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This doesn't look good!

Big Jim F150

73-79 Ford Trucks Rock
That's strange that you guys have trouble finding thermostats for the M Series engines 351M / 400. Try the local Ford dealer, they could get you one, for last year while my78 F-150 Ranger Lariat was at the Ford Dealer for distributor issues, while it was there I had them put a new thermostat in for me, and they didn't have a problem getting one. So Doug try your local Ford dealer and see if they can get you one, for you have the same engine in your truck, that I have in my truck, the M Series 351M / 400.smilieFordlogo smilieFordlogo smilieFordlogo smilieFordlogo hopefully you find this helpful.
 

fatherdoug

Tonto Papadapolous
That's strange that you guys have trouble finding thermostats for the M Series engines 351M / 400. Try the local Ford dealer, they could get you one, for last year while my78 F-150 Ranger Lariat was at the Ford Dealer for distributor issues, while it was there I had them put a new thermostat in for me, and they didn't have a problem getting one. So Doug try your local Ford dealer and see if they can get you one, for you have the same engine in your truck, that I have in my truck, the M Series 351M / 400.smilieFordlogo smilieFordlogo smilieFordlogo smilieFordlogo hopefully you find this helpful.

They don't have one and can't get one.
 

fatherdoug

Tonto Papadapolous
Whats a good price Doug ?
Just saw this one is a 195*

http://www.ebay.com/itm/271664504517

That one disappeared. Somebody must have bought it. :D Thank you, Mark.


Thank you, Randy. I think some of those will work, but I'm not sure of the quality. The one Motorcraft that is listed is an RT-1139, which is for a Windsor engine. I need an RT-139.
 
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10
FYI...351C and 351M/400 do not use the same thermostat.
351M/400 do not require the "top hat" on the thermostat.


351C block

38998dab865f4a11e2103513fa12053c.jpg



351M/400 block

f48b5f3d7439251e761dbf679f367ef8.jpg
 

fatherdoug

Tonto Papadapolous
Thank you, Tim. Now I'm confused, if I remember right, the thermostat well on my 400 looks like the top picture?
 

DNFXDLI

The Token Canadian
Staff member
FYI...351C and 351M/400 do not use the same thermostat.
351M/400 do not require the "top hat" on the thermostat.


351C block

38998dab865f4a11e2103513fa12053c.jpg



351M/400 block

f48b5f3d7439251e761dbf679f367ef8.jpg

I'm confused as well now....I just went and looked at my block and it is the way the 351C shows :suspicious:
 
43
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See...we are human. I went and looked and found a few other 400 blocks that look like the 351C water outlet.

This thermostat we purchased from a local Carquest. We used it in a 351C engine.
Part #30089, just a few bucks.



1c336ccd95c986414f95bd186b698018.jpg
 

fatherdoug

Tonto Papadapolous
43
10
OK...I have totally screwed up now!!!

The pictures that I have posted about the water outlet, I have them labeled backwards.

The large hole, is the 351C outlet, but without the brass restrictor.
Hence the larger hole.

SO...the 351C (top-hat) style of thermostat should not be needed in the 351M/400 block.

I am very sorry for any confusion I may have caused, when you look at Ford and Cleveland style blocks all day, I can confuse myself.
 

fatherdoug

Tonto Papadapolous
With the amount of work that you have done to remove the 400 from boat-anchor status, you're forgiven. Thank you.
 
43
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Thank you!!

It does make me feel kind of dumb.

But as far as "boat anchors"

I am feeling that with the latest builds, we have a 434 that has now made over 620 HP on the street, if it fits, it can be the better choice.

Now the advantage that the 400 has, is in the last few years of being in a truck, I feel the casting are thicker and stronger.
If a 351C block was making 600 HP on the street, it probably would not last very long before it split the cylinders.
 

fatherdoug

Tonto Papadapolous
Boiled Thermostat for lunch. :D This NAPA 195* thermostat started opening at 185* and was fully open at 195*.

Might try this one until another one arrives.

IMG_003724.JPG
 

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