[Dauntless1971]

I am considering using .005 oversize pistons on a block that appears to have very little wear on the cylinder walls. I have a dial bore indicator gauge, but l am not a machinist. Best I can tell the cylinder appears to be right at that measurement now. And forged pistons require 4 to 5 thousands clearance which can be done with honing?

[Dragncar]

You could hard block it. That requires a extra .002.
extra ring gap too.

[PAUL K]

Yes you can hone the cylinders for 4.125 pistons. It might not be enough to make the cylinder round with a torque plate.

[Jack Gifford]

I had no problem running 4 1/8" pistons in my blown alky mini-puller, using a '67 400 block honed to 4.125". Turned 8,300 RPM on most runs. I heard a lot of "Didn't know Pontiac made a 401".

[Dauntless1971]

Originally Posted by Dragncar

You could hard block it. That requires a extra .002.
extra ring gap too.

Is this filling the water jackets?

[Tim Corcoran]

Originally Posted by Dragncar

You could hard block it. That requires a extra .002.
extra ring gap too.

This is interesting, does filling the block add heat to the top of the piston?

[Dragncar]

Originally Posted by Dauntless1971

Is this filling the water jackets?

Yes, filling them to the bottom of the water pump holes.
If you do it, get it done before you hone the block and its best to let it cure with a head-tq plate torqued down.

[Dragncar]

Originally Posted by Tim Corcoran

This is interesting, does filling the block add heat to the top of the piston?

Yes, both Ross say to add .002 piston to wall, and Total Seal said to add .002 ring gap.
So I have .006 piston to wall and around .023 end gap.
Thing is, Dan said I might hear the pistons before it warms up but it sounds normal. And AWESOME too I might add.
Taking a day off today to get a 4 day weekend to work on my car.

Finish fuel pump, fuel cell install.
Finish new smaller brake booster and proportioning valve install along with a auxiliary vacuum pump for the brakes.
Put my PTC converter back in.
Install new 1350 front yoke.
And re install my headers I just got back from being coated. That will be a chore getting them in without scratching (700$ to coat) Think I will wrap them in blue painters tape first then take off.
And if I get around to it put in a Fantz by pass filter to go along with my K&P wire mesh oil filter. Made a fuel pump cover with 1/4" nipple to get the oil back in.

My old 455 I ran forever. Its .060 and I am planning on hard blocking it and running a .065 over piston and ridged hone with plate.
The extra .002 might be useful for me and might help the OPs situation too.