# Ford 300 six low oil pressure



## PhilJohnson (Dec 24, 2006)

I have a 300 six in my 77 Ford F-100. It seems to have real low oil pressure at idle. It doesn't knock or tick, but according to the factory gauge it drops down to next to nothing. When I first start it up the oil pressure is pretty good. But after running it for a while especially on the interstate it gets real low. It has about 260,000 miles on it, I don't think it has ever been overhauled. Could this be a case of too much sludge or a worn oil pump, or am I out of luck here?


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## Beeman (Dec 29, 2002)

First thing to do is hook a mechanical gauge to it and get an accurate reading. Ford 300 6 cylinders are tough engines but do wear main and cam bearings causing low oil pressure. A clogged oil screen would cause oil pressure to drop at highway speed or when revving engine. Don't panic, my 300 knocked for thye first 8 years or so when i bought it. I didn't change the oil for that time until I changed the motor. It was running fine when I pulled it to replace it knock and all.


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## Old Vet (Oct 15, 2006)

What you are describing is worn main bearings. To test this put a higher weight of oil in it and see if the oil pressure is better. If you use 30W10 oil use 40W15 or straight 40 weight. IF this cures your problem You have two choices us the higher weight oil or repair it.


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## agmantoo (May 23, 2003)

Just a straight 30 wt. and a new motorcraft filter could make a big change. Multi viscosity oil and high mileage do not necessarily go together IMO. Tired iron has different needs.


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## PhilJohnson (Dec 24, 2006)

I am going to pull the engine this weekend. The oil pump is getting replaced with a high volume type. I also am changing out the blown up trans too. Would it be a good idea to change out the cam and main bearings while the motor is out? Or should I just see if there is a bunch of play in the crank and cam?


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## Rocky Fields (Jan 24, 2007)

Hey.

260K, the engine is on it's last leg. I'm surprised timing chain hasn't jumped by now.

If you use a high volume pump, you need a higher capacity oilpan. You want a high pressure oilpump with the stock pan.

You need to replace rod and main bearings for quickie fix. Leave cam bearings alone.

RF


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## FL.Boy (Dec 17, 2007)

At idle you can have 7 psi and be fine for ever 1,000 rpm you only need 7 psi.


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## Rocky Fields (Jan 24, 2007)

PS: You want racing/wider clearances on the bearings with high pressure pump. Stock pump is used with stock clearances on bearings. Normal procedure is to inspect and mike crank journals to see if oversize bearings/crank cutting/polishing are required. You could use plastigage for clearances. Crank may be scored and will damage new bearings. Maybe new stock bearings if crank is good with new stock oilpump would be better. You won't know for sure until you see the crank condition and measure...also, mailorder auto places sell crank kits or maybe order one locally if required.

Personally, I'd get a good engine from another vehicle(clunker)that I inspected and heard run first.


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## PhilJohnson (Dec 24, 2006)

Rocky Fields said:


> PS: You want racing/wider clearances on the bearings with high pressure pump. Stock pump is used with stock clearances on bearings. Normal procedure is to inspect and mike crank journals to see if oversize bearings/crank cutting/polishing are required. You could use plastigage for clearances. Crank may be scored and will damage new bearings. Maybe new stock bearings if crank is good with new stock oilpump would be better. You won't know for sure until you see the crank condition and measure...also, mailorder auto places sell crank kits or maybe order one locally if required.
> 
> Personally, I'd get a good engine from another vehicle(clunker)that I inspected and heard run first.


Since the engine is probably a little worn I figured the clearances aren't real tight so a higher volume oil pump may work a little better than a stock volume one. I am crossing my fingers that cleaning out the 31 year's worth of sludge and a new pump will give me another 30,000 miles. Truck doesn't get driven much. I have put 20,000 miles on it in 5 years. It doesn't have any blow by or smoke at all. Although I got a feeling the compression is a little low, compression usually isn't enough to keep the truck from rolling even on a relatively mild hill. The big concern is on a long interstate trip at high speeds (70 mph +). I take it down to Milwaukee a couple times a year which is a 480 mile round trip.


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## HermitJohn (May 10, 2002)

Rocky Fields said:


> Hey.
> 
> 260K, the engine is on it's last leg. I'm surprised timing chain hasn't jumped by now.
> 
> ...


First 300s dont have a timing chain, they use gears.

If the crank and cam journals are smooth and dont have grooves you can replace bearings. This is unlikely at this point.

But just swapping bearings and playing games with oil pumps and heavy oil are short term fixes. Even as is it will last some time, its a very tough engine, you just wont know when it will go, so if you just use it once in a while to get feed or go to dump, not going to matter. However if you depend on it as a daily driver, find some retired guy with backyard machine shop that rebuilds engines and probably cost around $800 to rebuild engine properly and get another 300k miles with few worries if you take care of it. That way you remove and replace engine once and dont have to constantly worry and fiddle with it. 

Good used engine for under $400. Though last of these engines made in like '95 so even best of these used most likely will have well over 100k and you get to guess how much they have been abused. Worth extra if you can buy a running version that you can test oil pressure and compression as is true on any engine though oddly few people bother doing this when buying a used car.


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## Beeman (Dec 29, 2002)

I'm guessing you didn't check the oil pressure with a mechanical gauge. You're trusting a 30 yo factory gauge which is just as worn as the motor. If you just want to take a chance put in a new pump and a set of rod and main bearings. I wouldn't play with oversize, just go with what the old ones are which should be stamped on the back of them. Be sure to check what the old ones are as they might be for an undersize crank already. Replacing cam bearings requires cam removal and a special tool to remove and install them. I guess a high volume pump might be OK to compensate for all of the leakage at the bearing clearances but I would just go with standard volume. 
Personally I wouldn't do any of this especially if the engine showed acceptable oil pressure and didn't knock. Change oil, use a Motorcraft filter, add Lucas oil treatment and lead a good life.


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## clovis (May 13, 2002)

Beeman said:


> Change oil, use a Motorcraft filter, add Lucas oil treatment and lead a good life.


I second the Motorcraft filter. You should be able to pick one up at other places than the Ford dealer.

I almost posted the suggestion about Lucas oil treatment. I am hearing good mechanics swear by that stuff.

Clove


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## haypoint (Oct 4, 2006)

After 260,000 miles, most engines are worn out. There are no quick fixes for worn out. It is likely that the oil pump is badly worn. It is also likely that the bearings are worn. Both will cause oil pressure to be low.
You can do a bottom half repair, new oil pump and new rod and main bearings. You won't get another 260,000 miles out of it because you won't have a crankshaft bearing surface at the correct diameter and smoothness as a new or turned crank will have. With that done, you'll see an increase in oil pressure, unless the cam bearings are also worn. Quite possable. After 260,000 miles, the rings are generally worn, the cylinders worn and the sides of the pistons worn. Even with hard valve seats, 260,000 miles they are going to need some attention. Where to start and where to stop.
The 300 Ford is among the greatest engines Ford ever built. But your's has been drawing social security for awhile.


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## PhilJohnson (Dec 24, 2006)

Haypoint, point taken. But even if it only last another 30,000 I'll be happy. Right now I don't have the time or a decent garage to rebuild the motor, and it is hard getting motivated to do any thing when it is 10 below outside  I guess I'll take my chances getting rid of sludge and putting in a new oil pump.


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