AH c'mon have a thick skin.

 

Started on the line and run for a quarter mile.

You have to factor in airflow through the radiator to come up with an optimum coolant flow rate.

..

Once again, how long do they run?


My, isn't he brave in a PM.

 

I would like to see this anonymous person defend his statements. Nothing more.

 

I have to question if the quoted person has ever seen a radiator out of a cup car? The ones I have seen were pretty large and about 5 inches thick; which really helps with the surface area of the tubes. I have to fall on the side of needing a larger radiator on this one. When I went from a mild 350 to a decent 406 I just couldn't keep the temps down and had to go with an aftermarket unit. Now you guys are all right in your own sense; the btu output will increase as power output increases, so under load the engine will produce more waste (heat). Now on the other hand, at idle the cooling system might handle it and even at part throttle maybe but you will see the temp gauge race up when you pour the coals to it! Just my .02 and if it was me I would run the stock unit and monitor the temps closely just to avoid damage; it will want to get hot for sure, it's just when and under what operating conditions. You may not see those much and it might be something you don’t want to change out.

P.S I run a stock heavy duty unit in my personal vehicle that we talked about the other day on the phone and it does ok around town (no AC) with a big flex fan pulling air in, but shoots right up in temp when we put some power down. And one more thing, cars like top fuel drag cars and such that don't use gasoline don't have issues with heating up; we run 900 hp sprint cars with relatively teeny radiators, switch them to gas like they did with modified’s years ago and cooling becomes a huge issue. Sorry for the long post. How's the engine coming along?

 

The HP /BTU analogy is mistaken. Anybody can find 1 hp =2547BTU but that is max HP all the time. Unless you drive with the pedal to the floor 100% of the time it means nothing. It does make me wonder about HP vs. displacement though. I wonder how many guys have upgraded their 350 to 383&396 and needed a new radiator. Does HP actually determine the need? Heat is dissipated via the block,oil and coolant not just one. That part about the flow was interesting it could go either way more time to cool in the radiator larger surface area or more air flow would do the same thing.JSUP how many ponies do you expect to be pushing when it is done?

 

Have you ever seen the radiator in a Sprint Cup car?

It would dwarf the one in your Vette.

He's talking out of his **** orifice.

 

It wasn't an analogy. It was a statement in thermodynamics.

I think I will intentionally make an incredibly bogus statement as fact so you can jump up and down and salivate on your keyboard.







Not!

 

I don't profess to be any kind of expert anything. However, volumetric efficiency relates to how well the cylinder can fill, i.e. how close to ambient pressure it ends up at. Exhaust, I can't say I've ever heard that term? When the piston is fully up at the end of the exhaust stroke, any exhaust has moved out of the way whether it wanted to or not, whether the head is great or not. Is he suggesting on GM **** engines that a bunch of exhaust is left in the cylinder?

The exhaust stroke on your uber efficient motor takes just as long at a given rpm as it does on a GM *** motor. So I fail to see how less heat would soak into the engine in one vs the other, except of course that the GM **** motor didn't have as much heat to begin with since it doesn't breath intake air as efficiently.

Really, though, what's the point here? If it's that you don't want to upgrade your radiator, don't. There's certainly a chance it will be acceptable. And if it's not, you'll notice and fix it.

 

The point is an attempt at a civil exchange of information and opinions. As happens all too often here, someone gets their feelings hurt or spouts crap and the thing goes to hell.

It never ceases to amaze me the things people will say to another, safe in the anonymity of the interweb, that they would never say to their face.

 

The point is one of discussion. Someone mentioned at some point cooling may be an issue. I got differing opinions and threw it out to the floor for discussion.

I never had any intent to swap out the stock radiator until I see the results. I alreday did that listening to people tell me about headers and heated O2 sensors, which turned out to be a bunch of crap....ran fine with stock O2 sensors, and ran with codes on heated ones.

SO....I wasn't asking advice, I was spurring discussions.

 

For reasons I refuse to get into, the guy who sent the PM can not post in a thread that's a pissing contest. It's perfectly reasonable.

 

A 19x31" radiator is pretty normal for a stock car radiator. Its pretty normal for a chevy radiator. The more heat you generate the more surface area you need to exchange it.

