For initial break in tomorrow I have straight water in it. I'm a little worried about it running hot so I'm planning on running it without a thermostat for the break-in, just in case it malfunctions for some reason. Is this a good idea?

I run a 160 F degree H.D. thermostat in my pump gas motor, I did drill 3 1/8 inch holes in the outer flange to allow the air to escape, if it gets to hot on the cam breakin time shut it off and let it cool down for ten to twenty minutes with the box fans on the radiator and then run it some more. You can remove it and reinstall it later, your call

Thermostat in, test it beforehand on the stove.

as soon as you get it started get the timing light on it and bring the advance timing to 35 degrees , as said get a box fan in front of the rad to get air flowing thru it.

The timing not being advanced enough is the biggest reason for an engine to overheat of came break in .

Id leave the thermostat out. Its one less thing to be concerned about during that busy startup time. Your watching oil pressure. fuel lines oil leaks ect... A friend of mine recommended this when he had one fail. Water went everywhere scallding that fresh paint and it was a black car.

Engines are designed to be at operating temperature not less than operating temperature. I always run a 195 t-stat and watch the gauge. I don't think it's a good idea to try a fresh startup on something other than a stock rebuild by yourself either. It's good to have someone in the driver's seat watching the gauges and ready to shut it off while you check over and watch everything going on under the hood.

Sheldon

Its liable to run hotter without the T state because there is nothing to restrict the flow through the rad giving it a chance to cool properly.. Put the stat in !

A thermostat will not cause n engine to heat unless it is faulty. 160 is too cold. Better lubrication with a hot stat.

I vote for using a good 180' stat like a stainless NAPA superstat and drilling at least one 1/8 inch hole between the rim and the stat "motor" for air bleed.
Testing on the stove is an EXCELLENT idea (wish I thought of it)
The stat gets the motor up to temp quick and stabilizes temp for break in, which the motor WANTS!
All the stuff we have is designed to run at 180' for clearances, oiling, metallurgy etc.

I would use a thermostat for sure, Why not?

They are reliable and I would use a 195 stat.

I don't think I have ever had a bad one and I have installed plenty when I replace anti freeze.

I wish I used a NEW 'fail-safe' thermostat with the above mentioned 1/8" air purge holes on my new startup. What happened is that the thermostat either got stuck, or there was some air trapped underneath because with the rad pressure cap off (I kept it off to make sure coolant was circulating properly, etc, etc...may not have been the smartest thing to do in hindsight) all of a sudden I got a huge geiser shoot up!!! Nasty nasty...what a mess...not the sort of a thing you want to encounter during a fresh engine startup...certainly not after months and months of work to put the combo together, get it into the car, etc, etc...ahh...lessons learned!

I can't think of any good reason not to run a stat. These engines are made to be run at a certain operating temp.

whether you have a thermostat in or not..

Just have the hose with a sprayer available to hose the radiator down if it starts to run hot..

I like to run them outside, if possible, to get fresh air around the engine to take away the paint fumes, spilled oil fumes, etc. If you can point the car into a nice breeze, this will help.

The problem is gettin water in the block with no air. You should use a high flow (robertshaw)190-195 with a few 1/8 holes to bleed the air out. I also use a fill funnel on start ups to get the block and rad full of water and bleed the air out. Proper advance timming also helps alot to keep the heat down. I also use two fans in front of the rad to keep the heat down. Good luck.

Thanks for the help guys. It all went very well. The cam break in went perfectly! It started right up after cranking a few times and immediately ran it up to 1800-2200rpm and kept it there, varying it up and down for about 30 minutes (that was a LONG 30 minutes!). I was shocked how smooth it ran immediately and didn't skip a beat the whole time. I set the total timing at about 34* and initial is 10-12*. I ran it with straight water and no thermostat. I also had a box fan blowing into the grill. The temp stayed very cool for about the first 15 minutes, then it slowly creeped up to 195, almost 200. At that point I misted the rad with a garden hose and that brought it right down. The oil pressure stayed at 50 cold and 45 hot.

I let it cool, pulled all the spark plugs and they looked real good. Then changed the oil and filter, double checked everything and ran it a little more...idle, mid-range, blipping. It seems very responsive and sounds great out of the exhaust.

The amazing thing is that there are NO leaks at all! Even the valve covers were dry! Amazing!

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whether you have a thermostat in or not..

Just have the hose with a sprayer available to hose the radiator down if it starts to run hot..

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The hose trick worked well. I'll have to see how it runs on the first road test Friday. Hopefully it will stay cool.

you did everything right & it went well. Even you're your initial/total looks good