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Topic ClosedINFO: Thermostat for 351 Cleveland, 351M or 400

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Anderslober View Drop Down
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Direct Link To This Post Topic: INFO: Thermostat for 351 Cleveland, 351M or 400
    Posted: 30-August-2019 at 7:19PM
Hello Forum.....do 351 clevelands/cj`s use `special` thermostats?

Which thermostat will do? Robertshaw333 high flow......?Tridon High flow? Others...?

Any info is good....thanks....
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Direct Link To This Post Posted: 31-August-2019 at 12:58AM
The 351C needs a thermostat with the little "hat" at the bottom to block the bypass.  Often times retailers will list a 351W one for a 351C.  You can look up a thermostat for a 1972 400 and it will usually be correct.
 
 
Or better yet, get a highflow one from Tim Meyer:
 
Vince

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Direct Link To This Post Posted: 31-August-2019 at 1:11AM
Those 2 examples look very different. Both work..? 
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Direct Link To This Post Posted: 31-August-2019 at 1:13AM
Yes, the bottom one is a high flow which is why it looks so different. But it is also much more expensive.
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Direct Link To This Post Posted: 31-August-2019 at 5:18AM
i've heard the 'hat' can be removed from a correct thermo and installed onto a Windsor, generic / chevy style thermo and it becomes the Robertshaw 333 series. the only difference between the Windsor and Cleveland thermos from Robertshaw was the presence of the bypass restrictor hat installed onto the temp sensor bulb. other than that the 2 thermos are identical. supposedly the tooling for making the hats was worn out or damaged and Tim Meyer www.tmeyerinc.com bought the tooling, had it repaired and is having some outfit producing correct 333 style thermos available new in the box (NIB) but out of stock for the near & distant future.

FWIW you can source correct thermos from Rockauto for under $5, search under 351 cubic inch and make sure you specify Q code for the VIN and look at the pic if it's available. this will get you the correct Cleveland specific thermo, i don't trust their listings for 400. example look at RT351, it doesn't have the hat yet they're spec'ing it for a 400 which also uses the same internal bypass system as the 351C. all the listings have been corrupted by data entry incompetents that knew nothing of the items they were uploading into the system when they went from actual paper books to computer. it'll never be right again Cry

custom made hats and restrictor plates are available from ebay seller neonfiddler but not cheap.



Edited by Rockatansky - 31-August-2019 at 5:28AM
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Direct Link To This Post Posted: 31-August-2019 at 3:17PM
Great info..thanks. Over on Rockauto...no `Q` code.....but `4BBL`.......same?
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Direct Link To This Post Posted: 31-August-2019 at 4:14PM
i forgot to mention Q code only 1971.5 - 1974, from 1970 - 1971.5 it was M code

i usually look up for 1972 to avoid the mid-year break but M code should be 351C specific and correct also


4bbl leaves open the possibility of getting a Windsor stat, there were some 351W-4V's

H code can be a Cleveland, Windsor or 351M depending upon model year, high likelyhood of  getting the wrong stat
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Direct Link To This Post Posted: 31-August-2019 at 8:03PM
Thanks...great!...found it now! In 73..no `Q` code....hehe....one has to be sharp and pay attention!
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Direct Link To This Post Posted: 01-September-2019 at 1:35PM
Originally posted by Rockatansky Rockatansky wrote:

FWIW you can source correct thermos from Rockauto for under $5, search under 351 cubic inch and make sure you specify Q code for the VIN and look at the pic if it's available. this will get you the correct Cleveland specific thermo, i don't trust their listings for 400. example look at RT351, it doesn't have the hat yet they're spec'ing it for a 400 which also uses the same internal bypass system as the 351C. all the listings have been corrupted by data entry incompetents that knew nothing of the items they were uploading into the system when they went from actual paper books to computer. it'll never be right again Cry
 
I missed that RT351, but most of the other thermostats appear to be correct.  I just figured the 400 listing would be easier than muddling through the 351 listings. But in guess you are right, the catalogs are all so messed up you can't rely on them.
 
Here is the info from Ford on the bypass:
 
 
More information at this link on using the proper bypass, see figure 1 and 2:

http://www.are.com.au/feat/techt/thermostat.htm


Here are a couple of pics on thermostats.
 
You can clearly see the brass hat on the Robert Shaw high flow style thermostat.
 
 
Below is a traditional style thermostat.  The brass hat is harder to see, but you can see it if you look at the bottom of the thermostat (the brass ring around the copper button in the center):
 
 
Below are some shots of an older one I have on my work bench, and you can see the "hat" at the bottom:
 
 
 
Below is a 351W style Thermostat - look closely to see the difference. Note the open area around the bottom brass button area in the center of the thermostat.  This will not block the coolant bypass because there is no hat to fit in the bypass hole.
 