Also the less airflow through the radiator the larger the radiator needs to be. NASCARs have lots-o-airflow throw the radiator to help exchange even more heat, same with most racing radiators. The C6R radiator is tiny compared to my stock trucks radiator.

The improved cooling of the dart block is just that it gets more heat from the motor into the water in the appropriate places to prevent hot spots and the like. Once that water is out of the block it has to be released into the atmosphere. So you are going to need a heat exchanger upto the task. This does not answer the question of whether or not your existing radiator is up to the task or not.

Full Disclosure: I have a dewitts aluminum radiator and spal fans on my C3. It sure as heck cools my C3 a lot better than the stock brass one did. And it is around 19x31.

The simple answer is that you are burning more air/fuel with more surface area to absord it, and you even said the block was better for cooling. Which all means there is more heat in the water, and that heat has got to get out of the water.

 

It's been my experience that there is no shortage of misinformation when it comes to exhaust sizing and radiator/cooling system sizing. So far MK 82 and Guru are making the most technical sense here.

 

Oh give me a break. What you are saying is that he cannot get a point across without vulgarities or insults. Sounds like he has a history.

His input is welcome here but he has to be able to back it up.

 

put it together, keep your $600 in your pocket.

if it runs hot, remove the $600, and replace with aftermarket rad.

 

winner!!!!

 

werd!

 

I don't usually jump into the middle of debates like this -- but here goes ....

MK 82 is correct to point out that the amount of heat energy that is generated is governed by the laws of thermodynamics.

A 427 engine displaces 22% more volume than a 350. For the sake of argument (and simplicity), let's assume that both engines run at exactly the same air fuel ratio, the same volumetric and thermal efficiencies, and have the same combustion characteristics as a bone stock L98. That being the case, the 427 will require 22% more fuel to maintain the same AFR as the 350. The total amount of energy released by the fuel during combustion will then be 22% higher in the 427. Since this example assumes the thermal efficiency of both engines to be the same, a 427 will generate 22% additional waste energy that needs to be dissipated by the cooling system.

This is very simplistic, obviously, and is only based on the difference in displacement. A high performance engine such as what John is building will generate significantly more heat over and above the heat related to the displacement difference due to the power levels he wants to achieve (more power = more airflow in/out = more fuel). It would not surprise me to see the maximum cooling system load increased by 30-40% compared to the L98.

My personal opinion is that the stock cooling system most likely won't be able to cope with the additional heat under high load conditions (hot day idling with the air on, extended full throttle blasts, etc), but I think you could leave it stock for the time being and monitor it closely while you get the tune dialed in to see how much cooling margin (or lack thereof) you really have.

 

I didn't read all of this (so forgive me if I repeat anyone), but I saw you guys talking about thermodynamics so I thought I'd pop in. I've taken a few thermodynamics courses, an automotive HVAC class (so we did tons of heat exchangers), and an internal combustion engines class. Most of these were engineering master's courses, so these are theory and practice courses...not a "how-to" discussion.

The bottom line is that about 1/3 of the energy from combustion goes into heat. GM sized the Corvette's cooling system for a certain amount of heat rejection. If you make 50% more power than GM designed for (so 50% more heat), you need to increase your cooling system's heat rejection capability by 50%.

Remember, GM may have designed a 50% safety factor into the cooling system...so you could be running on the ragged edge of safety for this assumption. You do not have to install a higher capacity radiator, however, to attain this (though this is the easiest way). For a few hundred bucks it is definety worth it. People can talk all day about how they ran this setup and that setup successfully, and there is no questioning that...but I'm not the kind of person to look at an 80 year old person that's smoked all their life without having cancer and think that this is the benchmark for a healthy lifestyle. It should be fairly easy to ballpark what GM sized the cooling system for, as the thermodynamic equations for cooling fins are well known and some air speeds, humidity, and temperatures can be assumed. If you're curious shoot me a PM and I'll dig out some of my old books when I get a chance.

 

Oh and if you read through all the tech tips from the link I posted you will also find that the keeping fluid in the radiator longer is also an old myth. When you keep the fluid in the radiator longer your also keeping the fluid in the block longer so there is no gain.