chronic oiling problems with 351 M?
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Senior User
Joined: Nov 2003
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From: London, Ontario
chronic oiling problems with 351 M?
Hi,
Currently I am looking at a 1980 F-150 that has a 351 M in it. I havent looked, heard or seen this truck, it is only on the net. The owner says that the engine has poor oil pressure and doesnt give a reason why. He is asking $1200 in Canadian funds for it and it only has 160 000km (100000 miles) on it. I know that possible causes for the low oil pressure could be old, worn bearings (whether he kept lugging the engine, that burns out bearings quick), a failing oil pump or a bad sending unit. But my main question is are these engines known for poor oil pressure or bad sending units?
Currently I am looking at a 1980 F-150 that has a 351 M in it. I havent looked, heard or seen this truck, it is only on the net. The owner says that the engine has poor oil pressure and doesnt give a reason why. He is asking $1200 in Canadian funds for it and it only has 160 000km (100000 miles) on it. I know that possible causes for the low oil pressure could be old, worn bearings (whether he kept lugging the engine, that burns out bearings quick), a failing oil pump or a bad sending unit. But my main question is are these engines known for poor oil pressure or bad sending units?
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Any old Ford is known for low oil pressure, I've rebuilt 302's with only 50,000 miles on them, the bearing were down to the copper, and no oil pressure. My old truck had a 360 FE that had like 5 pounds of oil pressure cold, and zero hot.
My guess is stock Ford bearings were too soft.
My guess is stock Ford bearings were too soft.
Posting Legend
Joined: Sep 2001
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Bearings are of the same construction in a Ford as in a GM it just depends slightly on the manufacturer, but they are all very very very close. Engine bearing materials are fairly "old" technology. There are some new materials being used tho for special applications.
Bearing wear like you describe is usually caused by dirty oil and/or cheap filters. The particulates will erode the bearings like sand erodes rocks in a sandstorm. Unfortunately particulates multiply in an engine because each particle knocks a few more out of every surface it contacts quickly overloading the filter. Check with the Oil and Lube forum for info on filters and oil.
Scroob is correct tho about the 351M and 400 motors. They seem to have oil pressure problems with higher mileage. Of course a Cheby engine with that many miles would be on the second rebuild...
Bearing wear like you describe is usually caused by dirty oil and/or cheap filters. The particulates will erode the bearings like sand erodes rocks in a sandstorm. Unfortunately particulates multiply in an engine because each particle knocks a few more out of every surface it contacts quickly overloading the filter. Check with the Oil and Lube forum for info on filters and oil.
Scroob is correct tho about the 351M and 400 motors. They seem to have oil pressure problems with higher mileage. Of course a Cheby engine with that many miles would be on the second rebuild...
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GM had a standard wear bearing, and a harder "Delco Moraine" bearing, those lasted a very long time, my brother has a GTO ' 68 with original bottom end, never opened up, the heads were never pulled. The engine has 60 pounds of oil pressure cold, 40 pound hot, and it has nearly 120,000 miles on it. You will never see that with any Ford, most Fords have little or no oil pressure by that time.
There are different hardnesses of bearing materials. A racing bearing is typically harder than a stock rebuild bearing- and can take more pounding without beginning to smear or wear. The sacrifice is, a racing bearing has less "imbeddability", it cannot tolerate dirt as well.
There are different hardnesses of bearing materials. A racing bearing is typically harder than a stock rebuild bearing- and can take more pounding without beginning to smear or wear. The sacrifice is, a racing bearing has less "imbeddability", it cannot tolerate dirt as well.
Posting Legend
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The OEM bearings are all very similar in construction. Yes, there are special application bearings available. Racing engines are not supposed to have as much dirt in them so they can get away with running bearings with less imbedability. Specific examples of good oil pressure can be found in Ford, GM, or Mopar engines.
Posting Guru
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From: Cloud USA
I have 85psi cold and 50 psi hot with 208,000 miles, It all depends how you take care of a motor.
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Post Fiend
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From: Montana Territory
Avoid the M motor if you can, its a piece of junk. If you want the M, there are things you can do to improve pressure and oiling.
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Posting Guru
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From: (near) Denver USA
My mostly stock 351M has had weak hot idle oil pressure for 100K miles now. I romp on it daily, to well over 4K rpm, and it's still going strong (well, as strong as a 351M with a stock cam can) at 185K miles.
Even though I thrash my engine, I keep it well maintained and well tuned.
If you treat an engine like it's junk, it is.
Even though I thrash my engine, I keep it well maintained and well tuned.
If you treat an engine like it's junk, it is.
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From: Elk Lake ON. Canada
How to improve oil pressure
Originally posted by mattsbox99
Avoid the M motor if you can, its a piece of junk. If you want the M, there are things you can do to improve pressure and oiling.
Avoid the M motor if you can, its a piece of junk. If you want the M, there are things you can do to improve pressure and oiling.
cold start it has 50psi once it warms up most of the time it goes right down to 0psi. The dummy gauge is unhooked and I have a real oil pressure gauge. so the # is true.
Can you help?
Steve.
Post Fiend
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From: Montana Territory
I believe the best and easiest fix is installing a Milodon High Volume oil pump, and there is a way to plumb an external line to the back of the motor to improve oiling to the rear mains. That is generally left to people that want to use the motor for racing purposes.
BTW, I take very good care of my motor, it starts up every day, unfortuneatley I have constant problems with it. I don't believe that I should have to change the timing set or the cam or change the internals to get what FoMoCo really wanted out of the motor, they built and tested it before putting it in vehicles, I can't figure out why they still continued to do it even after they knew that there would be no possibility for a racing application.
BTW, I take very good care of my motor, it starts up every day, unfortuneatley I have constant problems with it. I don't believe that I should have to change the timing set or the cam or change the internals to get what FoMoCo really wanted out of the motor, they built and tested it before putting it in vehicles, I can't figure out why they still continued to do it even after they knew that there would be no possibility for a racing application.
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From: Decorah, IA
cantedvalveFord
i can't complain about all fords, sure my 351m had little or no pressure almost all of the time. My 302's have been doing well. My 86 capri has 178000 miles now and it still has excellent pressure, cold or hot. I beat on it a litlle but still change the oil and filter every 3000
i can't complain about all fords, sure my 351m had little or no pressure almost all of the time. My 302's have been doing well. My 86 capri has 178000 miles now and it still has excellent pressure, cold or hot. I beat on it a litlle but still change the oil and filter every 3000
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