Thermostat temperatures

[manifold]

Not being too anal I hope I spent an afternoon this weekend comparing so called equally marked thermostats I had in a box.

I noticed the 7 port was running 12-15 degrees warmer than the 5 port was and I was trying to work out why this could be. Maybe its because the 2 carbs take up more engine bay room causing less air to circulate? Maybe its because the head is more powerful, more power = more heat and all that... I would expect a few degrees difference for these reasons, but not so much as 15 degrees, even though it was running at an acceptable average max rate.

Anyway, cut to the chase it occurred to me that the thermostat might be off, as I used a brand new one in the 7 port (naturally).... so with this in mind I took the older thermostat off the 5 port and put it in the 7 port, observed that it was marked up the same temperature.....and guess what! average engine temps dropped by 10 degrees.

After testing a few thermostats, all marked to the same degrees they all opened up and closed at different temps.

So something for you to bear in mind if your trying to work out why your engine seems to be running hot. Check the thermostat by dangling it in a pan of water and properly check it out with a thermometer.

Cheers,

David

[Stuart]

So what were the temps?

I was under the impression that once open the engine temp would be the same? does that mean one of yours was remaining closed?

[manifold]

Ahh, well thats the thing. I thought the same as you too.

All of them opened and closed, but it was the speed of closure and the temperature of closure.

If you think about it. If one opens and closes at a higher temp, then it holds temp at the higher rate, meaning it starts to thermally creep from a higher point while at a standpoint. Like a hot day and stuck in traffic.

the 5 port one was holding at 74-80 degrees

the (initial) 7 port one was holding at 88-93 degrees. Now (when swapped) holding at 77-84. 86 at standstill.