221 cu in 1939 Failed No4 Piston 1

[Phil Gillespie]

Appreciate as always all advice as offered. Will get the piston out and have a better look. Then it may be a new set.
Initially thinking of trying for a replacement piston, will probably remove another onne for a correct weight measurement etc and see how it goes. Perhaps even have the piston checked further.
Phil NZ

[Phil Gillespie]

Yes Seth you are correct they are Egge pistons which I purchased from Chassis Engineering as i had a bit of trouble to get these 80 thou over pistons.
Maybe will contact Egge and see what they think?
Phil NZ

[JSeery]

Originally Posted by Seth Swoboda

His pistons look like mine. Mine are Egge. I would assume Egge has a good quality piston.

They do not look the same to me (maybe similar), but I'm sure not a piston ID expert. The OP pistons appear to have an additional machined area around the outer edge of the piston. And the failed piston seems very thin in the failed area. Anyway, I'm not attempting to tell anyone what to do or determine a piston failure based on photos, just saying I would replace all of them while I was at it.

Updated, they are Egge pistons! Maybe just that piston was weak in the failed area? I've never used Egge pistons, but I know a lot of people do.

[Seth Swoboda]

Originally Posted by JSeery

They do not look the same to me (maybe similar), but I'm sure not a piston ID expert. The OP pistons appear to have an additional machined area around the outer edge of the piston. And the failed piston seems very thin in the failed area. Anyway, I'm not attempting to tell anyone what to do or determine a piston failure based on photos, just saying I would replace all of them while I was at it.

Updated, they are Egge pistons! Maybe just that piston was weak in the failed area? I've never used Egge pistons, but I know a lot of people do.

I agree I would replace them all and have them balanced if it were mine. Pistons ain't cheap.

[19Fordy]

Wonder what quality aluminum Egge uses?

Here's the answer and how they are made.
https://www.youtube.com/watch?v=owgcK0TswBM

[Seth Swoboda]

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I'd say he had an engine condition that caused the hole other than a bad piston. Anything is possible though. I do believe he said the spark plug electrode was too long. I wonder what plug he was using? He also has aftermarket aluminum heads.

[flatheadmurre]

If they are Egge gettting 2 replacements isn´t a problem just call them.
Get a good one out and have it weighed then order 2 spares.
If it was me i would take a look at the rest first to make sure they are ok

[flatford8]

The length of the plug reach has been mentioned a few times. If that was so,wouldn’t that BREAK a hole in the piston? To me, it looks like the hole in his has been MELTED. If I’m missing something that everyone sees as obvious, I’ll take getting yelled at by anybody who wants to......Mark

[Cecil/WV]

As already stated, if there is no definite cause for this piston failure, I would replace the whole set. Another piston may give up as soon as you start it up the next time.

[Ggmac]

I'm wondering if part of the plug dropped in , a piece of porcelain ? I guess it'd be in the pan when removed .

[40 Deluxe]

Originally Posted by flatford8

The length of the plug reach has been mentioned a few times. If that was so,wouldn’t that BREAK a hole in the piston? To me, it looks like the hole in his has been MELTED. If I’m missing something that everyone sees as obvious, I’ll take getting yelled at by anybody who wants to......Mark

You are absolutely right Mark! Any time a foreign object or broken plug piece gets in the cylinder it beats the snot out of the combustion chamber and piston top before it exits! As you say, this hole was melted.
If the piston top was too thin from the get-go, it would have shown up when it was weighed at Egge (or the balance shop). It would have been noticeably lighter than the rest of the set and would stick out like a sore thumb!

[JSeery]

Originally Posted by flatford8

The length of the plug reach has been mentioned a few times. If that was so,wouldn’t that BREAK a hole in the piston? Mark

Depends on what you are referring to. The plugs are over the valves, not the pistons. A broken piece of a plug could cause damage, but there is no indication of a foreign object hitting the piston or the head.

[flatheadmurre]

Hard to tell from the pictures if the cause for the hole is detonation...
Usually you hear something if it´s bad enough to melt pistons.

[Seth Swoboda]

I'd be interesting to see the rest of the piston once it is removed.

[Ol' Ron]

I have bored several of these to 3 5/16, with no problem. I think they have the same casting as the standard 59 block.

[Phil Gillespie]

Appreciate as always all assistance given.
The heads when fitted were fitted with the longer reach plugs as recommended by Edelbrock. The two plugs which were sitting too far into the combustion space were closed up only to around 2 thou by the interference of the valves. Nothing was broken off these plugs and nil sign of anything loose hammering in head area.
If the gap is closed up to this extent combustion would not be so good?
This was corrected with the extra seal washer and plugs have maintainned their set gap of 26 thou since fitting.
Once I get this piston out I will go from there.After a good check out. May take it to have it checked out.
Thinking at this stage for 2 spare pistons and rings. As suggested by Mart,
Fit existing rings to new piston and refit after checking both valves.


The removal of sump with engine still in place I understand may require front of engine to be slightly lifted and crank turned to ensure pistons 1 & 5 are towards to top of cylinder?
At least here in NZ weather is still warm now tail end of summer.
Phil NZ

[Pete F]

Is that piston as thin as it looks in the picture.
Can you take a closer picture because maybe the casting was off and the top of the piston was thin so it melted.
I would change them all .


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[Marv]

Originally Posted by JSeery

If it was me, I would be looking for a set of 8 new pistons.

I second that, and a different brand.

[Kurt in NJ]

Using a washer changes the heat range of the plugs, overheated plugs can cause such problems as holes burned in pistons

[Phil Gillespie]

Today got the No4 piston out along with No3for comparrison and weight check.
The line on top at hole is another area cracked ready to let go. The underside is almost suggesting it lrt go from here?
The thickness in the failed area is 7 to 8 mm.
Intact piston weight 400 grams. Damaged is 395 grams. The damaged area as it sits in the bore is on the side where spark plug is fitted. But nil sign of any contact. again the bore is in good order and unmarked as is cylinder head.


Phil NZ