Please Help Me Find My Oil Drain!

Ryan Hardy · May 28, 2015

...not the one on the pan. Here is my info:

1991 5.0 LX AOD
SUPPOSEDLY rebuilt to 306
SUPPOSED E303 cam (sounds stock to me)
BBK CAI
75mm MAF (cal'ed to stock injectors)
65mm throttle body
TFS Street Burner intake (why?)
Stock heads
Stock headers
2.5" o/r X-pipe
Flowmaster 2 chambers, dumps

Here is my symptoms:

I do drive it a lot, but I'm going through 2 qts every 2 weeks. No leaks, it is getting burned. Not through the valve guides (no smoke on cold starts). I don't drop the hammer often, but when I do, I leave a faint blue cloud behind me. People have said they could smell oil. When I exit a freeway after cruising at 2500-3000 RPMs (4.10 gears), I can smell oil for a mile. So one would think rings, or shoddy machining (if it really was rebuilt), right?

So I did a compression check. They all looked good. I did a leak down test. Results were better than most new engines. The rings appear to be making good seals.

I shotgunned the PCV, no help. How can oil be getting burned, if it's not the valve guides, nor the rings, nor the PCV?

Any ideas? I'm really stumped. Thanks in advance!

Ryan

2000xp8 · May 28, 2015

Put an autometer mechanical oil pressure gauge in. While it may not directly tell you what is wrong, you will know if your engine is near the end or not. If that is out of budget, get a cheap gauge at the autoparts store and take the sender off and screw it on there, then let the car run for a while.
2 quarts that quickly will probably result in a number under 10psi.

When the engine is good, at idle fully heated up you should be 15psi and up.

It's probably your bearings.

Ryan Hardy · May 28, 2015

Well, that sucks. Thanks for the tip though. I will check the pressure, I have some USGs lying around. I'm sure I have one with the required range.

FWIW, the stock oil pressure "gauge" reads on the low side, and down to about a quarter of the range at a stop light. I know the stock pointer doesn't mean much though.

2000xp8 · May 28, 2015

Oil burning on one of these engines is rarely anything but the rings or bearings.
Everyone talks about the guides but I never actually seen someone come up with that as the cause.

Doesn't exactly sound like the most thought out setup.
So it wouldn't surprise me if it either wasn't rebuilt or done poorly.
An e cam would likely float valves on stock heads at higher rpms.
Never heard of the street burner intake until now.

Start shopping junkyards for explorer gt40p 5.0's.
So at least if it turns out to be catastrophic you will know what your options are.

rbohm · May 28, 2015

2000xp8 said:
Oil burning on one of these engines is rarely anything but the rings or bearings.
Everyone talks about the guides but I never actually seen someone come up with that as the cause.

Doesn't exactly sound like the most thought out setup.
So it wouldn't surprise me if it either wasn't rebuilt or done poorly.
An e cam would likely float valves on stock heads at higher rpms.
Never heard of the street burner intake until now.

Start shopping junkyards for explorer gt40p 5.0's.
So at least if it turns out to be catastrophic you will know what your options are.

not the valve guides per say, but the valve guide seals. when they leak, especially on the intake side, oil can be pulled into the combustion chamber and burned.

Ryan Hardy · May 28, 2015

Lol, I have my option already: '96 351W shortblock. Eventually it will be a 408, but right now I'm pondering the cost of saving my 5.0 vs buying h/c/i and the swap items for the 351. Add the other things like rockers, valve covers, etc and I just don't know right now.

Maybe the best thing would be to just drill out the head bolts to fit the 351, use the stock rockers and pushrods, the cam in my Fox now(whatever it is), then all I need are the supporting swap parts. Far from ideal, but it would get me going with a better, more reliable engine...

Opinions?

rbohm · May 28, 2015

find a set of aftermarket heads at the swap meet for your 351, and use the 302 parts you can for now.

2000xp8 · May 28, 2015

rbohm said:
not the valve guides per say, but the valve guide seals. when they leak, especially on the intake side, oil can be pulled into the combustion chamber and burned.

That is what I meant.
Just not some thing you hear of, especially with stock e7 heads.

If you aren't ready to go all in on the 351, take the ecam (if that is what it is), put it in an explorer engine, change the valve springs, add gt40p headers and go.
Not very expensive, probably make more power than a 351 with e7 heads.

I'm of the belief if u are going to goto a 351, you build something quality and powerful. Just throwing it in there would be more trouble than it is worth.

7991LXnSHO · May 28, 2015

Oil leaking from bearings has ZERO path to the outside or combustion chambers to burn the oil. It can just splash around and get the inside of the block and pan oily. Testing the pressure will give a general guide to engine health.

Low oil pressure does not cause oil loss, UNLESS there is another concurrent problem from bad seals, gaskets, rings (especially the oil ring) or guides.

A budget rebuilder knurled the valve guides to fit the valves in a rebuilder E7 motor I put into first Stang. (Marshall, I think.) It smoked every time you let up (high vac) and when parked on a slope.

Smoking when you get on it sounds like rings. I can not see it passing compression and leak down tests, especially if you squirted oil in and around the bore for a second reading.

Ryan Hardy · May 28, 2015

7991LXnSHO said:
I can not see it passing compression and leak down tests, especially if you squirted oil in and around the bore for a second reading.

That's why I'm so puzzled...

2000xp8 · May 29, 2015

SHO has a good point.

What I should have said originally before scaring you, was check your intake gaskets. I've seen guys with brand new engines botch the lower intake gasket and cause a loss of oil. If it shifted or is the wrong gasket that could cause a problem.
That would be a best case scenario.
Did you check the plugs to see what they look like?

Ryan Hardy · May 29, 2015

Thank you. I wouldn't have thought of that. I will try to check everything mentioned this weekend.

I changed the plugs earlier this year, they were a little wet, but not fouled. Even so, I know they should be dry. I'm thinking I should do the pressure tests again too.

Please Help Me Find My Oil Drain!

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