# no thermostat break in?



## tjs72goat (Jul 20, 2017)

Would it be fine to break a new motor and cam in on a test stand without the thermostat in place?


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## PontiacJim (Dec 29, 2012)

Good question. As long as you have a temp gauge hooked up on your test stand and can monitor the water temp so you can shut it down if it overheats, suppose it would be OK. 

But for $5 bucks(?), why would you not install it and not have to worry - you are scarring me. Don't ask me if its OK to run the engine with extra oil in the pan and no oil filter 'cause then I will be scared.

So honestly, not sure. Might help to ensure no trapped air in the system or heads and create a hot spot.


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## BearGFR (Aug 25, 2008)

The 'no trapped air' idea is a good one. I address that problem myself by drilling a very small hole (1/8" or less) in my thermostats to create a small "bypass" that lets air escape so I get the cooling system full even on a cold engine. The first startup happens with the radiator cap off so I can top things off when the pump starts to move coolant. Air can get trapped in the heater hose that connects to the head (or heads in my case - I connect coolant hoses to both heads and T them) if it's higher than the thermostat. 

Bear


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## 64GTOConvertible (Aug 28, 2016)

OK, so a t-stat will prevent water from circulating until the engine warms up. What happens when you have no t-stat? 2 things. 

1. The engine will not get up to operating temperature.

or

2. The engine will overheat as the water flows through the radiator too fast to allow cooling. 

You won't know which will happen with a new engine. What I would recommend is take the guts out of an old t-stat if you want to run without. But I don't know why you would go through all this trouble. Put in a new t-stat.


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## tjs72goat (Jul 20, 2017)

The guy I work with (engineer) who built the short block and heads, mentioned the no thermostat. I have been slowly finishing the rest of the bolt on components. He builds many engines and also drag races high end cars. I mentioned to him the thermostat and filling with water and air pockets. He said without the thermostat, the fill will allow the air pockets to come out and not be a problem. Once the cam is broke in on the stand, the thermostat will be installed and ready to put in car. I guess I never heard of running without a thermostat either, but I don't have much experience breaking in a new motor either.


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## PontiacJim (Dec 29, 2012)

tjs72goat said:


> The guy I work with (engineer) who built the short block and heads, mentioned the no thermostat. I have been slowly finishing the rest of the bolt on components. He builds many engines and also drag races high end cars. I mentioned to him the thermostat and filling with water and air pockets. He said without the thermostat, the fill will allow the air pockets to come out and not be a problem. Once the cam is broke in on the stand, the thermostat will be installed and ready to put in car. I guess I never heard of running without a thermostat either, but I don't have much experience breaking in a new motor either.


Makes sense, but it seems each person has their own opinion on this even when checking other blogs. It was mentioned that without the t-stat that the temps may slowly climb up around 200 degrees - as your cooling system will only be as good as your radiator. A new engine will usually run on the hotter side because it is "tight." So it is recommended to keep a garden hose ready and watch the temp gauge and if it climbs a bit too high, then hose down the radiator to cool things down OR some use additional box fans in front of the radiator for extra air flow.

I drill 3 evenly spaced 1/8" holes in the outer rim of the t-stat which will also allow trapped air to escape. One blog mentioned he ran his engine at a slight tilt with the front upward slightly to aide in the trapped air to escape.

So I guess this one is your call. Maybe invite your engineer buddy over for some grilling and the first firing of your engine so he can be there to help. A good cook-out just can't be turned down. :thumbsup:

Make sure your timing is correct. If it is retarded too much, temps will rise very quickly.


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## tjs72goat (Jul 20, 2017)

I plan to run this at work on another co-workers test stand. So, the engineer who built the short block will be there to take the lead on the break in. He has way more experience on new engines than I do.


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## PontiacJim (Dec 29, 2012)

tjs72goat said:


> I plan to run this at work on another co-workers test stand. So, the engineer who built the short block will be there to take the lead on the break in. He has way more experience on new engines than I do.


Perfect, then go for it and let us know how it turns out as I am curious myself.


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## tjs72goat (Jul 20, 2017)

I asked his son who is also an engineer and just started working for us about six months ago. He said they run new engines without thermostats all the time on new break ins and they actually run cooler. That's why they do it.


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