.060 overbore on '69 400

[Phil69GTO]

Found out that my block needs to go .060 over. What do you guys think about a sonic check for a street application with this block??

[Phil69GTO]

Found out that my block needs to go .060 over. What do you guys think about a sonic check for a street application with this block??

[Old Man Taylor]

It is a tough call. Since it will be apart, it would be good insurance to sonic test it. However, this vintage 400 will usually take a 0.060 overbore OK. I did it to a '68 400 with no problems.

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Jim

[Dick Duclow]

At .060 cylinder distortion (and hence, cooling) become a concern. We ALWAYS fill the bottom of the block (up to the lower edge of the freeze plugs) on .060 over engines that will see street use. It's just cheap insurance. We have had equal sucess with Hard Blok and Moroso Block Filler.

[PONTIAC DUDE]

DITTO

[AG]

How does cylinder distortion affect cooling?

[PONTIAC DUDE]

Increased friction from uneven cylinders. If,say you have .004 wall clearance and it distorts to,say .006 from compression firing. this buids heat. Piston rock, wall load on firing, normal swelling, etc, all contribute to friction & you try to control this as best as possible. Later.

[Paul Spotts]

I recommend the hard blok over the morosso block fill.

[Steve C.]

Good info about filling the block. We have always used a torque plate for better ring seal during honing, but could this apply here when condidering boring .060" over? I have heard some say use the plate during both the boring and the honing. Some say during the hone only is necessary.