oil pressure??
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Freshman User
Joined: Oct 2009
Posts: 41
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oil pressure??
I heard that the 351 motors have problems with oil pressure, is this true?this 78 f-150 with a351m was given to me seem low on oil pressure.when you first start it up,its got 50pounds of pressure,warmed up and at idle,its 0.and i just put in a new mechanial oil gage.so can anyone got the run down on this,
Posting Guru
Joined: Feb 2007
Posts: 1,735
Likes: 2
From: Wingo, Ky
That engine would probably still run fine for years but to fix the problem you need to put in some new main bearings might as well replace the rod bearings to. A high volume oil pump may help some.
Elder User
Joined: Jul 2003
Posts: 668
Likes: 2
Seems I have minimal luck with this sugestion by itself. For me, the Cam bearings always seem to affect oil presure the most on engines I've had. I hope his luck is better than mine.
Zombie Survivalist
Joined: Feb 2009
Posts: 14,809
Likes: 3
From: Rock Springs, WY, USA
The 351C, 351M and 400 are all based on the same design, of the 351C. im not so sure if it is an issue the M and 400 inherited from the C, but they do have oiling issues, and especially to the rear main. for normal use, your M would probably last the life of the truck. once you get more intense with your use, i.e. continuous high rpms, lots of lugging, ect, then you become more concerned with it. there is a way, im not sure of the particulars of it, to run an oil line directly to the back of the motor to oil the rear main, among some other tidbits that will resolve the pressure issues. ask the guys in 335 series engine section of the forum.
Laughing Gas
Joined: Apr 2001
Posts: 868
Likes: 3
From: New Glasgow, Nova Scotia
Yes they have oil pressure issues sooner than most engines and as said a new set of mains and rods will do wonders. If yours is a 4X4 then this is quite simple as you can do it all without lifting the engine, in a 2WD the short way is to lift the engine out completely. I did this to the first 79 I had, 351M and no oil pressure when warm, rolled in a new set of mains and rods and drove the truck for 4 more years with no issues. I have a 78 4X4 I did this to last month and now the oil pressure is great and it olny took about 2 hours start to finish. Good luck
Junior User
Joined: Sep 2009
Posts: 83
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From: Florida, Formaly OHIO
when you do the swap you can also add a oil line that goes from the oil galley beside the fuel pump to the one behind the intake this will help oil flow to the rear bearings of the block which is the weak point of these motors
Posting Guru
Joined: Feb 2007
Posts: 1,735
Likes: 2
From: Wingo, Ky
I think there is a write up of that floating around somewhere with pictures. I need to do that to the 400 in my 79 Bronco, Im pretty hard on her sometimes.
