Last months Chevy High Performance listed a response to letter in which they talked about buying an engine that has never seen over 3000 RPM and rarely come fully up to operating temperature having considerable wear to the cylinder wall. The motor is then mildly modified and driven with more enthusiasm at which point the top ring is bashing up against a ridge that it has created and all hell breaks loose.

My question is; how does engine temperature factor in. I ask because I have been running with a temporary fan switch setup all summer that keeps the engine operating at only about 1/4 on the gauge. Thanks,
Jon

JSD MOD 20/07/08

 

Your pistons won't grow fully, and rings won't heat up and push out against the cylinder wall. It has more to do with the oil never getting up to temp, and not properly lubricating the engine though, i'd imagine.
Put a thermostat in your car and run it at operating temperature.

 

It's not so much the coolant temp as it is the oil temp. The oil picks up moisture and all kinds of contaminants. Water vapor is one (which boils off when the oil reaches temp and stays there for a while) but there is also all kinds of carbon and sludge from cold-engine combustion (which can gum stuff up and doesn't go away unless you change the oil often). Plus, cold oil doesn't always get where it's needed right away because it's thick and doesn't like to flow or get thrown around very well by the various moving parts of the engine.

Add it all up and you can get very accelerated wear at various places around the engine, including the rings/bore.

The original 305 engine in my 78 Malibu had only 33K factory-original miles on it when I inherited the car. Amost all of it short trips to the grocery store and church (grandmother's car). The inside of the engine was a disaster area when I pulled it apart. Sludge 1/4" thick in the lifter valley. Rust showing on various parts that weren't covered with sludge. Plenty of bore wear with a nice ridge at the top, lifters were so gunked up I'm surprised they worked at all. It looked like it had a million miles on it. Likewise, the engine rarely saw the high side of 3000 RPMs.

Cold oil is not your friend.

You can run a 160* stat and never have a problem if you don't do a lot of short trips. It's getting the WHOLE engine (including the oil) up to temp and keeping it there for a while that makes the biggest difference. And it takes a lot longer to get the oil up to temp than it does the cooling system.

 

OK so I'll have to deal with this ASAP. For various reasons, I had to ditch the stock fan switch and I am using one that runs off a probe in the rad. There is a more expensive version that alows the user to select the on/off temp. Currently the fan comes on too early and stays on too long.

Thanks for this crucial advice!
Jon