[Z Code 400]

Well TransAm525,

I can’t even begin to tell you how many engines I have torn down over the years, including the old 272/292/312 Fords with well over 100,000 miles on them, some of which never even had a thermostat and still had negligible cylinder wall wear.

We flogged our 429 over 100,000 miles pulling our race cars and we had a ‘hollowed out’ thermostat body in that engine and yet, with coolant temperatures as low as 140° under load, we had less than .006” taper after 100,000 miles of towing. I think that is a fair representation of testing.

If you have ever watched BMEP’s on the dyno I think you would have to agree that an engine will display the highest level of fuel efficiency where the BMEP’s are the highest.

Keep in mind that cylinder wall and piston crown temperature are drastically different than coolant temperatures. The average piston crown temperature will average 600°F and the primary reason coolant temperatures are elevated is to reduce emissions.

The stringent CAFE standards have led environmentalists and manufacturers to concentrate efforts on the development and production of high fuel-efficiency cars. Chrysler recently discovered, through extensive testing, that more uniform cooling of the cylinder walls enables lower average temperatures and simultaneously, enables more uniform dimensions and reduced friction. However, it was necessary to elevate the coolant temperatures simply to hold exhaust emissions at a level acceptable to relevant standards.

Ed Newman of Amsoil recently wrote, "Cooler engines resist stress and wear. As a result, engines last longer, perform better and require fewer repairs."

This would mirror the results we have found through years and years of tearing down and building garden variety street and serious competition engines...Robert

[TransAm525]

Originally Posted by Z Code 400

Well TransAm525,

I can’t even begin to tell you how many engines I have torn down over the years, including the old 272/292/312 Fords with well over 100,000 miles on them, some of which never even had a thermostat and still had negligible cylinder wall wear.

The 292 is the exact engine my 1960 Ford F-100 has. Without a single rebuild in it's entire life, it just turned over to 148,000 miles and is still ticking like new. In the winter (when the coolant temp would drop below 180), the oil temps just weren't high enough to burn the moisture from the oil, thus causing the oil to take on a slight milkshake color. If I blocked the front of the radiator to bring the coolant temp back to 180 degrees, the problem would disappear, and in the summer the problem never surfaced. This all was happening during a daily 20 mile commute with stop and go traffic and 20 minutes of 3000 rpm on the highway during each leg.

Originally Posted by Z Code 400

We flogged our 429 over 100,000 miles pulling our race cars and we had a ‘hollowed out’ thermostat body in that engine and yet, with coolant temperatures as low as 140° under load, we had less than .006” taper after 100,000 miles of towing. I think that is a fair representation of testing.

The flogging is what's keeping the oil temps and cylinder wall temps so high that the wear problem is canceled out. Bronze66's engine probably sees below 2500 rpm most of the time with minor flogging, thus keeping his oil temps and cylinder wall temps low.

Originally Posted by Z Code 400

Keep in mind that cylinder wall and piston crown temperature are drastically different than coolant temperatures. The average piston crown temperature will average 600°F and the primary reason coolant temperatures are elevated is to reduce emissions.

No argument here. But since Bronze66 isn't running the engine at 4000+ rpm all the time, he needs to compensate for the lower cylinder wall temps and cooler oil, hence the higher thermostat to bring the coolant temps up.

Originally Posted by Z Code 400

Ed Newman of Amsoil recently wrote, "Cooler engines resist stress and wear. As a result, engines last longer, perform better and require fewer repairs."

Seeing as he's an Amsoil representative, he's probably talking specifically about the cooler oil temps reducing wear in heavy duty engines (of course using their product) which see extreme conditions and are a large part of Amsoil's market. Running extreme oil temperatures will also create problems of their own.

I'm not trying to start anything here, just having a friendly debate with another Pontiac fellow. I think our perspectives are different because we see two opposite ends of the spectrum. You see engines that are typically ran very hard and heat up the cylinder walls and oil hot enough to not cause wear problems. Seeing as all my engines spend most of their time below 2500 rpm I see the opposite end of the spectrum--the area associated with low oil and cylinder wall temps. I was amazed at how much I could change the oil temperature in my old Corvette just by changing the load and rpm. The difference between 160 and 180 is minimal, but with carbureted cars, especially ones using aluminum manifolds with blocked heat crossovers, need all the heat they can get for proper fuel atomization and in some cases to burn the water/moisture from the oil. On a street car, I wouldn't run under 180. The extra hp or two just isn't worth the other problems that will surface.

[Z Code 400]

TransAm525,

I see your point, but even on street engines that have logged over 100,000, low rpm miles, sometimes with no thermostat at all, we would typically see around .004" to .006" wear in the cylinder wall, which completely disproves the .165" wear in 70,000 miles as indicated by the university's '50 hour test.'

You would be surprised to see some of the oil temperatures we have recorded with less than 170° coolant temperature...Robert

[steveopolus]

It is quite simple:

More timing, less fuel=Economy
Lower temperature allows more timing+ smaller jetting=Economy


580HP 467ci (455 bored .060, not a stroked 400) block hard filled to bottom of freeze plugs. 870 street avenger. 76 front, 82 back. 17 initial 38 total, all in by 2900.

160 T-stat, dual fan, be cool. Runs 165 all day long. 170 on the hwy at 75mph with the air on. 14mpg hwy. Sure I could squeeze another 2-3 more MPG with a vacuum advance to increase cruising timing, but for a whole bunch of other reasons I choose not too.

No crossover, no heat tube, 1" spacer (to keep carb cooler, not hotter) A carb only needs to be about 140 to 150 degrees for proper atomization. Anything hotter actually starts to pick away at its effieciency (totally different subject)

From cold 60degrees (about the coldest it gets here) 2 pumps, fires right up, feather throttle for 20 seconds and away it goes. No bucking, hesitating, needing to (warm up)
You would almost swear it was injected

Its about proper combination, the build, and tuning


And there is no comparison between a modern engine and an old Injun. Todays engines are designed by rocket scientists with all the exotic metals and computers at their disposal. The old Injun was designed by a nerd with tape on his glasses, paper, pencil, slide rule and cast iron.