Question for machine shop guys

[miller]

Setting up my 69 440 Magnum for rebuild.

Question is, from your experiance, on boring the block, how much is the least amount needed to clean up the holes. Yes, I understand it's a hard thing to answer.

Measured up when I broke the motor down. Off the top of my head, recall .008 over standard, at only one location in one hole. Think the others averaged 5-6 wear. That's all at the main wear areas in the bores.

Am I expecting too much, for it to clean up at .020 over?? (Bought pistons years ago.)

Thanks for any thoughts.

 

[Dako]

If the worst is .008, theoretically it should 'be round' again at .010. With that said, they could continue up to the .020 over pistons you bought years ago. If it turns out that you have a hole over .010 they would be going to the .020 anyway.

 

[69Bee]

The first oversize now in Sealed Power pistons is 0.030"OS. If you already have 0.020"OS pistons, ask the shop to try for that first. The biggest issue is when they bore it. The old rule of thumb was to center the boring bar in the bottom where the cylinder is worn the least, or not at all. I have found that that method could make you bore more out of the cylinder that you might if you were to center about 1.5" down from the top. You center in the worn portion, and more accurately center up the new bore with the least amount of metal removed.

On another note, how is the condition of the pistons you have? If they have been kept clean, and stored properly, you should have no problems. If they are questionable, I would just go 0.030", and be done with it.

 

[Meep-Meep]

On a V8 with normal wear and an .008" ridge then it should clean up at .020" over. Some sixes, like the Ford 300 CI is deceiving because the first cylinder is looking right at the water pump and the front half of the cylinder cools better than the rest of the block. The result can be some interesting wear patterns that will take at least .030" to clean up (out of round issue). If your block has water damage the pitting from rust may not even clean up completely at .030", so take a good look at it. FYI: I have honed and reringed up to .008" on non rusty cylinders with excellent results.

 

[miller]

Thanks, guys!

Pistons have never been out of the box, same as the day I bought them, brand new. KB237 +020.

Engine has never been touched, except me busting it down.
Yeah, understand all the sizing stuff. Also need to pick a good day to re-measure things, since those KB237s want a certain clearance.

Just been too long. All my machine shop buddies are like me, lost in the dust, from years ago, and talking with some of the local shops hasn't been too exciting.

My way of thinking, there should be enough meat there to cut, but I don't have much hope of finding anyone who would let me 'borrow' their machine. So, I'm stuck depending on someone else's hands.

- - - Updated - - -

On a V8 with normal wear and an .008" ridge then it should clean up at .020" over. Some sixes, like the Ford 300 CI is deceiving because the first cylinder is looking right at the water pump and the front half of the cylinder cools better than the rest of the block. The result can be some interesting wear patterns that will take at least .030" to clean up (out of round issue). If your block has water damage the pitting from rust may not even clean up completely at .030", so take a good look at it. FYI: I have honed and reringed up to .008" on non rusty cylinders with excellent results.

Thanks for that, Meep-Meep!

Thought I was getting out of sorts. A little unsettling though, when I've discribed what I have/what I want...and I get a crooked head look, like I'm a little nuts.

Just know what my temperment would be, if some 'we'll hog it out for ya' shop screwed up my block.