 
I think the most important thing is that if you order a thermostat for a 351C/351M/400, you need to verify the hat is in place on the thermostat. Not all the Rock Auto photos show the bottom, but several do. Or if you pick up from a local parts store, just check it before you buy it.
 
For future reference, these ones are known to be correct:
 
  • Robert-Shaw 333-195:  This was a high-flow thermostat, now reproduced by TMeyer here.
  • Gates 33129
  • Napa 297
  • Stant 13469
  • CARQUEST 13469
  • Motorcraft RT-139:  This one is said to obsolete but they do turn up from time to time
  •  



    Edited by 72FordGTS - 14-March-2020 at 12:06PM
    Vince

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    Direct Link To This Post Posted: 01-September-2019 at 2:07PM
     what about the motorcraft RT 1167 last listing in that link it looks like the only one  that has a plate at the bottom? the rest dont, is that the area that needs blocked?
    JOHN
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    Direct Link To This Post Posted: 01-September-2019 at 3:13PM
    no telling where that freak belongs Confused

    from the listed applications i'd scratch it off the list most ricky ticky

    click on the highlighted part number


    --------------------------------

    there sure enough was a Q code in 73 and 74, that's what i mean about the listings being fubar'd,

    yeah we just have to be smarter than the confuser in front of us LOL

    here's a great explanation of how the system works


    IDK why sometimes my links work and sometimes they don't?


    Edited by 72FordGTS - 01-September-2019 at 3:35PM
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    Direct Link To This Post Posted: 02-September-2019 at 4:39AM
    a couple pics of the restrictor orifices

    this is the 351C pressed in brass insert, many times it's been removed by a machine shop or somebody trying to 'fix' an overheating problem.



    and the integral cast in 351M / 400 restrictor orifice, works the same way as the pressed in brass insert



    there are also aftermarket 'block-off' restrictor plates that have only a small air bleed hole that allow the use of a generic style stat. before installing one of these you should really make sure you understand how the system works and that there is a coolant flow path while the stat is closed or you'll create a condition that causes hot spots in the heads and risk gasket failure or worse.



    here's Tim Meyer's Trackboss restrictor plate, should retrofit into all factory blocks if you need a replacement



    one more time LOL, wrong on the left, right on the .....right




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    Direct Link To This Post Posted: 02-September-2019 at 5:21AM
    Fantastic! Amazing information! 
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    Direct Link To This Post Posted: 20-September-2019 at 6:08AM
    Well, this was a timely thread...

    I've had my car with the 351c for about a month and it didn't seem quite right despite having a large aftermarket radiator. So, while I had the coolant drained to replace the coolant temp sender for the gauge I checked the thermostat as well. Sure enough, no "hat":



    I replaced it with the Stant 13469 and the cooling system seems to be working much better now.

    Thanks to all who chimed in!
    Joe
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    Direct Link To This Post Posted: 06-December-2021 at 2:57AM
    [QUOTE=72FordGTS][QUOTE=Rockatansky]
     
     This is the only style thermostat that should be used. The other hat designs do not flow enough coolant when open and cause the coolant path to continue to circulate in the block. The shaw design addresses the flow issue with the huge top opening allowing coolant from the radiator top hose to easily be pulled into the block. Having the lower hat to block the plate is a must but the big issue with this block is flow. The shaw thermostat was in the car from ford. If you look at the top of the others you can see how small the opening is compared to the shaw design.

    The Robertshaw 330 series looks like the 333 series from the top, but flip it over & they're not the same. The 330 series is the universal thermostat that fits small block Fords, small block Chevys and small block Mopars.

    That's also one way to determine what Mr Gasket & others are selling ... search which motors the thermostat fits. The 333 series fits 351C, 351M and 400 only. And a thermostat that fits 289/302/351 Fords, small block Chevys or small block Mopars will not work properly in a Cleveland.

    Ford has used the Robertshaw high flow thermostat in many applications since the 1960s, and I believe they still use it today. They all look the same from the top, but only the one designed for the 351C has the little 11/16" flanged button on the bottom. Its a small subtle difference that many people don't understand. This thermostat is unique to the 335 series motors (351C, 351M, 400) and no other motor uses it.

    Even Ford has sold the wrong thermostat over the counter in the 1970s! They actually boxed the wrong thermostat in the box of the right part number. Check out techincal service bulletin number 9, page 11.

    My advice is to use the 333-192 thermostat. The original 351C thermostats were 192 degree thermostats.

    The above info is from George Pence on the Pantera forum and helps to select the correct thermostat. I run the 333-192. The reason for the 192 degree is the 335 series tends to collect condensation under the intake at 180 degrees and running around 192 clears that issue up.

    Hope this helps clear things up, it helped me out as I had the hat style small opening in before and it made a big difference in cooling stability in any situation when I switched to the 333-192 on my Cleveland.
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