CHT Temp, What is the upper operating limit? Options

[ericread]

Based on the converstaions here,I drove over to Corona, CA (Aircraft Spruce) this afternoon and purchased the Micro 1000 CHT, a sensor and a 15 foot extension cable. It's all installed and looks great in my original center console.

So where is the danger point? Some posts say that hitting 400 degrees will cause a valve seat to fail. Others say they regularly see 375 to 400 degrees on their longer, higher speed drives. Where is the point that indicated engine heat danger? BTW: 74 2.0L all original FI w, standard exhaust.

My thanks.

Eric Read


NOTE: Please note that this was originally posted in a CHT topic post. After about a day, I received no responses, so I am re-posting it as a unique topic.

Cross-Posting Disclosure: Cross-posted to the "other" BBS (Saturday, 10/11/08) as a result of no response on this BBS.

[toon1]

If you take a head and put it in the oven with the chamber facing down...then heat the head to 400 degrees and let it sit like that for 20 minutes....you may see the valve seats come loose.

that is the tolerance for these heads so if you are running temps that high, your timing may be off, you may need different oil, you may want better plugs, your cooling tin may not be attached correctly/leaking/missing parts...
Your engine may also be filthy underneath the head tin...

Rich

This is true. I don't like seeing temps that high.

But there is one factor that might come into play, the cumbustion chamber temps are very high changing the expansion rate of the valve seat.

When I saw temps that high, the engine had 1500miles on it, timing was about 25* and AFR was 13.5:1.

The biggest factor was , I was pulling a long hill on a warm day(85*) into a good head wind.

I was definetly not comfortable with 407*. I pulled the same hill again in different conditions and the temps where about 385*.