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4.6L Bore wear. How much is too much?


rich222

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So given the LR overhaul manual doesn't specify a max bore wear figure, just a max ovality of 0.013mm, how much bore ware is too much?

I have one cylinder that's 94.11mm at its widest (side to side) and 94.08mm long ways. So technically out of round and way past the bore size for type B pistons of 94.030mm.

The rest are OK at around 94.05mm.

There is a max bore to piston clearance of 0.045mm, which is also pretty tight.

Am I going to be ok to just flex hone it and put new rings in, or should I get the whole block rebored by 0.1mm and fit oversize pistons?

(I don't really want to go to all the hassle of fitting top hats. The block has the lip at the bottom to stop the liners dropping)

 

 

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Hi, rich222,

Welcome to the forum.  I must admit that I'm a little surprised that you haven't had a response to your question since the forum generally is technically orientated with a vast amount of experience and knowledge.  I'm sorry that I cannot help you myself, having a 300Tdi, and not having any personal experience of rebuilding engines.  At least this response will bounce your query to the top of the subject list and may catch someone's eye.  Best wishes with your rebuild.

Mike

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On 1/27/2022 at 9:42 AM, rich222 said:

So given the LR overhaul manual doesn't specify a max bore wear figure, just a max ovality of 0.013mm, how much bore ware is too much?

I have one cylinder that's 94.11mm at its widest (side to side) and 94.08mm long ways. So technically out of round and way past the bore size for type B pistons of 94.030mm.

The rest are OK at around 94.05mm.

There is a max bore to piston clearance of 0.045mm, which is also pretty tight.

Am I going to be ok to just flex hone it and put new rings in, or should I get the whole block rebored by 0.1mm and fit oversize pistons?

(I don't really want to go to all the hassle of fitting top hats. The block has the lip at the bottom to stop the liners dropping)

 

 

In my experience just flex honing the bore will not remove ovality as the flexible hones will just follow the bore shape, so if your out of tolerance now it's only going to get worse. I would go rebore and oversize pistons, then you know it's right regards Stephen

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