[DeTomaso] Interesting Robertshaw 333-180 thermostat design change

B Hower b.hower3400 at yahoo.com
Sat Nov 16 23:47:24 EST 2019


Dear Mike,
What do you say happens, if one uses a Windsor style thermostat ( no hat, full flow style as the true Robertshaw 330-180 ) and the OEM disc?

I am sure this has come up in the past, but I need a refresher course.

Please help,

Bud #3400 ( Drive it like there is no tomorrow -- for there may not be ! ) 

 

    On Saturday, November 16, 2019, 10:04:00 PM CST, Mike Drew via DeTomaso <detomaso at server.detomasolist.com> wrote:  
 
 All,

The Robertshaw 333-180 is the ultimate thermostat for the 351C—or at least it used to be. 

There has been an undocumented design change with the same part number. Now, instead of supplying a thermostat with the 351C ‘hat’ which partially (but not fully) blocks off the orifice in the center of a disc pressed into the block, instead they are supplying a conventional Windsor thermostat (ordinarily bad news) along with a replacement disc with a smaller (too-small) orifice. In order to use this thermostat the stock disc needs to be removed from the block and replaced with this new one. That then means that going forward only NON-Cleveland thermostats can be used. If a proper 351C thermostat is installed, it will be prevented from fully opening because the hat will strike the now-too-small disc.

With this new setup, when the thermostat opens it will fully block off the orifice. However, the engine is supposed to have at least some water circulating past the disc, with an area equivalent to that of of a 5/16ths bypass hose as used in other Ford engines. (If you compare the size of the stock ‘hat’ with the hole in the stock disc, you will see the hole is measurably larger). If I was to use this new setup, I would therefore be inclined to modify the disc, either by drilling bypass holes or (preferably) enlarging the center hole.

Too, the stock setup allows for some misalignment between thermostat and disc. If the thermostat wasn’t perfectly centered, it would still have room to fully open. With this new deal, if things aren’t perfectly aligned, it might not fully open, or worse, it might open and get stuck open, leading to very slow warmup problems. 

Here is a pic of a ‘real’ Robertshaw 333-180 compared to the new one:


Here is the new one with its included disc:



And the disc laid over the thermostat:



I’m sorry I don’t have a stock disc handy to compare, and show the clearance between the orifice and the hat. You will just have to take my word for it....

Mike (hoarding his one remaining good thermostat!)

Sent from my iPad_______________________________________________


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-------------- next part --------------
   Dear Mike,
   What do you say happens, if one uses a Windsor style thermostat ( no
   hat, full flow style as the true Robertshaw 330-180 ) and the OEM disc?
   I am sure this has come up in the past, but I need a refresher course.
   Please help,
   Bud #3400 ( Drive it like there is no tomorrow -- for there may not be
   ! )

   On Saturday, November 16, 2019, 10:04:00 PM CST, Mike Drew via DeTomaso
   <detomaso at server.detomasolist.com> wrote:
   All,
   The Robertshaw 333-180 is the ultimate thermostat for the 351Caor at
   least it used to be.
   There has been an undocumented design change with the same part number.
   Now, instead of supplying a thermostat with the 351C ahata which
   partially (but not fully) blocks off the orifice in the center of a
   disc pressed into the block, instead they are supplying a conventional
   Windsor thermostat (ordinarily bad news) along with a replacement disc
   with a smaller (too-small) orifice. In order to use this thermostat the
   stock disc needs to be removed from the block and replaced with this
   new one. That then means that going forward only NON-Cleveland
   thermostats can be used. If a proper 351C thermostat is installed, it
   will be prevented from fully opening because the hat will strike the
   now-too-small disc.
   With this new setup, when the thermostat opens it will fully block off
   the orifice. However, the engine is supposed to have at least some
   water circulating past the disc, with an area equivalent to that of of
   a 5/16ths bypass hose as used in other Ford engines. (If you compare
   the size of the stock ahata with the hole in the stock disc, you will
   see the hole is measurably larger). If I was to use this new setup, I
   would therefore be inclined to modify the disc, either by drilling
   bypass holes or (preferably) enlarging the center hole.
   Too, the stock setup allows for some misalignment between thermostat
   and disc. If the thermostat wasnat perfectly centered, it would still
   have room to fully open. With this new deal, if things arenat perfectly
   aligned, it might not fully open, or worse, it might open and get stuck
   open, leading to very slow warmup problems.
   Here is a pic of a areala Robertshaw 333-180 compared to the new one:
   Here is the new one with its included disc:
   And the disc laid over the thermostat:
   Iam sorry I donat have a stock disc handy to compare, and show the
   clearance between the orifice and the hat. You will just have to take
   my word for it....
   Mike (hoarding his one remaining good thermostat!)
   Sent from my iPad_______________________________________________
   Detomaso Email List is not managed by POCA
   Posted emails must not exceed 1.5 Megabytes
   DeTomaso mailing list
   [1]DeTomaso at server.detomasolist.com
   [2]http://server.detomasolist.com/mailman/listinfo/detomaso
   To manage your subscription (change email address, unsubscribe, etc.)
   use the links above.
   Members who post to this list grant license to the list to forward any
   message posted here to all past, current, or future members of the
   list. They also grant the list owner permission to maintain an archive
   or approve the archiving of list messages.

References

   1. mailto:DeTomaso at server.detomasolist.com
   2. http://server.detomasolist.com/mailman/listinfo/detomaso
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