZ4 is recommended to use a 180* thermostat. The OP's temps on a hot day are still fine.

 

That might be a little difficult since the ZZ4 is a GM Performance Crate engine and was never offered in a factory vehicle.

 

Damm, now you tell me. I just waisted 40 years in science and engineering.

 

Isn't it basically just a tweaked crate replacement 350ci with aluminum heads and intake, compression boost and roller cam available direct from Chevrolet? Soooo..... they should be happy at the operating temp of a factory 350 of the same era, no? If your science and engineering background disagrees, please, take the 'talking stick' and enlighten us. What temperature range should a ZZ4 engine operate within? I am genuinely interested.......

 

That's ok. I'm sure you can Google the ZZ4 specifications and get the answer. I have to go renew my Motor Trend subscription