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4.0 block question


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i tore down a donor block today and noticed a hole that iam not sure of...

iam thinking this may be a hole that the oil can come through for the timing chain and all iam not real sure so i figured id ask someone on here

 

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what am i lookin at in the second picture? whats wrong? (i've never torn down an engine)

 

first pic. note the jagged hole above the camshaft hole

 

second post's pic.

 

note that hole isn't there.

 

that's the problem...it SHOUDLN'T be there. hence need for new block.

 

In all reality, I think you could fix that...

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Just because a block is cracked or missing a chunk doesn't mean it is scrap. Since it isn't a load bearing surface which doesn't require machining what you have there is easily repaired. Simply prep it and braze a filler piece in place. I would use a piece of 1/4" steel with heavily beveled edges so as to provided a larger face area for the brazing to grab hold. This makes for a stronger repair especially since you are only able to get to one side.

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ok.. either i have HORRIBLE LUCK... or this hole is supposed to be there... i just picked up this block yesterday tore it down today and to my great anger and suprise that same hole is there in the same damn spot...

 

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now i think it has to be there for a purpose...and that purpose has to be to lube the timing chain the timing chain cover is sealed against the block and the oil pan so that has to be the reason for the hole... so i just wasted more money.. anyone need a 4.0 block?

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think i answered my own question... looks like i need another block

 

CamIn.jpg

 

well in that pic above.. you can't see a hole only because i think the angle at which the picture was taken makes it to where you can't see the hole.. now that i have 2 4.0 blocks iam guessin this is a lubrication hole for the timing chain..

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88swampedmj,

This is a picture of my 1989 block out of an MJ that I am going to build a stroker out of -

Hole there, but smaller. They may have enlarged the hole for better lubrication? :dunno: Hope that helps, Rich

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oh thanks for the help... i guess ill go forth with this build... using the best block i just got a little worried seein that hole in both haha... but it makes the most sence that it would be a lubrication hole.. thanks for the help again

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Watson I believe when they cast the block they get a thin spot of casting flash there. The same sort of casting flash you would get with plastic boyhood models, which often had thin flash filling area's that were supposed to be holes. Then the factory would punch the hole out afterward, due to core shift sometimes the punch removes a nice neat rectangle, and sometimes the hole looks like someone blew up something. :smart:

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That hole is suposed to be there. I have torn down and built lots of Jeep 4.0L motors and every single one had that there. Its to let oil down into the timing chain. I removed the flashing from the casting and opened up the hole and my motor is still running strong. I also opened up and cleaned out the block flashing in the head and block so that oil drains back down from the top of the head into the oil pan. The stroker motor in my Cherokee works great and I have had absolutly no issues with it.

 

AARON

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