Piston Markings

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Model T Ford Forum: Forum 2012: Piston Markings
Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gregory on Thursday, December 20, 2012 - 07:10 pm:

Just pulled the head from my 1919 Touring. If the engine has been bored sometime in its past 93yrs would the tops of the piston be marked as such ? These are cast iron and have no markings..standard bore ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Thursday, December 20, 2012 - 07:16 pm:

throw a caliper on your bore and sweep it back and forth and the largest reading will be pretty darn close.

yes most cast iron pistons ive seen are marked with an over size. have you cleaned the tops thoroughly? it could be easy to miss the marking.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gregory on Thursday, December 20, 2012 - 07:21 pm:

Yeap...cleaned them but couldn't see anything but 2 little punch marks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By joe bell on Thursday, December 20, 2012 - 07:30 pm:

the punch marks, from what I was told are the weights that the piston and rod weighs, there was four weight groups, I first thought they where stamped 1-4 for the cylinders they where in but the punches where the same on every piston?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gregory on Thursday, December 20, 2012 - 07:43 pm:

Yes..these are all the same


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Friday, December 21, 2012 - 12:26 am:

Joe Bell covered it. Weight groups for rough balance from the factory.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Friday, December 21, 2012 - 09:58 am:

And if you really look for it, the original Ford iron pistons are always stamped 'Standard' to indicate factory bore size.

Many times you can't see the stamping, old crust of carbon, or gouges from years of chisels scrapping off carbon :-)

Highlighted the STANDARD marking with chalk.







And Ford oversize iron pistons are likewise stamped, but no dots, as these later pistons were placed in the motor outside the factory, so no factory assembly weight dots.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gregory on Friday, December 21, 2012 - 07:58 pm:

So what i may have are standard Ford pistons...WOW ! after 93 yrs you would think it would have been bord at least once ! Pulled one of the rod caps tonight...babbit looks good but no brass shims. I've got a long way to go !


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Friday, December 21, 2012 - 11:14 pm:

I don't know about Eastern states, but in Califunny, I have owned nearly two dozen original T blocks over the past forty years. Only two had ever been bored oversize, and only two others so far have been worn enough to require being bored out.
Drive carefully, and do enjoy the holidays! W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Woods, Katy, Texas on Friday, December 21, 2012 - 11:57 pm:

I noticed in one of Dan"s photos that one piston was stamped .025 OS. The motor in my grandfather's 27 coupe had .031 OS pistons and we had to rebore to .040. Does anyone know how many factory OS pistons Ford made. I know they made .040 OS, also. Why would they make a non increment of 5 or 10 piston (.031)?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren (Australia) on Saturday, December 22, 2012 - 12:20 am:

Terry, that's old skool stuff, if an engine had one crook bore that's what was fixed, cleaned up the pot and fit a matching slug to it, some times even turning the piston to fit. Same as bearing journals, only grind the ones that are out of spec.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska, Denver CO on Saturday, December 22, 2012 - 12:30 am:

Terry,

It would seem that Ford supplied replacement pistons in fractional measurements as a .031 oversize piston would be 1/32 OS.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Gregory on Saturday, December 22, 2012 - 07:54 am:

Thanks Wayne...if I'm lucky I won't need to bore this block.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Saturday, December 22, 2012 - 08:11 pm:

Actually that is 0.0025 oversize. Legend has it a lot of oversizes were available.


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