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Old Jul 11, 2025 | 11:17 AM
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400 oil problems

Any idea for me to look into? I have a 400 in my pick up and I have oil spraying out of the exhaust. I have another thread on here thinking about swapping it out to a 460 that I have in my shed, but if it is simple enough to fix this and swap some parts on to get a little more oomph I might go that route.

Thanks!
 
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Old Jul 11, 2025 | 12:24 PM
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If you have oil in the exhaust I'm thinking your valve guides and seals are the primary culprit. That's the easiest way for oil to get into the combustion chamber and exhaust runners.

If they're worn that bad I'm thinking a total rebuild is in order since the cylinders are likely worn and will need to be bored as well.

You would need to do some additional diagnostics and likely just tear the engine down for inspection to really see what you have to work with.

If you already have a donor 460, accessory brackets, motor mounts, oil pan that'll fit your truck, flywheel or flexplate depending on transmission, headers or manifolds that will work with your truck, dropping in the 460 would be fairly straightforward.

If you don't have all the things necessary to make it work, make sure you consider the cost of acquiring those items when comparing prices to a full rebuild of your 400. The 460 also weighs almost 200# more which is another consideration.
 
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Old Jul 11, 2025 | 12:25 PM
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Also, are you sure it's oil and not just dirty condensation in the exhaust from the truck sitting or raw fuel and you're running really rich?
 
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Old Jul 11, 2025 | 12:26 PM
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The only thing I have is the 460 itself. I don't have any of the accessories at all...
 
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Old Jul 11, 2025 | 02:10 PM
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What kind of shape is your motor in otherwise?
 
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Old Jul 11, 2025 | 02:15 PM
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Originally Posted by mterickson
Also, are you sure it's oil and not just dirty condensation in the exhaust from the truck sitting or raw fuel and you're running really rich?
Yes I am sure, I have to fill up the oil every 4-500 miles usually add 3-4 quarts...

Originally Posted by beartracks
What kind of shape is your motor in otherwise?
seems to be in pretty good shape sounds good, starts right up idles smooth...
 
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Old Jul 11, 2025 | 03:01 PM
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Originally Posted by osris
Yes I am sure, I have to fill up the oil every 4-500 miles usually add 3-4 quarts...



seems to be in pretty good shape sounds good, starts right up idles smooth...
Is a lot of oil.
 
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Old Jul 13, 2025 | 07:26 AM
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A good valve job
And
Have bronze valve guides installed and machine them for the valve stem seals that have the spring that holds them down in place on the new bronze guide
That has been the fix for Cleveland head oil consumption for years and years
Expensive, but worth it
 
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Old Jul 13, 2025 | 12:35 PM
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Pull the valve covers and check the oil drain back holes at each end of the head for blockage, it’s likely some pieces of the old rubber umbrella seals have broken off and plugged or restricted the oil drains
This will cause oil flooding in the heads allowing oil the leak past the valve guides and be blown unburned out the exhaust
 
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Old Jul 13, 2025 | 03:05 PM
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Also check the PCV system.
 
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