94' 351W - How long will it last?
 

My trusty old F150 (4x4 SC 351W Auto 3.55) is getting ready to hit 200K miles and I've never touched it except for tune ups and oil changes. It's down of power from when it was new but still running strong and does not burn any oil (does leak a little though). The truck has not been modified and I've not towed anything over about 2K lbs in years.

What do you think the upper end of miles I might get out of her? What's the weak link with these engines that forces a rebuild?

No weak link that I'm aware of. There is a user on here with over 500k on his 351, so anything is possible. There is a lot of luck involved with how long a motor lasts. If you get 200k out of one, I'd say that's about average.

Lots of short trips will typically cut an engine's lifespan.

Keep up on the maintenence and you could see thousands upon thousands more miles. Where is your oil leak? Might be an easy fix.

I do a lot of short trips too as well as highway use on weekends. It's my only vehicle and has been since I got her in 96. I'm pretty anal about maintenance and have never missed an oil change interval by more than a few hundred miles. I've mostly used Mobil 1 with a high quality filter too so that cannot hurt.

The oil leak looks like it could leaking around the oil pan gasket seal, possibly the rear main seal. Hard to tell for sure but the top 1/2 of the engine is clean and oil free. When I change the oil I can always see engine oil on the trans bell housing and the outside of the oil pan is oil covered. It's not that bad so i've just let her mark her her spot on the driveway and not worry about it. One of these days though I should take care of it as it will only get worse. Is there a common oil leak area that I should look at to narrow down the problem?

500K out of this engine :-headbang Oo. That's how I'd feel about that!

My truck is leaking at the rear main seal. I also had a leak at the dip stick tube. You might want to check that as well.

u may want to check the timing chain.
unless 5.8's use gears for timeing

most 302 timeing chains only last 100k to 150k but the 351 is a stronger motor

My truck is heavily rusted from sitting, and the dipstick tube was pretty much gone when I got it. Just replaced it yesterday and there are no more leaks from the tube, however mine continues to leak at the rear seal area like yours. I saw on the web Bar's Leak stop. I am not a big fan of leak stop stuff, but that is an option for you. Dropping the pan, pump etc and/or pulling the trany is a big job. Let me know what comes of it?

My 351 bit the dust with the odometer reading 52k. I have to assume that it was 152k because the age of the truck and the fact that the interior is in great shape. My truck was worked by the previous owner, so it may have shortened the life of it some. The failure on my engine was low oil pressure. I'd invest in an aftermarket gauge so you could have warning before it drops too low. You could repair cheaper parts instead of a complete rebuild if you catch low oil pressure early.

Oreilly auto parts was kind enough to give me a remanufactured engine in exchange for $1100. I hope to only get 100k out of this one since I only use my truck for hauling lots of weight, but at 4k miles a year, that's fine with me.

Mine has 312,000 and still runs great so they will last the timing chain on the 351's are double roller chain and they are much stronger than earlier models

My 302 has 275k miles on it and still runs great. The 4R70W transmission is original also.

You oil leak could be from a hole in the pan like mine is. One day I will have to address it correctly but for now it is the occasional sanding and JB Weld. That and watch the oil level.

Sorry about your loss. My truck was abused also, my oil was sludged up and it took 3 cleanings to get some of the junk out. My pump screen was clogged...

My 95 300 has 204k on it and it runs great. I plan to put another 100k on it. My Dads 83 302 AOD went 220k with its original power train still in good condition. I did have to change out the valve cover gaskets and front timing cover seal at about 140k. The truck had oil changed @ 4k and the tranny oil changed annually. The coolant, PS fluid, and rear axle oil were changed every two years. I even flushed the brake system at 100k. Other than some electronic ignition issues the truck was very reliable. The reason I have a Ford truck today is because of that truck. Frame
rust was the reason I had to get rid of that truck and I needed a van at the time.
Personal record was a 305 chevy that hit 250k and was still going when I lost track.

BTW my son used to work for a transmission parts company and many of the Aerostars and Astros had well over 300k. The sales area covered most of southern NE and the trucks were very abused. Oil was changed once a month.

YMMV
rikrd

My 94 351 had 420k+ kilometers when I damaged the bottom end pushing her too hard up a mountain pass. Thats 250k+ in miles. My trucks history is mostly unknown but had sat for a couple of years before I got my hands on it.