.010 over pistons Question

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Model T Ford Forum: Forum 2016: .010 over pistons Question
Top of pagePrevious messageNext messageBottom of page Link to this message  By lorenzo leon on Friday, November 18, 2016 - 10:56 pm:

where can i find .010 over pistons for a 26 T block,i cant find them in the books
Thank you..


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Saturday, November 19, 2016 - 02:23 am:

1990's vendor parts books don't even list them, haven't been around for a long time, I would think that they are not available because a STD bore wouldn't clean up at .010"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Saturday, November 19, 2016 - 04:25 am:

Sometimes, you can get cast iron pistons in .010 over. A ridged hone can clean up a slightly worn bore enough to make them fit.
But of course if you want to consider cast iron pistons? That opens a whole new can-o-worms. I have run cast iron pistons in several Ts with excellent results. But they do have some downsides. Higher speeds added stresses to crank shaft and bearings is a solid consideration. A lot of people are strongly against the idea of running cast iron pistons. But I kind of like them.

Usually, a .020 oversize piston can be ground down to a .010. Any good engine shop should be able to do it fairly cheap. And if you are like me, and want to remove as little cylinder metal as you have to to get it to run right and long? Leave enough material so the block can be rebuilt again a couple more times.

Ring fitting is another issue. Standard size rings should probably work okay for a .010 over. Some of the rings I have used recently had much too little gap to run without binding as soon as the engine begins to warm up (ran into that problem once, not fun). The too little gap had to be ground back to fit a standard bore, but was almost a perfect fit in the .010 oversize.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By lorenzo leon on Saturday, November 19, 2016 - 08:25 am:

Can pistons for other cars be used ?
I had the engine rebored to 10 over ,did not know there was no such a piston ,I have a set of iron pistons.015 over I might have to go with
Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Blake, Kansas City on Saturday, November 19, 2016 - 08:57 am:

Leon,

I'm not posting this to criticize but rather so all can learn from your experience.

I'm surprised a shop would undertake to bore an engine without having the set of pistons you intend to run in that engine before they start the operation. As Wayne pointed out you can use a rigid hone to take a standard bore out to .010 over as the setup for boring is pretty challenging if there is any wear in the cylinder. Important distinction between a "rigid" hone and a glazebreaker; A glazebreaker has stones very similar to those used in a rigid hone but those stones are spring loaded and pivot in the middle to allow them to follow a less than perfect bore. A rigid hone moves the stones out by geared racks and will keep the stones parallel to the bore. You can in fact use a rigid hone to straighten out the bore of a worn cylinder to some degree. This depends on the skill and experience of the person doing the honing. And that only works if you have a set of larger pistons to use.

In your case if you have some .015 over pistons have a shop hone your block out using a rigid hone to fit those. Then get some .020 rings and fit the gaps of those to the .015 bore.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Blake, Kansas City on Saturday, November 19, 2016 - 09:22 am:

To elaborate some more. As a general rule, when planning an engine out overhaul, after you disassemble the engine, you should take the bare block to the shop you intend to have bore the engine. They will check the existing bore for wear and any possible damage. THEN you chose the piston size that will allow the bore to "clean up" when boring and honing is complete. And of course, before going to the expense of boring you'll want to have the block checked for cracks and if repairable have that done before you start.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Saturday, November 19, 2016 - 08:10 pm:

It's certainly easy enough to turn the cast iron pistons to work in the .010" block assuming they aren't cam ground.
Don't forget to step the lands!


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Sullivan on Sunday, November 20, 2016 - 01:41 pm:

Even if they are cam ground, no big deal, just gotta find a shop. Dave in Bellingham,WA


Top of pagePrevious messageNext messageBottom of page Link to this message  By J and M Machine Co Inc on Monday, November 21, 2016 - 08:06 am:

People are assuming alot.
Most shops won't even touch a job that the pistons have to be machined.
Nevermind having a machine to machine pistons.
The cost to machine pistons VS replacement set of proper size is right way to proceed.
Telling someone to run glaze buster to get proper size is a longshot and the amount of time doing so could be spent on having a good machine shop do it right.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Blake, Kansas City on Monday, November 21, 2016 - 09:19 am:

Please re-read my post. I did NOT tell anyone to "run a glaze buster to get the proper size". In fact I described the functional difference between a glaze breaker and a rigid hone.

A glaze breaker is just that. Used to prepare the "glazed" cylinder for proper break-in when all that is needed is new rings on the original pistons. That of course is all dependent on whether or not the bore and the pistons one is contemplating re-using are within the "factory" recommended wear limits.

The rigid hone I described is what is used to achieve the final sizing and finish of the bore when new pistons are being used. When I used to bore cylinders we set the cutting tool in the boring bar to about .0015 (one and a half thou) smaller than the desired final size. Then we took that last .0015 using a rigid hone (we used a Sunnen hone). Again, the stones are kept parallel to the bore and the hone is capable of applying much greater pressure when honing to bring the bores to the finished size quickly. The final .0015 removed by the rigid hone is sufficient to remove the tool marks left by the boring bar and of course done using a cross hatch to ensure proper ring seating.


Top of pagePrevious messageNext messageBottom of page Link to this message  By J and M Machine Co Inc on Monday, November 21, 2016 - 09:41 am:

Gary:
You explained it correctly, unfortunately the original poster has gone to a shop that knows nothing about Model T.

We'll get a call and people and will mention" Well I saw it mentioned in the forum why can't you do it"?
"We tried it with the glaze buster or we rented a hone from local auto parts store can you measure this? Why don't pistons fit.?"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Blake, Kansas City on Monday, November 21, 2016 - 10:36 am:

Ah, Thank you for clarifying your comment:-)

The kind of mis-information you are referring to is what I was hoping to help with. I learn a lot from this forum as it has so many knowledgeable people. So I just want to return the favor from time to time.


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