What is the maximum 440 over-bore size?

[Dave22443]

What is the maximum you can safely bore out a 440 block?

[Mike DC]

I think it's .060 on any block, and maybe .080 on a good block that passes sonic checks. 

But I'm not 100% sure off the top of my head so don't take that as gospel.

[Rolling_Thunder]

.060"

[firefighter3931]

The general rule of thumb is .060 but some can go bigger.....just depends on the cylinder wall thickness. On the flip side ; some can't go .060 due to core shift and thin walls so it allways pays to have the block sonic checked to see what you've got before spending all that $$$ on machining costs. 



Ron

[Dave22443]

Thanks for the input guys.

Reason I asked is because my block is in the shop now.  Its got some rust issues and they are trying to clean it out.  I had authorized them to go uo to .040 over, but after doing that, they say it will need to go .060.  I'm nervouse about going .060 and wasn't sure I even could (or if it was advised or not) without hitting water. 

I've never heard of a sonic test.  I'll have to ask them if they can do one.

[firefighter3931]

Dave, the sonic test is basicly a soundwave thing where they can measure the cylinder wall integrity. A probe is dragged along the cylinder wall and readings are provided.The most important measurement is on the major thrust side where the block recieves most of it's stress. For reference...this is the passenger side of the cylinders on both banks. I would have it checked before throwing any more money into the machinework. 

If any part of the cylinder is less than .100 (after the .060 bore) then it's questionable. I like to see at least .120 on the major thrust side...as a minimum. (after overbore)



Ron

[Mike DC]

Good info there, firefighter.