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Old 09-07-2020, 08:09 AM   #1
1crosscut
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Default Fumbled a piston

Well since there wasn't much for football on last Saturday I sort did some on my own...

I am in the process of pulling apart a 1936 Model A diamond block engine. The bore is still standard and I would like to reuse the pistons if everything checks out. The problem is that I managed to fumble one of the pistons and it fell against my engine stand taking a couple of small pieces out of the skirt. Would using a piston with this type of a defect be troublesome?
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Old 09-07-2020, 08:17 AM   #2
Bob Bidonde
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Default Re: Fumbled a piston

I would use that fumbled piston. I have used worse than that one without issues.
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Old 09-07-2020, 08:19 AM   #3
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Default Re: Fumbled a piston

I don't think I would, I'd think you'd have to remove the same amount of metal from the other 3?? New pistons/rings shouldn't be that expensive. JMO I'm sure "back in the day" a fix like that was common.
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Old 09-07-2020, 09:09 AM   #4
Jack Shaft
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Default Re: Fumbled a piston

Why do all that work and always wonder about that one piston? you can see where it broke,but you cant see how much its fractured.

New solid skirt pistons are 95 bucks a set..
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Old 09-07-2020, 10:36 AM   #5
Jim Brierley
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Default Re: Fumbled a piston

I think it is good enough to use. The damage is not on the thrust side, and is small enough that it shouldn't cause imbalance.
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Old 09-07-2020, 10:42 AM   #6
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Quote:
Originally Posted by Jack Shaft View Post
Why do all that work and always wonder about that one piston? you can see where it broke,but you cant see how much its fractured.

New solid skirt pistons are 95 bucks a set..
That was my thinking. Also, I would check the piston/wall clearance while you are there and if it's getting a bit sloppy and/or the cylinders are tapered, go .030 over. Price of the pistons is the same and I don't think it would cost much to bore 4 cylinders
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Old 09-07-2020, 11:01 AM   #7
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Default Re: Fumbled a piston

That's the whole thing,cost and frame of reference.Run a chipped piston? yeah why not,when engines were five bucks and plentiful it made sense. Today,with today's prices for machine work and parts it doesn't make sense to take a chance.Not to mention the added value some folks put on subcontractor castings,the 'diamond' factor. Would the piston be okay? likely it will,but for 95 bucks and the rings you would buy anyway why risk having to tear it down again?
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Old 09-07-2020, 11:28 AM   #8
Kurt in NJ
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Default Re: Fumbled a piston

is it centerlock, or end clips for the wrist pin
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Old 09-07-2020, 12:00 PM   #9
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Default Re: Fumbled a piston

Purely a budget and personality decision. It would be just fine. Now the question whether you would be fine whichever way you go?????????
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Old 09-07-2020, 12:47 PM   #10
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Default Re: Fumbled a piston

If you decide to reuse it I would use a rotary file and smooth up that area, and on the other side, and 3 more times making all the Pistons look factory !
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Old 09-07-2020, 02:00 PM   #11
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Default Re: Fumbled a piston

I would not put a damaged piston back in an engine. Too much risk. New pistons are less than $100.00 perv set. Even that much hicki on the piston can cause an imbalance and somewhere down the road you will be say "I wish I had???". I balance my pistons and rods to within less than 1 gram of each other. Necessary, No. Satisfaction, Yes. ken
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Old 09-07-2020, 03:04 PM   #12
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Default Re: Fumbled a piston

use them only if you can’t afford new ones!
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Old 09-07-2020, 03:30 PM   #13
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Default Re: Fumbled a piston

Guten Abend Dave.

If it were my engine, which I would drive a lot in my car in the future, I would take four new oversized pistons and with cylinderliners grinded and honed.

Yes, the piston can still be used. But it imbalances a little. And with every trip you would crawl your ears into the engine to hear if something knocks. Four complete cylinder sets are an increase in value for 100,000 miles without uncertainty.
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Old 09-07-2020, 06:54 PM   #14
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Default Re: Fumbled a piston

Thanks for all of the advice.
I have two of the industrial / binder engine power units. Between the two I should have enough parts and pieces to make one complete unit to use as a running display. I have yet to open up the second engine to see what condition it is in but I think it is probably the better one of the two. If both end up being run able I would put the "weakest" engine into the display unit.

This engine does't have any more shims left on the rods for adjustment but the babbit is good on all four and the clearance on all four is spot on at .0015
Rear main babbit looks good, has .0015 clearance and still has a few shims.
Crank shaft end play is .007

I haven't opened up the front and center mains yet. Fingers crossed.

Original style non adjustable valves and the clearances on those are all over the place so that will have to be put right.

Since this would be an engine that is not really going to be put under a load running the piston as is might be an option. I always weigh and balance pistons so I'd have to check to make sure the weight could be made right.

If I do end up going with new pistons I'm sure I'd be looking really hard at the possibility of having it bored to the next size over.
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Old 09-07-2020, 09:49 PM   #15
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Default Re: Fumbled a piston

If it is just for running display I would use the piston after checking it over carefully and doing as Big hammer suggests. It will be easy on it since it won't be under load or speed.
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Old 09-07-2020, 10:41 PM   #16
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Default Re: Fumbled a piston

After the work of tearing it down and wondering if you would want to go thru the work of putting on a new head gasket cleaning of the head and block mating surfaces and all the other work involved including replacing the pan, wouldn't it make sense to check the cylinder bores for surface, size, and taper and possibly install new pistons IF still standard bore, new rings and the other paid to attention details?
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Old 09-08-2020, 01:00 AM   #17
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Default Fumbled a piston

1crosscut,

I believe that l might be able to help you out with that piston, l have a STD bore '32 engine that l had a rod go out on years ago and l have modern STD pistons and will get replacement rods when l put it back together. This leaves a set of or a single original Ford Script piston that you may have, l will have to locate them.

These pistons us the Center lock, not the modern clips on the ends of the piston pin.

I am currently in Healy Alaska, 120 miles south of home, travelling to Wasilla in the morning to pick up some new Lester tires for the Phaeton that l am driving.

Darryl in Fairbanks
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Old 09-08-2020, 07:55 AM   #18
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Default Re: Fumbled a piston

I run a couple of Diamond B engines, still on stock bores with the original pistons. I'd just smooth that chunk out, and take the same out of the others till the weights match...
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Old 09-08-2020, 09:46 AM   #19
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Default Re: Fumbled a piston

I have a set of standard nos pistons that have some storage wear that you can have?
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Old 09-08-2020, 08:25 PM   #20
1crosscut
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Default Re: Fumbled a piston

Todd and Darryl those are very generous offers and I really appreciate them. Once I get the other two mains looked at and some measurements on the cylinders I will have a better idea on what direction is going to be best to go and will reach out to you.
The pistons are center locks.
Tomorrow I am having my left knee scoped to repair the meniscus. It's probably going to limit my fun time in the shop for a few days so progress may slow a bit.
Darryl if your driving the Phaeton to get your tires I hope you are having better weather than we are having here. 44 degrees with rain and wind. Big change from the 90's we were having over the weekend. Not complaining though as we need the rain.
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