I've read some guys comment that a cooler running engine is better for performance, but I must disagree. One of the first things we learned in auto shop was that the coeffeicent of friction between an iron bore and an aluminum piston is best at about 225*, and the bore wear is terrible at lower temps. If you are sucking all the heat away and throwing it at the radiator, you have less heat to push the pistons around. I am all for running as hot as possible without overheating. I run a 205 stat with an A/C style water pump and a 4 row radiator, no problems so far. What about the rest of y'all ? DF

 

I was going to rebuild an inline six one time and the #1 cylinder had much more wear than the others. #6 wasn't that great either, and somebody told me this was because these cylinders on the ends run cooler thus wearing more. This is also why the lt1,lt4,ls1 run like they do. They use reverse flow cooling where the coolant enters the head first and then goes down to the cylinders, letting them run very high compression ratios with aluminum heads.

 

well if that was true why do drag racers ice down there engines in between rounds?? if they ran better hot then they should let there cars idle in the pits and never shut them off. the cooler the engine runs, the engine gets a cooler denser charge of air in the cylinders thus making more power.. i run a 160 degree therm. in my 472 and it runs better than the 190 especially in the summer heat. do you own any high performance engines?? i'm curious on your point that the hotter a high performance will not detonate, are you sure? have you ever experimented with this point? ....

 

The comment was about engine wear. Drag racers rebuild their engines constantly. Any comparision between a drag racer and a street truck is irrelavant in this discussion. How many drag racers do you see with 200,000 miles on an engine?

Ken Payne

 

i'm not responding to the comment. i'm talking about the very first question he asks! when he disagrees. and where not talking about N.H.R.A. where they have to rebuild every round. have you ever been in the drag racing scene. there are lots of people that go a whole season without having to totally rebuid there engines. i've seen and talked to people years ago when i use to hang around strips. now it may not work for all, but for the people who know there combination that's all it takes, change plugs, oil, adjust rockers(if app) and minor routine maintenance. and above all cool down between rounds to make peak horse power when the time comes. i'm not worried about 200,000 miles. i'm answering the question that a COOLER engine will make more power than an engine at 225 degrees.................

 

There's cold, there's hot and then there's way too friggin' hot! Engines don't like either end of the spectrum, and the magic middle should only be about a 25 degree range. You have to cool drag racing engines to get optimum performance because if you didn't they'd end up in theProfanity RemovedH range in a few passes. Running an engine at WOT over and over again without cooling it down is not conducive to making it live very long and cylinder wear will be the least of your concerns.

As far as what the optimum operating temp for an engine is depends on where you live, how you drive and what year your engine is. Newer engines run hotter than older ones to mimimize emissions and because they tend to run leaner due to the constant monitoring of EGO by the ECM which adjusts the A/F mixture. A lean engine gets better fuel mileage, has more power and produces less emissions but runs hotter. An older carbureted engine which runs fatter will generally run cooler but get poor fuel mileage, have less power and produce higher emissions. Running the engine hotter is not a bad thing as long as the proper A/F mixture is maintained and the cooling system is adequate and in good shape.

 

A cooler engine won't, cooler air stream will. If the intake track is cooler (a by-product of a cooler engine), then the incoming air will be. Colder air is denser than hot air which can give more power since an engine is an air pump. Also, remember that many dragsters have limited cooling or oiling (ever heard of people concreting oil passages so they can punch out the bore?) so cooling them between races makes sense. I don't know of many people defeating oiling or cooling sytems on the street. Probably the best thing you can do is to make sure your air intake track stays cool one way or another. Reducing under hood heat can help but the purpose is cooler air, not a cooler engine (to a certain degree --- you certainly don't want a engine so hot that the exhaust glows!)....

Many people will put a cooler thermostat in to keep an engine cooler. The gain does not come from the engine being cooler but instead from fooling the computer into thinking the engine isn't warmed up and running the system rich. However, this just defeating emissions laws and can cause other problems as well.


Ken Payne
Ford Truck Enthusiasts Admin

 

Great topic! The idea is to run cooler fuel, hence the reason for using cool cans, for increased performance, but I'm pretty sure there's more to running a cooler engine then that. The benefits aren't just for computer control motors either. There is a "happy medium" temperature in which the fuel is cool enough to prevent perculation which may cause a possible vapor lock problem, and hot enough to atomize the fuel running threw the ports. Other possible benefits with running cooler temps I would think could be from higher viscosity of the oil, creating a tighter fit between surfaces, even though most motor oils are suppose to be immune from any viscosity break down. Some tired engines tend to make some noise on cold starts do to the oil having to run threw the passages before lubrication, but at higher temps, they all seem to make a little noise from having a little more clearance then needed. One more thing I'd like to add is that the performance of an engine isn't directly proportional to the life expectancy of it, when it comes to engine temp, but the idea is to find the half way point.

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Actually you concrete the coolant passages not the oil passages. Most purpose built alcohol and top fuel engines have no provisions for coolant in the engine but those are the types of engines that get torn down pretty frequently also.

 

cj, I think drag racers ice down the engine between rounds because it gets hotter than my ideal 225 during the race. Some of these guys have a much too small radiator to save a few pounds of weight. Lots of them bring an engine up to temp before racing, I have not seen anyone starting cold and then pulling up to the start line. Many of these guys are boiling over at the end of a run. If they were running a 50/50 mix like most of us that would be hotter than 265 to boil. As Ken said however it is the block and heads that I like hot, it is best if you can keep the fuel cool and duct in some cold air from the grille, rather than breathing in hot under-hood air. DF

 

I have a magazine article I'll have to dig up, I think it's a Hot Rod, anyway they did a dyno test with a 460 (imagine that they didn't use a Chevy). They tested it with a 190 thermostat and then with a 160 thermostat. Allowing the engine to cool properly between runs and then warming it up to operating temperature before the actual test. The 160 thermostat run gained 30-something hp. That was the only change they made. It is vital to keep an engine cool. Too cold wears more, too hot hurts performance. Most high performance big blocks don't have any trouble getting warm enough even with a 160 degree thermostat.