400 needs a t-stat

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Jul 23, 2011 | 04:55 PM

F-250 WARHORSE

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Cargo Master

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From: starship enterprise

400 needs a t-stat

I found previously on here that motocraft made a 160 t-stat for a 400 in the right t-stat now I can't find it. Is this right and if so does anyone have the part #. I have a napa in there now and it heats real fast to HOT then cools fast then its fine for a while. Wanted to try a motocraft and see if there is any improvement. Thanks.

Jul 23, 2011 | 04:58 PM

fmc400

MSEE

Joined: Apr 2004

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From: Austin, TX

I realize that this is not the answer to your question, but 160 is way too cool for these engines. They are designed to operate in the 190-195 range. If your engine is overheating, then something is wrong. A lower t-stat is simply a band-aid that may or may not hide the symptoms, but definitely won't solve the problem.

Jul 23, 2011 | 05:01 PM

ford390gashog

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From: Brentwood,CA

I agree you need a 195 in there!!! I also think the t stat you got from NAPA is bad!! Do you Have any other parts stores near you???? There is a better brand and style of T stat to try let me know what stores are around you.

Jul 23, 2011 | 05:03 PM

bamaf150

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From: Mississippi

The 35 year old factory temp guage on my 360 was showing it running to the hot side of the guage and getting there quickly as well. I put a set of mechanical guages in and she gets to 195 deg and no hotter, dont put too much faith in the old guages.

Jul 23, 2011 | 05:08 PM

ford390gashog

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From: Brentwood,CA

Okay the T stat is made by Mr gasket (well not really but that is the package its in) it can be found in the "performance" section at your local shucks/oreily/autozone parts store.This is a balanced failed safe unit! Being balanced with 2 openings in it provides better flow and prevents hot spots in the engine while maintaining true constant temp. This is the same design as used in diesel engines for those reasons. Looks like this Amazon.com: Mr. Gasket 4365 High Performance Thermostat: Automotive make sure to grab a 195 or a 180 if you really want to! That part number from amazon is the same at the local parts store.

Jul 24, 2011 | 05:30 PM

F-250 WARHORSE

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Cargo Master

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From: starship enterprise

I appreciate the help. If a 195 is correct, then I have other problems. The guage hits the top of the "M" in normal and stays there now, no more "Hunting" (I might Have had some air or something) with the 180. its been 100 deg here and running AC and idling, driving, and so on does fine, but when I park its hard to start and then vapor locks. I have to pour cool water on the fuel line or fill float bowl with gas to re-start and keep it running, I wrapped some insulation on the fuel line and this seemed to help, but If I run 195 t-stat, the problem might arise again. This is my reason for a 160-180, and also, what is the prob. with napa t-stats? I would like to know for future reference.

Jul 27, 2011 | 12:17 AM

tbear853

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From: The Shenandoah Valley

You need a Robert Shaw #333-180 or #333-195 Thermostat.

If you get a T-stat just by size, it'll not properly block off the cast in block bypass as it opens, hot water will be drawn back into water pump and recycled and get hotter without going through the radiator.

The Mr Gasket 4365 is NOT the correct T-stat for a 351M / 400 ... or 351C engine.

A drawing of what you need is below to illustrate .... note bottom hat. Without that hat which sets below the "pill", the motor will slowly and surely ''HEAT!" It's purpose is to increasingly restrict flow through the bypass passage way as the T-stat opens when hot coolant hits that pill.

It's the Robert Shaw FlowKooler #333-180 High Performance Thermostat at Summitt:
FlowKooler 333-180 - FlowKooler Robertshaw Series High Performance Thermostats - Overview - SummitRacing.com

It's what you want, it ain't cheap .... but it'll last "years and years" and your motor will love you for it.