The Ford Barn

700rpm · 06-06-2015, 03:11 PM

40: no signs of a loose sleeve.
Paul: Yes, all bearing clearances have been checked and are proper.
Wilbur: wrist pins are loose.

40 Deluxe · 06-06-2015, 03:52 PM

700rpm, rather a sleeve being literally loose, I was thinking more along the line of a sleeve being pressed into a lightly undersized bore and thus on the verge of collapsing inward. Then, with the normal expansion at operating temperature, it 'moves' inward just enough to pinch the piston. Or maybe something odd with the sleeve material itself or the way it was cast, allowing a dimension change when it warms up. At any rate, you have something unusual going on here, so you have to think outside the box.

40 Deluxe · 06-06-2015, 04:04 PM

Hare-brained idea: remove the crank, put the head on and torque to specs. Likewise the main caps. Turn the block upside down and measure the bores with a precision bore gauge. Then run hot water through the block and measure again(in multiple places). With only the top part of the cylinders covered by the water jacket, there's more of a chance of uneven expansion, as I mentioned in my previous post.

Synchro909 · 06-08-2015, 02:57 AM

This is a long shot and unlikely but how is the end float on the crank shaft?
Starting to look for a hair in an egg yolk here!

700rpm · 06-08-2015, 09:37 AM

Thank you all for your suggestions. I'm in the middle of building a deck, so no Model A work is getting done, at least for the next two weeks. I'll be back when I've tried some of these ideas.

06-06-2015, 03:11 PM	#21
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 5,903	Re: Update on ring clearances 40: no signs of a loose sleeve. Paul: Yes, all bearing clearances have been checked and are proper. Wilbur: wrist pins are loose. __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.

06-06-2015, 03:52 PM	#22
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,779	Re: Update on ring clearances 700rpm, rather a sleeve being literally loose, I was thinking more along the line of a sleeve being pressed into a lightly undersized bore and thus on the verge of collapsing inward. Then, with the normal expansion at operating temperature, it 'moves' inward just enough to pinch the piston. Or maybe something odd with the sleeve material itself or the way it was cast, allowing a dimension change when it warms up. At any rate, you have something unusual going on here, so you have to think outside the box.

06-06-2015, 04:04 PM	#23
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,779	Re: Update on ring clearances Hare-brained idea: remove the crank, put the head on and torque to specs. Likewise the main caps. Turn the block upside down and measure the bores with a precision bore gauge. Then run hot water through the block and measure again(in multiple places). With only the top part of the cylinders covered by the water jacket, there's more of a chance of uneven expansion, as I mentioned in my previous post.

06-08-2015, 02:57 AM	#24
Synchro909 Senior Member Join Date: Jun 2014 Location: Melbourne, Australia Posts: 7,496	Re: Update on ring clearances This is a long shot and unlikely but how is the end float on the crank shaft? Starting to look for a hair in an egg yolk here! __________________ I'm part of the only ever generation with an analogue childhood and a digital adulthood.

06-08-2015, 09:37 AM	#25
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 5,903	Re: Update on ring clearances Thank you all for your suggestions. I'm in the middle of building a deck, so no Model A work is getting done, at least for the next two weeks. I'll be back when I've tried some of these ideas. __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.