sibo191

So I'm freshening up my 96 f150 efi 5.0 it ran ok at the time I had it tested (for a second opinion on my gauge.)

All cylinders have a fairly even compression between 140 and 151 psi. I believe stock was somewhere around 180ish?

There was also a little white smoke, either until it warmed up or if it idled too long. Not a ton of smoke but definitely some there.

Are new rings necessary?

There was also a slight tapping probably valves and occasional slow tough vibration.

I'm planning to either replace or rebuild the heads depending on cost. And add some breathing upgrades. And replace the vacuum system as it's all pretty rotten.

Anything else I should look at? I have the engine out but haven't started messing with it yet.

RLXXI

Any compression reading above 100 psi is good. If they are all within that 140-150 range I wouldn't think rings would be an issue. Possible head gasket, worn valve guides for the smoking part, hard to say without putting hands/eyes/tools on. How many miles on the engine. Might just be time to go thru it.
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sibo191

Its definitely time. Sitting just over 400k.

I'll definitely give it a good look over when I have some time. Have to change the oil pan gasket and rear main seal anyway... Why I pulled the engine to begin with.

RLXXI

Damn !!! half a million miles almost and has growing pains. Sounds like you found a solid machine to consider keeping alive.
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Steve83

This caption explains how to do & interpret a compression test:


(phone app link)

Rear main seals don't just fail. If there's an oil leak from that area, it's most-likely from the crankshaft bolts NOT being sealed (with threadlocker) the last time the engine or trans was out.

sibo191

Worth the effort. Just finding the time.

RLXXI

Or some idiot ran the bolts down with an impact instead of torquing them properly creating humps where the seal rides permanently damaging the crank shaft.
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sibo191

Thanks for the link Steve was some useful into in there.

To the best of my knowledge the engine hasn't been removed before. I have work order a on it for the 8 years prior to my owning it and I haven't in the 10 I've had it. So only a few years prior that I doubt it would have been opened up.

Perhaps just the oil pan leakinging in that area too... I'll know more .When I clean it up and get a better look around.

Steve83

That's me, and I've never had a rear main leak. I've certainly never seen a crankshaft hub deform from its own bolts. Land Rover, BMW, Mitsubishi, Saab, VW, Ford, Honda, Nissan...
All leaks run down & back to that area, so I doubt there's anything wrong with the RMS. Always follow leak trails forward & up to their sources - most likely the valve cover gaskets &/or timing cover gasket.


(phone app link)

The best VCGs for these V8s are original Mahle rubber-lined steel. I bought new ones for that engine, but decided to clean & reuse the originals:


(phone app link)

If yours already has them, then I doubt they're leaking.

RLXXI

Go buy a lottery ticket.
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