I have a 105 (mirror) block.
I would like to see if it will take the 4.13" bore.
I gather it needs to be sonic checked.
What is the actual number they are looking for?
How thin is too thin?
I imagine it depends on who you take it to...but what is the general consensus?
I don't want the walls so thin I have cooling problems.

 

a fe with .080 overbore will run warm no matter what!

 

The mirror 105 castings SHOULD take the .080" overbore and work just fine. However, that's definately NOT what I would do. Just take it over enough to clean it up. Usually that's .030". The only reason to bore it over so much is to use bigger valves; if you're not doing that there is absolutely no reason. I suppose if you wanted to say you have a 406... Of course no one would know anyway once the motor is assembled.

 

Bare with me, I am trying to understand this.

I had read earlier that the 105 mirror block was a 428 service replacement casting. If that is so, then taking it to 4.13" bore shouldn't act (overheat)like an .080" overbore, because that's what the 428's were?

Hence the question on wall thickness.

As far as rebuilding the motor, I should have been more specific, I would like to build it as a 428.

 

Technically, this SHOULD be true. If it is indeed a 428 casting, the cylinder walls SHOULD be thick enough that at 428 dimensions the wall thickness would be about factory. Notice I said SHOULD. It is possible they reduced the OD of the cylinder wall for the block when they modified the 428 molds for 390 specs. I think all they'd have to do is bore the cylinder sleeve area in the block smaller and use the standard 390 cylinder sleeves (dont think normal cylinder sleeve, think stock cylinder wall in block). To tell for sure, you still need to have it checked.

 

Are all blocks sleeved or is the piston bore part of the casting?

I guess it is also possible that Ford ultrasonic tests the block cylinder walls for thickness (as cast), and decides which ones can be made into 428's and which made into 390's?

 

The bores are steel and the block cast is Iron...the Bores are cast into the block..