Normal operating temp for a 78 351M

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Jul 25, 2002 | 02:49 PM

airharley

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From: Escondido, CA

Normal operating temp for a 78 351M

I have a friend who has a 78 F-150 Ranger with the 351M. He is having problems with engine temps. His main concern is how hot does the 351M run when sitting idle, cruising, and towing. He tows a old boat around. I have gone through the whole engine troubleshooting with him but nothing seems to be out of the norm. ie... thermostat, radiator cap, timing, water pump, block fushing, and the whole 9 yards. Any idea what the temps are would be a great help. He says it runs around normal no load 195 degree, then rises when towing which is normal of course. Thanks.

Jul 25, 2002 | 05:30 PM

Franklin2

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From: Virginia

Normal operating temp for a 78 351M

In the worst situations, if it never went above 230, I would say it is normal. Constantly going above 230 would be reason to investigate.

Jul 29, 2002 | 10:42 PM

sixftsix

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Normal operating temp for a 78 351M

One thing I found out ( the Hard way) Make sure you have the correct Thermostat. The M Engine uses an internal coolant bypass, and the Correct Thermostst has a small "collar" around the sensor on the bottom of it that extends and closes the bypass when the thermostst opens. If you are getting strange overheating problems, this is a good place to start looking!

Jul 30, 2002 | 11:04 AM

Pentekno2

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From: KC Metro

Normal operating temp for a 78 351M

the 351m runs from 190 -200 with no engine load doesnt it? My 351m was recently rebuilt and it had a pair of numbered gauages installed, and after it warms up it sits at about 200.

Aug 2, 2002 | 04:47 PM

cigarxtc

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From: North of Tulsa, Oklahoma

Normal operating temp for a 78 351M

My 78 351m runs between 'R' and 'M' of the stock NORMAL gauge settings. I replaced the thermostat with a 180 degree a few months ago and she never gets above the end of 'M', even in stop and go traffic during these hot summer days in Tulsa.

A quick and easy coolant check would be the coolant to water ratio. Most manuals say 50/50 mixes, but I use about 30 coolant and 70 water. Also, spraying the radiator fins out with the garden hose might help alleviate the heat problems.

Aug 11, 2002 | 01:02 AM

F350SuperCab4x4

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From: Phx, AZ

Normal operating temp for a 78 351M

i have a 78 with a 400 (same motor) and it runs about 200-210 and i have the HUGE radiator. i thought that was kinda hot myself. but then again im in Phx, AZ

Aug 21, 2002 | 12:18 AM

PapaBlue

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Normal operating temp for a 78 351M

I have a 78 F-250 with a 351M and Automatic transmission. Over the years I suffered with over heating in stop and go California traffic and when standing at idle during the summer for 20 years.

I recently rebuilt the engine after 200,000 rough miles (highway, back country and daily city) and found the right rear corner of the water jacket (around #4 cylinder) mostly pluged with a solid rusty buildup. After boil-out the block, I chipped out all of the rusty junk before the rebuild. Over the years I have tried every thermostat in the book from 0(none), 160, 180, 195 and 210. I have also tried several coolant percentages with no joy.

As part of my rebuild I installed a 4 row SuperCool radiator in place of the original 3 row. "Sha-zam", problem solved. With a stock 195 degree thermostat in place, the temperature gauge reads 1/3 scale all of the time after warmup. Even on the hottest days (100+ degrees). I no longer suffer from over heating or driveway puddles when I shut it off.

Flush it and give it some surface area and you will enjoy. Don't forget the correct T-stat. The stock temperature range is usually the best performer. Good cooling also keep an automatic transmission happy and lasting longer. A trans-cooler when doing a lot of towing can't do any thing but help.

PaPa Blue