Cracked Piston

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Model T Ford Forum: Forum 2016: Cracked Piston
Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Monday, October 10, 2016 - 05:26 pm:

Not a good day! Yesterday I had a nice drive of about 10 miles or so and put her to bed. She was running great. This morning I went to start her and there was a TERRIBLE sound that sounded like a metal part breaking (this was on the first rotation). She did not start and I immediately stopped. I pulled the pan and all the rods and caps are fine (I had just worked on these and as a newbee was quite pleased with myself – so much for that! ). So I pulled the head and low and behold there is a cracked #1 piston. I pulled the piston and a piece of it fell off in my hand. Like I said – bad day! I am so glad I stopped when I did because there does not appear to be any damage to the cylinder – smooth as a baby’s behind. The rod and all it’s parts appear fine as well. These are aluminum pistons .04. I do not know when the engine was rebuilt nor the miles since rebuild. I have read some other forums and they say it is Okay to replace the single piston if all are “common” (I don’t see this question on MTFCA…) So - Two questions – 1) Has anyone done this (replace a single piston with a match)? And 2) any idea how or why this could have happened? There was a little carbon on top – but not enough to fret… I really do not want to pull the engine if avoidable – but will if that is the advice. Thanks all - I feel bad...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, October 10, 2016 - 05:55 pm:

You can replace a single piston if the bore is not out of limits. You need to measure the bore size - accurately - top, center and bottom on two axis if using a micrometer, or on one axis if using a dial bore gauge.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Monday, October 10, 2016 - 06:07 pm:

Peter. I have 3 pistons, .040 over, left from when I replaced one which had galled a few years ago. Got them from Langs. I'll sell them cheap.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 10, 2016 - 06:20 pm:

I feel it is critical to try to establish WHY it happened. There is limited percentage in replacing the piston without knowing this.
Is there any evidence that the piston hit the head?
Is there a "ridge" at the top of the ring travel area of the cylinder?
Does the wrist pin move freely in the piston?
While you were adjusting the rods is it remotely possible that the piston got jammed up against the cylinder head?
I'm just trying to think of possibles!! There are probably others
If you were just adjusting the rods, then likely there will be some wear in the cylinders so most .040 pistons should just slide in. Always good to check clearance though. I consider.005" to be a minimum and I would be OK with.010" on your used engine at this stage. A easy check is to hang the piston in the cylinder upside down and check the "skirt" clearance at 90 degrees to pin (I would prefer to have the pin oriented in line with the crank) with a feeler gauge
Some pictures would help us to help you


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Monday, October 10, 2016 - 06:29 pm:

Dave - I sent a PM.. Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Monday, October 10, 2016 - 06:29 pm:

Royce - thanks for confirming! I was hoping this could be done!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Monday, October 10, 2016 - 06:36 pm:

Les - I agree cause is a big deal! I am so lucky there was no additional damage. The #1 rod bearing snug up went smoothly following advice from you all. It was a simple shim removal - all the babitt was excellent - I was pleased if not surprised how snug everything was. The piston slid right out -- Wrist is free etc.. Strange.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, October 10, 2016 - 07:44 pm:

The cause IS a concern. Unfortunately, there may not be a nice option. Not knowing when the engine was rebuilt puts you at a disadvantage.
About twenty to thirty years ago, some pistons made for model Ts were found to not be reliable. A lot of people had one or two out a set broke for no apparent reasons. I understand that the manufacturer corrected some issue believed to be responsible. But I figure that there are many hundreds of those pistons still in use.
There are a number of other possible causes, such as improper fitting when assembled? Possible damage or other defect in the piston? Close examination may or may not reveal the cause.
Changing a single piston is not a big problem. But balance could be an issue. If you pull one other piston, and balance the new piston to match it? You should be close enough to be good. But without some comparison, just throwing one new piston is a crap shoot for matching balance. The best thing, would be to replace all four pistons with a new set, check all four for proper fit (I use a feeler gauge between the piston skirts and the cylinder walls both top and bottom of the cylinder, works for me). But, if you cannot afford a full new set, replacing a single would probably work okay. For whatever it is worth, most of those piston breaks were such that usually there was no cylinder damage. So running with "suspect" pistons could lead you to a further adventure, but likely not a disastrous one.
Part of the fun of model Ts is overcoming these things!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Severn - SE Texas on Tuesday, October 11, 2016 - 12:38 am:

Wow Peter. What a welcome home gift. Let me know if you need a hand.

Bill


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Severn - SE Texas on Tuesday, October 11, 2016 - 01:12 am:

Peter,

With no other apparent damage, I would suspect Wayne is right about inferior pistons. I can remember buying a set of aluminum Pistons from Argentina. I had no problems with them, but I think others did.
I agree that the best course of action would be to replace them all. If you replace just one, any of the others might fail at any time.
That's such a cute car, I'd hate to see it break down.

Bill


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Tuesday, October 11, 2016 - 02:44 pm:

Thanks Bill! A welcome home gift indeed! I suspect it was bad as well - the rebuild was likely in that time frame. There were other cracks in it as well... The other three look fine. I took Dave up on his offer (what a great community this is!). I will put the one in and get her going again for now. I may pull them all when time permits as a preventative measure. The good news is I am certainly learning a lot! I appreciate the offer for a hand - and may well take you up on that. Let me see if I can get her goin...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Tuesday, October 11, 2016 - 04:28 pm:

At some point I replaced all the 030 oversize pistons with new. There where no visible sign of wear in the cylinders and no smoking after the swap.
I had issues with one of the pistons and for some reason the upper ring where omitted.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James M. Riedy, Sandusky, Ohio on Tuesday, October 11, 2016 - 09:35 pm:

Peter, I like Wayne S. think it would be best to replace all the pistons but since you have three available I would replace two the bad one and the mate to it. What I mean is since the T crank is basically a two up two down system replace the two that include the bad piston. So when the bad piston is up replace the other piston that is up. That way things are a bit more balanced. I hope I'm making sense to you. Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Tuesday, October 18, 2016 - 07:29 am:

Thanks for all the support and advice! I managed to replace just the single piston for now and she is on the road again. I had to remove all the rod shims to get her tight and it did alleviate the rod knock. As a newbee this was a great adventure and I feel like I am coming up the learning curve. The babbitt was in pretty good shape and the center main appeared tight from what I could tell. I appreciate the advice to replace all four and that is the plan. I just want to enjoy her for awhile! As Humble Oil used to say-Happy Motoring!


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