How Long a Life?
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Joined: Apr 2007
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How Long a Life?
Alright, I am looking at purchasing a 1978 F150 with a 351M which has approx. 13x,xxx miles (according to the seller). What is the average life expectancy of this type engine? And what can I do to prolong it's useful life? Hoping the owner has cared for it well enough, I know I would.
Hotshot
Joined: Dec 2003
Posts: 18,423
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From: iowa
Welcome to FTE
As to average life, I don't think there is a set answer for that, it all depends on how it was cared for and used or abused. I have seen 351M/400 with well over 200,000 on them still running pretty strong and seen others with less than 75k that needed work.
I would run a compression test, and put a mechanical oil gauge on it and see what the pressures are first off to get an idea of the condition of the engine, also run it with a vac gauge and make sure it's pulling good steady vacuum this will give an indication of condition also.
As to extending it's life, well assuming it's in good condition now, just the basic maintenance, keep the oil changed, change the antifreeze and all other fluids (I do this with any used vehicle I buy) I also run some carb cleaner in the fuel and then change the fuel filter etc.
As to average life, I don't think there is a set answer for that, it all depends on how it was cared for and used or abused. I have seen 351M/400 with well over 200,000 on them still running pretty strong and seen others with less than 75k that needed work.
I would run a compression test, and put a mechanical oil gauge on it and see what the pressures are first off to get an idea of the condition of the engine, also run it with a vac gauge and make sure it's pulling good steady vacuum this will give an indication of condition also.
As to extending it's life, well assuming it's in good condition now, just the basic maintenance, keep the oil changed, change the antifreeze and all other fluids (I do this with any used vehicle I buy) I also run some carb cleaner in the fuel and then change the fuel filter etc.
New User
Joined: Dec 2001
Posts: 12
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From: Osceola USA
The 351m are known for the oil returns getting plugged, I would take the valve covers off, and look at the heads. I have seen many run for 200K plus it just depends on how the engine was taken care of. Check Oil Pressure and Vac. Usually when I get something like that from someone, I will go through, and change timing set, Oil pump, and all fluids.
Laughing Gas
Joined: Dec 2000
Posts: 781
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From: East Texas
As you can see from my sig, the 351M in my 77 made 315,000 miles before rebuild. Oil pressure was plenty low prior to the rebuild, still ran strong though.
Changing the timing set is a good idea if it has not been changed. The factory set consisted of nylon gears which did not lead to a long life. I changed to a double roller set about 30,000 miles prior to rebuild.
Changing the timing set is a good idea if it has not been changed. The factory set consisted of nylon gears which did not lead to a long life. I changed to a double roller set about 30,000 miles prior to rebuild.
Cargo Master
Joined: May 2003
Posts: 2,561
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From: Earth
The 400 in my '79 has right around 190,000 miles on it. I need to get another 2-years (10-15k) out of it before I can afford a rebuild. The valve guides have been going out for the last 50k as it smokes on start up. I'm going to replace the timing chain and water pump this summer. It still runs good, but it is closing in on rebuild time.
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Thanks to all. I figured that if you care for your Ford, it cares for you. The guy also said that he replaced the oil pump. If I decide to purchase, I will definetly check all the suggestions you speak of.
I'll have the Roast Duck
Joined: Jul 2002
Posts: 9,622
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From: Northshore, MN
my experience has been the rear main seal. Maybe it's an "up-north" thing, freeze, thaw, freeze, thaw, etc...
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havi, thanks for the reply. That issue you mention supposedly has be addressed by the current owner and has been replaced. Every little thought and idea helps me.
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