Ok, then easy fix with a die grinder. Put a slot in the housing under the stat.

Right where I drilled the hole.

 

I would be willing to bet you still have a air pocket in there a very common on first fire up jack up the front of the car up so the radiator cap is the highest point of the car and while the car is running and the thermostat opens,cap off the radiator and use a shop vacuum and cup your hand around the neck and the vac.controling the amount of vacuum with your hand suck the access air out of the system NOT the coolant and you will be golden.

 

I will crack the front two coolant crossover plugs while the car is running to get the air out. I had this exact issue, and it got all the air out the system and the car stopped overheating.

This was after I did head gaskets on the car.

 

Before you built this engine did the old combo run cool or normal? What on the cooling system changed? If nothing then that means the engine is creating more heat... why would it? Ive seen clearances too tight do this... but that would be evident in the oil (sparkly). Before putting any money into the cooling system if it worked fine before I would add a little more fuel and adjust the timing. Timing could also make it run hot at idle and cruise.

 

mine still gets hot when driving, althought I've only put <5 miles on it

HG's are on right. back of the heads are getting water

I do see what you mean here and makes sense. is the thermostat activated by the part of the tstat that seats in the inner most part of the pump, or the WP inlet side from the heater core? strange thing though, I've seen numerous people on here that have plugged these ports without issue, although i'm not sure if they eliminated the tstat or gutted them to allow more flow.

running a stock sized C5 balancer

will give this a shot

very interesting comparisons Ron. i'll pull mine apart and take a look

I did get coolant out of the ports, but did not leave them open when the motor was running

Very interesting mod. sure beats having to tap/weld new fittings to the pump

will try this as well. Thanks

Don't know. it was a junkyard motor that I torn apart right away, so I never knew how it ran before. oil looks good with no metal particles after 2 oil changes. i'll look at my tune to see how the timing looks around idle, I didn't think about this.

 

I was finally able to tear it apart and snap a few pics.

modified CSR housing


bypass end of 160* mr gasket stat


stat sitting flushing in CSR housing


approx. 1/4" compression of bypass valve into WP housing


stat view through CSR housing inlet


plugged heater ports


steam vent fitting into WP outlet


I've also modified the pump as RonSSNova posted and will give this a try. I have everything put back together but haven't had time to test it again. Hopefully this weekend i'll have some feedback.

 

I know you have it back together. One thing I notice from the pics is the height the therm sticks out of the WP housing. Mine is more like 1/8". Would have been interesting to compare that therm height with the stock one.
Let us know how it works.

 

One thing i didn't see asked is if your radiator cap the highest point in the system?

Also food for thought; With the cap off water will boil at 212 at atmospheric pressure, add 20 pounds to that with the cap on and it will boil at 258 or so.

 

Well guys I have some good news. I have the car all back together and took a for a drive earlier today. With the mod done to the WP as RonSSNova suggested, newly burped coolant system, and only 1 pusher fan (mounting hardware zip tie things broke and couldn't mount the other one up), the motor ran around 205 while cruising and maxxed at 225 when sitting at a light but pretty sure the other fan would have helped here.

i'll get the other fan mounted up and see how it helps. I feel a lot better about it now and have a better place to start for when I can start driving it around more regularly.

Thanks for everyone's help and suggestions

 

^^^^^ What Ron said. That's a 160 stat. No reason it should be running 205.

 

Hey, good news. Huge improvement from where you were.
Which temp sensor are you reading?
What was the air temp outside?

As far as it running at thermostat temp. It will only do that if the entire cooling system can support it. Radiator size and airflow.
The vette guys have this argument all the time. Blah blah blah...:-). They will also argue that anything other than the stock 197 deg unit will ruin the engine.

I do think that mr gasket thermo fits odd. The 160 I bought is from SLP and fit like the stocker.

It will be awhile before mine runs. The radiator I have cooled the rat motor almost too well.

Ron

 

So that modification to the water pump is just basically making a point where water can bypass the thermostat a little more correct?

 

Much better, Thanks!

i'm reading the temp sensor in the driver's head.

It was a nice day out when I drove, I don't recall exactly but I think it was in the mid 60's.


Yeah, it basically acts like the looped heater ports to allow for additional flow.

 

Ok so if you have a heater in the loop it is pretty much a useless mod?

 

Correct. The OP has the heater ports blocked.
This is not a proven mod. But if the "heater ports need to be looped" this will accomplish the same.

Ron

 

Ah ok. Going through something similar with my build, but I have a heater core. So I suppose this would not help.

 

I had to run a dual pass rad before I stoped having issues. Also is your hoses correctly routed.

 

Dual pass rad and hoses are routed correctly. Thinking it has to be an air pocket.