On Mon, 28 Jan 2013 02:53:26 -0600, wrote:

On Sun, 27 Jan 2013 13:50:16 -0500, wrote:

On Sun, 27 Jan 2013 13:45:45 +0000 (UTC), Tegger
wrote:

wrote in news:a949g8p7fatqaffk23cq48p5vnfoqn6q7v@
4ax.com:


2 minutes would likely be safe. 5 would definitely be pushing your
luck.




Even 30-seconds is not safe if there is no coolant in the head. The rad
being missing is NOT the same as simply having low coolant-level in a
complete system.

Combustion temperatures are around 1,500-2,000 degrees F. That heat builds
in seconds if it can't be carried away; without coolant, the surrounding
metal will overheat /very/ quickly, creating the strong probability of the
head warping, which will cause head-gasket failure and poor valve sealing.


Are you a mechanic???
I am. 30 seconds will not hurt ANYTHING. Period. The thermal mass is
highe enough to take a minute of no or light load running without harm
- even on a lightweight aluminum engine. - in most cases significantly
longer.

The Ccadillac Northstar can be driven 50 miles with absolutely no
coolant, without harm - and it is a FRAGILE engine. They do it by
rotating shutdown of cyls and reducing power output.

I would not run a dry engine for 5 minutes - but I have posted a
solution that works very well and is totally safe for a 5 minute run.
- short circuit pipe..

That's the Cadillac engine I mentioned in another post.

This whole thing does have me asking how it is that air cooled engines
survive as long as they do? Particularly the larger ones on garden
tractors, skid steers, etc?

How about aircraft????

Yea, I know they have cooling fins, but hey, people use them all the
time when the outdoor summer temperature is in the 90s, and the air is
still. Often they are just sitting at idle. How can they be getting
cooled properly? Yet they seem to last a long time in most cases. Those
find cant be doing much when there is no air movement, and usually no
fan either....

Are they built from stronger metals than a car engine?
Nope - usually crappy aluminum aloys