Broken Piston

lafarm

lafarm

Member
I used to be on the old Ford Barn but this is my first post on this one.
My 30 coupe has been running real good but I imagined I could hear a slight noise I didn't like so I thought I would drop the pan and check the main and rod clearances, Surprise! Bunch of broken aluminum in the pan pulled out the broken piston everything else looks good no visible wear on cylinder piston or Babbitt was wondering if this could be caused by piston hitting head gasket as piston top comes slightly above block deck? Also was wondering if any of the parts suppliers sell just one piston and ring set? The catalogs I have just sell sets. Thank you to anyone that can give me a clue why this happened and prevent it from happening again. attempting to add image ??
Gordy
piston.jpg
 
Whats the piston size on top say? Some one may have some spares to give you! Cause?????Did you find the pieces in the Pan? Just reread, parts in pan.
 
Would like to see the top of the piston to see if there is any indication of it hitting something. Check the head gasket for any signs of ANY of the pistons hitting it. Also check all the pistons skirts for any signs of cracking or damage. You need to find the cause of this damage before it's put back together.
 
Tom. I can not see any sign on the piston top or head gasket where there was any interference can not see any cracks in the other pistons
 
JB weld them back together.:cool:

I don't think I would just replace one piston. Different style, weight, etc would only cause additional problems in my opinion.
 
Could detonation be the cause? Perhaps lugging the enigne with the spark lever down? Timing somehow not set right? Overheating with hot spot in that cylinder? Worn distributor shaft/lobe/gear?
Engine assembler drop the piston/rod assembly? I've done that; the piston hits the floor and the rod swings on the pin with enough force to bend or crack the piston skirt!
 
Just saw the post about not replacing just one piston because of possible differences. This can be worked around quite easily. Connect the new piston to the old one with a wrist pin and compare heights, ring grooves, etc. Mike both diameters or check in the bore with a feeler gauge. If you have all the broken pieces, weigh them with the piston and compare to the new one. If you don't have access to an accurate scale and if your post office lobby has a self-serve unit, weigh the pistons there. Those scales go to tenths or hundredths of an ounce if I remember.
 
The biggest thing I see with that piston is it appears to be a split skirt piston. They are not a strong piston to start with due to their design, --nor due to their age.

While an interference issue is a possibility, I have seen similar situations as a kid growing up in the Model A club where hobbyists would buy flea market pistons that no one had a clue about the history or the handling care they received prior to purchase. For example, maybe these were dropped off of the Western Auto store shelf back in the 40's and restuffed back in the box yet the unseen damage had been done. Backyard rebuilders may have not known what to look for when doing the assembly and due to the harmonics we push our engines into today, that exacerbated the hidden damage and turns it into something like this. Maybe the machinist dropped it while floating the pins? Maybe it was a cheaply manufactured piston to start with. Who knows??

The bottom line IMO is what your plans are for the future. If they are to drive in local parades or around the neighborhood at slow speeds, then one 60-over replacement piston can be installed (even a used one) and it is unlikely you will ever notice a problem again out of that hole, ...or any of the other three. If your driving style calls for more severe plans, then IMHO your repair plans need to be more severe too. At that point, a minimum you should be considering is replacing all four pistons & rings onto your existing rods, ...or maybe a complete disassembly with the plans to true-up the cylinders by boring the block .080 and installing modern cam-ground pistons and quality rings. Power in a Model A engine is directly proportionate to compression, and rings need to be able to seal well against the walls. Good luck, ...and if I were in your shoes I wouldn't look back with worry, and just strongly consider any of the three options I mentioned depending on my driving style.

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I normally drive it around 500 miles a year so I have decided to install a new set of pistons and rings, May be able to go to the parades on memorial day if I get to work.
 
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