Hi, Id Like To Thank Everyone For The Help On The Back Gas Tank. Got It Done This Week. Now I Am Having Oil Pressure Trouble. How Many Miles Do You Think A 400 Should Be Able To Get Out Of It? I Have Low Pressure At Idle And At Speeds Over 45. At 45 It Is Preety Good. I Got A New Sending Unit Tonight, But Didnt Get It On Yet. I Have Around 140 Miles On It Now. Also Would You Rebiuld It Or Replace It With A Different Size?

 

I think your gonna open a can worms with that question,so I might as well start.Pull that thing and go with a 429-460 or 302-351.Though I have seen some strong 400's , I've seen alot more problems with them.I guess it depends on what you want and what you want to spend.

 

1st when you use cap's at every word it make's it hard to read what it is you are trying to say.

How hard do you drive it? How often do you change the oil? Do you drive in dusty condition's a lot? It all is relevant to the life of an engine, it all depend's how you care for the motor. I would think a 100,000 is a good number.

140 miles on what?

I would rebuild or do an engine swap as well if that is the question.

I would not follow this opinion tho, I don't know why SRD4X4 would put a 302 in place of a 400? Not that it would fit in there very easily, wrong tranny, motor mount's, exhaust and so on. Stick with the 429 or 460 for a swap.

 

Sorry about the CAPS. didnt see that it was locked down. Just got the truck so I dont know how it was treated, but everything else on the truck was in good shape. It has 140,000 on it. I was just wondering if anyone has found the sending unit to be the reason for pressure to go from good to bad?

 

I think that the 400 has a bad rap. The biggest problem was the factory had them way detuned for emissions reasons. I rebuilt my 400 for a realatively low amount of money and added lots of performance parts, I am very happy with it as far as gas mileage and power. If you have any questions on the parts to use when overhauling one E mail me. As far as the the low oil pressure it is fairly common for the to need rod and main bearings around 100,000 miles.

 

I am with you in that I do not understand why you would have good oil pressure at 45, only to have it drop as you speeded up. All I can think of is that you are opening the bypass on the oil pump and once opened, it sticks.

I like the FE motors, but I did rebuild a 400 once and got good service from it. My guess is that unless you want to build a hot rod it is best to keep what you have - always cheaper and easier to reuse something rather than doing an engine swap.

Since you do not know anything about this engine, there is little differance between rebuilding it or using it as a core for a quality rebuilt 400 - whichever you are comfortable with. Both should give you 100K of good service.

 

If money is an issue,re-build what you have.If not,and you have the time,swap in a 429-460.That's just my opinion,not my recommendation.Don't want to "ruffle any feathers".Hey,as long as it's not chevy orange,it's all good.

 

I was in your position last year at this time. I had just bought a 77 f-150 with a tired 400 in it. I had the same problems with the oil pressure and hoped I could make it last. What I found was the oil drain holes were plugged with sludge causing the low oil pressure at higher speeds. This was an easy fix; I ran a brass brazing rod through the hole to clean them out. This is a common problem on this series of engine. Also common is the low idle oil pressure. This is from the main and rod bearings wearing.

As for how long your motor will last... good question. I chose to rebuild another 400 to drop in because I'm **** like that and didn’t want it not running right. After I pulled the engine, I found the cylinders pretty worn as well as the valve guides and main and rod bearings. I could probably have ran this motor easy for a long time though. It had nearly 150k on it.

On the swap I would go either way. They are both very good engines.

If you want to keep the 400 and need advice visit the 335 series forum. Lots of brain power in there.

 

I see alot of good advice here. I also say 100K Plus. My dad had a 400 that went 300K.

Also, never, ever trust the stock guage. Stick a mechanical guage in there and see what it tells you. The stock guages are nothing more then fancy idiot lights.

 

If you're getting low oil pressure at certain speeds, but not at others...I'd first start with pulling the pan, and replacing the oil pump. Get a new pan gasket while you're at it. Can get a good high volume oil pump for around 40-60 bucks depending on where you buy it. May as well replace the pump drive shaft while you're at it(about 8 bucks, these are Canadian prices, will be less in American money) The second thing I would do is called an oil change tune-up. Buy yourself two oil filters, some cheap oil(less one liter, use 1 liter ATF in it's place) for the first oil change(liter=quart, roughly) Take the truck for a good hard, up to operating temp, run. Come home, change it right away, add a fresh filter, and some good quality oil, and it should stay clean for a while longer, as well as remove the sludge in the engine. It may take more than one change on the cheap oil with the ATF mixed in. The reason I say use 1 liter of ATF, is that it's super high in detergents compared to regular engine oil, but at least it's a lubricant, where that engine flush crap isn't. I also usually leave the drain plug out, and pour about a liter of diesel fuel into the fill hole, and let it run through as well, but prior to installing the cheap oil. This way the remnants of the diesel are gone with the next change as well. I use the 99 cent/liter Canadian Tire oil for this trick, and then switch to a decent brand name afterwards for everyday driving.

 

We have a 75 F-350 with a 460 that has been doing this for years. I have always assumed it was the sending unit because the engine shows no signs of low oil pressure.

 

My 400 has 230,000 miles on it and the new alternator makes more noise than the motor. I would drive it anywhere in the lower 48 this time of year.

 

Thanks guys, i think i will try the atf with the oil and a new sending unit to see if that helps. i think ill try to get thro winter before i rebuild. sounds like the 400 is a good motor to stay with. when it get alittle warmer out ill be back looking for more help on the rebiuld