Thermostats look similar but are different

[Cattrax]

My first start up created an over heating issue. I blamed the thermostat and bought a new one. Since the hoses to the front are long and water returning from the heater core is what opens the thermostat, I was going to drill a small hole in the divider plate to let some water flow directly from the engine into the thermostat area to activate it. I just had an "ah ha" moment. I was contemplating what size hole to drill in the thermostat to let water through when I noticed that the new thermostat (on right) was made differently. It has a hollow sleeve that is loosely fitted over the operating mechanism. This will direct a little hot water right over the plunger! The old one on the left does not. If you are having overheating at idle, you might try finding one of the thermostats shown on the right. I can get the NAPA number if anyone is interested.

I can't get a pic to download and need to run, later. Anyone let me know if interested.

Ken

[Cattrax]

tstat2.jpg
I tried resizing the photo.

[Cattrax]

tried resizing again.tstat3.jpg

[Cattrax]

Okay, that worked. The one on the right lets a little engine temp water through but the one on the left does not. NAPA part no. is 400186. Also on box was XXT-NA14298. Counterman said it was 186 degree t-stat.

[Edgeman]

I think that was the same one I used and never had a problem.

[crash]

Again, this is what the heater bypass valve kit that My Race Shop sells addresses. As the LS engine is designed, water must flow through the heater ports at all times. This gets hot water to both sides of the thermostat. The FFR supplied heater control valve simply shuts off the flow and causes a scenario where a cold start and idle will cause an overheat condition. Combined with an ineffective header tank location, again as provided by FFR, and you have a recipe for engine melt down. Get a proper header tank in the car, and make sure that there is flow through the heater core lines at all times and you will have no issues.

Your bypass thermostat is also a good solution for part of the problem in the cooling system, but you really need to look at a proper header tank as well.

BTW, neither of those thermostats looks like the later model LS thermostats. The later model ones do not mount into ears and the ones I have seen have a bypass hole drilled into the outer flange, which would do the same thing as the tube on the ones you show here. Always mount the newer thermostats with the bypass hole on top.

[Cattrax]

Crash, thanks for the info on the t-stats. I just looked for an LS t-stat that looked like my old one and was from a donor period Vette. I did see some with holes but either they did not have housings or the housing was oriented wrong. Since my old housing had ears I matched it, not knowing what else would work.

BTW, your header tank and supplied fittings look like they will fit and work great for venting the air. I am working on hose routing. The previous builder appeared to have directly connected the vent from the cylinder heads to the vent at the top of the radiator. Not sure how that was supposed to work. On my C4, they both connect to the fill tank to let air escape.

Ken

[crash]

Yes, the biggest issue is that the expansion/header tank that is used by FFR is below the level of the head steam vents. This will not allow the steam to move away from the heads. What is needed is to place a header tank above the head steam vents so that air can collect in the tank and not the heads. My Race Shop sells a complete kit for doing this, but in actuality, if you want to spend less and work harder, then you can achieve the same results by piecing things together. The MRS solution is offered for the convenience that all the required components are there in the kit. http://www.myraceshop.com/Header_Tank.html

[Cattrax]

All,
Here is a pic of Crash's tank installed. Install went well once I found a hose at NAPA with a 90 molded at the end (for water pump). I mounted it high, very little bleeding was required. 0831152237a (2).jpg
Ken

[Cattrax]

I don't have gauges but was able to Bluetooth my phone to an OBDLink. Started it up and let it idle. Temp went up to 190 and leveled off. New thermostat and MRS header tank did the trick.
Ken

[Cattrax]

Warm up and a few pulls on the dyno with no overheating! Previous owner had wrong MAP sensor and signal from MAF sensor was too noisy for accurate timing and fuel thus no glory pulls. That is fodder for a later post. Again, tank from Crash and new T-stat did the trick.
Ken