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Porous block

R

RD400HP

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Location
Fowler, Ohio
I'm going to go look at a 6.5 short block that's on Craigslist. The seller claim's that it was replaced under warranty at 30K miles because the block leaked oil. Dealership claimed the block was porous and that was why oil seeped through the block. Anyone ever hear of this?

Mark
 
If it really is porous I'd be leary of how strong the block will be. If it was an engine that didn't have a bad rep for cracks and such I would consider sealing it.
 
Porosity in a casting is not uncommon but one that will cause an oil leak is usually caught in quality control I would think. You hear about more air leaks/coolant leaks in the head than oil leaks.

I remember in manufacturing class they discussed porosity in a castings. If the molten metal is not quite hot enough and poured too fast it can traps some air in the mix it will leave void air pockets. The metal is "steaming" hot so it will gas out some too not just trap air in the mold.

Then too metal like most things shrinks as it cools so the smallest of voids get bigger as the metal around them shrinks away. Its fairly a bit like a black art to get a casting just perfect. Thicker sections cool slower than thinner sections so you get a residual stress build up from different shrinkage rates and voids can form from just the difference in cooling rates if severe.

It just depends on where the void and porosity is as to the severity of quality concern. It could be fine but some porosity near an oil gallery and the block fine. Or it could have other problems. Only way to tell for sure would be expensive X-rays. They usually air/coolant pressure test the heads I have never heard of this type testing for the oil circuit (I guess an oil leak would tend to leak internally and drain back to pan and be ok if oil pressure was ok).

How are you going to seal the oil leak or live with it????
 
racers use glyptal sp? to seal the lower end and make the oil run back to the pan faster. Obviously if it was a leak in the pressure side it wouldn't be sealable. I was assuming the block was sweating.
 
Yeah, porosity could have different meaning. I think mostly its small holes or cavities randomly spaced and sometimes they touch and can have a path that doesn't seal a pressurized area. Most holes don't have to be round and are more a function of the "out gassing" and thicker areas molten metal cooling and shrinking away. Usually thin areas near to thicker areas are more problematic for this like in the heads. I think the block is thick enough that it is more rare for a problem to occur.

It would be really bad if it was like an open cell foam that seeped out oil. Cast iron is "grainy/sandy" but should be alloyed and the material thick enough to make it is solid "closed cell form".

Now the texture of cast will have a lot of surface area if you looked at the surface metrology its bumpy grainy rough and why it will look oily and hard to clean from the tiniest of oil contamination. You can't really polish it or get it to a nice smooth shiny surface of like a tool steel or something alloyed with chromium sp?. But again its still closed cell crystalline structured just not like more alloyed steel that has a much finer crystalline grain structure. I can't remember specifics maybe the "oxygen wash" or what ever it is that turns iron to steel by stripping the excess carbon frees up the crystalline structure so it more uniformly forms ????
 
Thanks for the input guy's. I called the seller to get a little more info on it but no answer. He wants $100 for it ,I thought for that price and 30K miles on the rotating assembly that it would be worth that.

Mark
 
They fix porosity on LS2 V8 engines with RTV or epoxy depending on where the aluminum block is leaking. Some are prone to this in specific areas esp near rear mains.

There are ways to fix it. I would suspect a crack, but, check it out and confirm the source of the leak.
 
I talked to the seller today he said it leaks oil through the block nothing to do with oil pressure. The only numbers he could find on the back of the block is 10237141. Does anyone know what year this block is from these numbers? Thanks.

Mark
 
Mark I saw that one also... Thought about it.. Na. Not because of the oil leak... But because I have a garage full of keeerap already. It's getting hard to walk through.

Best of luck. I'd be interested in seeing this one.
 
schiker said:
Yeah, porosity could have different meaning. I think mostly its small holes or cavities randomly spaced and sometimes they touch and can have a path that doesn't seal a pressurized area. Most holes don't have to be round and are more a function of the "out gassing" and thicker areas molten metal cooling and shrinking away. Usually thin areas near to thicker areas are more problematic for this like in the heads. I think the block is thick enough that it is more rare for a problem to occur.

It would be really bad if it was like an open cell foam that seeped out oil. Cast iron is "grainy/sandy" but should be alloyed and the material thick enough to make it is solid "closed cell form".

Now the texture of cast will have a lot of surface area if you looked at the surface metrology its bumpy grainy rough and why it will look oily and hard to clean from the tiniest of oil contamination. You can't really polish it or get it to a nice smooth shiny surface of like a tool steel or something alloyed with chromium sp?. But again its still closed cell crystalline structured just not like more alloyed steel that has a much finer crystalline grain structure. I can't remember specifics maybe the "oxygen wash" or what ever it is that turns iron to steel by stripping the excess carbon frees up the crystalline structure so it more uniformly forms ????
Click to expand...
In bygone days the raw castings where left to "cure" for a year before machining,not so today
 
RD400HP said:
I talked to the seller today he said it leaks oil through the block nothing to do with oil pressure. The only numbers he could find on the back of the block is 10237141. Does anyone know what year this block is from these numbers? Thanks.

Mark
Click to expand...

141 was pre 506,s 96 or so.
 
For $100 bucks, I would grab it and tear it all apart and hot tank the beotch.

You should be able to figure out wassup with the leak.

IMHO, far too many stealers dont have a clue as to wassup with a lot of issues and just replace stuff just because.

The rotating assembly is well worth the $$$$

A 141 Block is not a bad block. Pre squirters and could be a great find.

Check the bottom end for cracks.

Missy
 
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