Technical Chevy 261 cooling

I've a small problem when first running this 261,it gets quite a bit hotter than 180 on the water temp ga,then the thermostat opens and then it cools back down to 178/180 and runs fine from there on, it just does this on first start of the day,today it went to 220 before it opened and the cheap ass gauge stuck there, when I put this engine together I used the early 235 water pump and adapter plate to put the fan back where it was with the 235 and I used the 235 thermostat housing, the 261 water pump had 2 fittings on it 1 for the heater and I'm guessing the other for a bypass, the 235 pump has just one fitting on it,that would be for the heater, now my guess is that the thermostat is taking quite a bit longer to heat up to open, the 261 stat housing has a fitting above and one below the thermostat,could I run a hose between those and keep the engine water circulating to heat up the thermostat quicker,I had not used the 261 housing because it was quite a bit bigger and I may have to make new fuel pump lines when I do put it on, but it has the fittings as the 235 housing does not,also it uses the bigger thermostat. Has anyone had this problem.
Thanks Aaron

 

i wonder if you drill a very small hole in the thermostat to allow a little flow?

 

My 250 was doing this. It would develop an air pocket in the system while cooling. When the motor would cool it would suck all the coolant from the catch can and then suck a little air. Every time I started it after sitting it would get hot until the thermostat opened and blew the bubble out. I just kept adding a little more fluid in the catch can until when it was cold it still had some in it.

 

Replace the thermostat.

 

Are you running a 235 head? If so did you drill the steam holes? I had the exact same problem and drilling a small hole in the thermostat did solve it, but subsequently I realized I hadn't drilled the steam holes in the 235 head I used. Haven't run it since drilling the steam holes so I don't know if they will have an effect on that issue but just thowing it out there.

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I'm going to check the stat and see if it has the bypass hole in it,if not I may put in about an 1/8" hole and try that.
The stat works the rest of the time after the first opening,maybe it does develop an air pocket when sitting over night,the bypass hole might clear that up.
Yes this is the 261 head with the steam holes,I kept the 235 head off the old engine as a spare knowing that I'd have to drill those if I used it, also I was thinking I could use the 235 stat housing as it does have a fitting on the bottom half and run a 3/8 bypass line to the water pump heater fitting to circulate water, from what pictures I could find it looks like that was what was done on the 261's, but the bypass hole in the stat is where I'll start.

Thanks

 

My 250 has the bypass hose and a small hole in the thermostat. I was still developing the air pocket because my top radiator hose is about level with the fill cap. Once it got to pressure, it would burp the air out.