Chrome Bore Out Of Round - Whats Acceptable?...

**FUJIMO** · 01-29-2022, 04:37 PM

...Mic-ing the cylinders top to bottom on a chrome-bore block that has been overheated. what is acceptable tolerance for out of roundness. all chrome-bore brains please advise...

**Dave S** · 01-29-2022, 06:25 PM

Fuggi..... I have a piston cut in Haff.... and a Wedge......Bang them straghit......You can Dooo it

I have seen them out 15........Most get in within 03......I use a cut piston to hold the cut one in place.

**CI STV** · 01-30-2022, 10:33 AM

I see Powers Performance is offering a bore straightener tool now too:
https://www.powerperformanceengineer...r-straightener

**1954bmw** · 01-30-2022, 11:05 AM

Quick question, did you measure with the head torqued or off the motor??? Any chance the bore might straighten up with the head on it, that's why they use torque plates to bore engines???

**Dave Strong** · 01-30-2022, 01:04 PM

Mercury says max .006"

Dave

**Onetime** · 01-30-2022, 07:15 PM

Originally Posted by CI STV

I see Powers Performance is offering a bore straightener tool now too:
https://www.powerperformanceengineer...r-straightener

Jim Ruck made those over twenty years ago!

**FUJIMO** · 01-30-2022, 07:42 PM

...nice piece...

**FUJIMO** · 01-30-2022, 07:43 PM

**Chaz** · 01-30-2022, 10:16 PM

When I made mine I used a piece of all thread for the center bar. Works good, but in hindsight, I wished I used fine thread .. would be easier to turn the nut.

A little oil helps , but we're only talkin a few thousandths .. so turning it one flat is a lot.

**CI STV** · 01-31-2022, 12:23 AM

Originally Posted by Onetime

Jim Ruck made those over twenty years ago!

No doubt. It’s a very simple device that any good machinist could easily make. I don’t see anyone else offering one for sale though…

**Smalltownbassin** · 01-31-2022, 09:47 AM

Originally Posted by CI STV

No doubt. It’s a very simple device that any good machinist could easily make. I don’t see anyone else offering one for sale though…

I just bought one from Jay Smith who has been making them a long time.

**CI STV** · 01-31-2022, 10:56 AM

Originally Posted by Smalltownbassin

I just bought one from Jay Smith who has been making them a long time.

Good to know. Jay is a very knowledgeable guy who has contributed a wealth of valuable insight on this site and elsewhere. Didn’t see one of those listed on his website when I was last on there, but that’s not really a part that the average performance boater would buy anyhow.
Does your tool have a fine or coarse thread? As Chaz has said, using a fine thread would allow for ease of adjustment and I would imagine, better precision.