the design is to allow the heads to warm up evenly . this is to prevent them from cracking due to the thin walls in the water jackets.
the block off plate has cured many pantera hot running probs in spite of the poor design of the rest of the cooling system.
the brass colored thermostat you have also looks like a high flow one and just using a high flow thermostat has helped reduce temps in many cases so its not possible to contribute a hot running cure to the machined brass parts alone.
Yes, it is the high flow Robertshaw thermostat that the Ebay seller (the machinist) adds his machined skirt to. This high flow design with the skirt is how the Cleveland's cooling system was originally equipped. The others, although they are quite cheaper, are not as refined and it was important to me to have the skirt, of the thermostat, flawlessly mesh with the orifice in the brass bypass washer. When you want something to mesh flawlessly, you go to a machinist AND pay him to do it right.(he's already done it) ***THESE PARTS WILL NOT "CURE"^ HOT RUNNING PROBLEMS IN ALL CLEVELANDS. :shootself: THEY MAY WORK BETTER THAN CRAPPY PARTS THAT MAY NOT MESH TOGETHER WELL***
Personally, I have done everything I could in planning and building my engine to assure no overheating. In fact, last summer I was in 2 cruise nights, 95°+ temps on the road, sitting in traffic (parade of hot rods), with my windows up, Classic Auto Air blasting (it was literally cold), for over 2 hours and my temp never rose above 180°. 3 core brass radiator and dual Spal fans with a Painless controller. I too, was amazed.
http://www.amazon.com/Spal-30102130-Dual-Extreme-Performance/dp/B003PB9S8G?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o06_s00
http://www.amazon.com/Painless-30140-Dual-Fan-Controller/dp/B003XLE2LQ/ref=sr_1_1?s=automotive&ie=UTF8&qid=1458907253&sr=1-1&keywords=painless+30140
Well worth it.
So, maintaining bypass is part of a system (that needs to be understood) and may not "cure" an overheating problem but you start by doing all the little things right and you'll end up with a more dependable machine. ***Yes, an electric fan can malfunction...but so can a fan belt or a water pump belt. :shootself: ***
This "brass bypass washer" subject has mucho content on this site written about it. There are strong opinions. People like to defend their point of view. All I'm saying is you'll have a better chance of it working as the engineers intended to, if your parts work
together nicely. Get good parts. Pay the $125 for the good washer and thermostat and know you made the best choice for your beloved engine...a small price to pay.
If any of you want the Aluminum Pantera blocker plate, I have a brand new one, in the box, from WCCC (who did not invent/make it-they only sell it AND none of the WCCC guys use it in their Clevelands), that I won't be using.
Our purpose here is to help others gleen information and make decisions as to how to proceed in their builds. My only intent, is to help, as many here have helped me.
Read everything you can and never just listen to one person's opinion. Discern the truth from all the information you gather and proceed how you see fit. (to me that's where the fun is, you get to chose for yourself) Good luck on your builds, keep the passion and do it right or don't waste your time.
By the way,
respectfully, your last sentence would make more sense with the word "attribute" as opposed to the word "contribute."