[DeTomaso] Thermostat restrictor plate 351 C

Tue Jun 10 22:05:16 EDT 2014

Third time is a charm?

Hi John,
I've been monitoring the replies all day; didn't get a chance to reply
until I got home.

I think what's missing here is the bigger picture.  "Why are you asking
this question?  What is the problem you are trying to solve?"

Even if you're just after some head knowledge I'm hoping what follows
will be useful.  :)

Most people continue to have a 351C (Cleveland) in their Pantera.  Some
have substituted a 351W (Windsor) while some later Panteras came with
them stock; others have put various other makes and model engines in. 
We'll confine this dissertation to the 351C as it's the most common and
is the reason the whole "restrictor plate" question comes up.

The 351W does not use a restrictor plate, so we'll just take it off the
table completely.

The restrictor plate is actually a bypass "helper."  It's a round piece
of metal with a large hole in the middle.  During warm up of the engine,
some coolant goes through this hole bypassing the radiator and
recirculating immediately to the engine.  This is of course assuming one
has a stock style water pump and -not- one that has the bypass passages
sealed off.

Once the thermostat opens, and you are using the proper thermostat, the
passage becomes very restricted and there is virtually no coolant flow
bypassing the radiator anymore, though a small amount still does.

Here are the photos.
This is a restrictor plate in it's factory original position.  You can
see it's installed in a recess cast into the block deep inside the
thermostat port.  When the thermostat is closed, no coolant goes out the
top of the block but it has to go somewhere or it just boils in place. 
It goes through the small hole in the restrictor plate and into the
water pump:
http://teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=2639

You asked about a photo of the front cover without a water pump
attached.  Let me go one better.  Here is a photo of a long wire-tie
going through the top of the bypass hole and existing the front of the
block at the water pump bypass port:
http://teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=3077

The water pump port it goes into is shown in this next photo.  What you
have to pay close attention to is that the bypass goes -two- ways; one
is toward the heater core, shown by the wire-tie exiting the heater hose
port, the other is behind the wire-tie as you see it and leads directly
to the water pump impeller; you can just see the open hole behind the
wire-tie:
http://teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=3071

The coolant that goes to the heater core also travels back into the
block at the other heater hose port and you can see with this photo how
it ends up just over the top of the restrictor plate:
http://teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=3080

Please note I don't really know which way the coolant is flowing through
the heater core in either position of the thermostat; all I did was
illustrate the path.

Within the water pump, the bypass flows back into the engine through the
larger two ports after passing by the impeller.  I'm sorry I don't have
a photo of that, but found one on the Internet:
http://i.ebayimg.com/00/s/MTA2M1gxNjAw/z/MysAAMXQySpRS8if/$T2eC16N,!yUE9s6NDMc9BRS8ie8NuQ~~60_35.JPG

This is the back side and it mates up to the front of the engine that
looks like this:
http://image.mustangandfords.com/f/58890193+w650+h650+cr1/aluminum-351-cleveland-double-roller-timing-chain-1.jpg

By the way, that's a new ALUMINUM 351C block (by Todd Buttermore)
Anyway, on the left, you see a large square port and above and to the
right you see a round port, just below another round port that is for
the temp sender, right below where the thermostat goes.  The two large
squarish ports are the INLET to the block from the water pump.  The
smaller round hole is the BYPASS OUTLET to the water pump.

Now, if you have a water pump that has no bypass port, like the one
below, then the restrictor plate doesn't matter much because as
illustrated with the wire-tie earlier, there's no place for the coolant
to go:
http://www.supermotors.net/getfile/802687/fullsize/8209impeller.jpg

But let's say you have a standard water pump with bypass.  Alright, so
the thermostat has opened, and if  you have the correct thermostat it
should block the flow of coolant to the bypass port.  Here we see what a
proper 351C thermostat should look like, see the little "hat" on the
bottom?:
http://teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=2645

I've got a screwdriver shoved in there to open it so you can see the
"hat" better.  Next, I ripped that thermostat apart just so I could
create this photo where you can see the "hat" sits in the large hole
restricting the flow through the bypass:
http://teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=2657

So with the bypass essentially closed, now the coolant circulates
through the thermostat, through the radiator, back to the water pump and
back into the engine.  It can also pass through the heater hoses and
heater core as that path through the water pump is -not- blocked; it's
just not passing through the bypass port anymore.

Here is a photo of an IPSCO or Marlin Jack restrictor plate compared to
a stock one:
http://image1.cougparts.com/sc/images/10003234_2.jpg

The recess in the IPSCO model is to accommodate the regular thermostat
opening.  The small hole is helpful for getting air out of the system
and also allows a minuscule amount of coolant through; I would venture
negligible for warm-up purposes.

If you did not have a restrictor plate, then I think you'd be chasing a
constant overheating problem.  Are you?  If not, then I think your
restrictor plate may be in place.  It's easy enough to check, well....
not -that- easy on a Pantera as you have to get in there typically from
the passenger compartment, but two bolts to undo the housing, lift the
thermostat out and there you go, is it there or not.

If on the other hand you see this:
http://www.351c.info/gallery2/v/asajay/351C_Build_2001/stat.jpg.html
That means you have a 400 and NOT a 351C, which is very doubtful.  Note
this photo does not have a recess for the restrictor plate, the
restrictor is actually -cast- into the block.

On another occasion in a different engine, I decided to plug the
restrictor plate hole, you can read about how I did that on the same
Team Pantera Racing web site I linked to most of the other photos. 
There is more there from the TPR division of the Pantera Research
Institute, browse around and if you have any questions, let us know.

Hopefully this has been helpful,
Asa  Jay

-- 
Asa Jay Laughton, MSgt, USAFR, Retired
& Shelley Marie
Spokane, WA
******************************     
http://www.racingagainstautism.com
http://www.teampanteraracing.com
http://facebook.com/racingagainstautism