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Discussion Starter #1 (Edited)
This is sort of a continuation of another older thread
http://www.camaros.net/forums/showthread.php?t=95821
I was supplied Seal pro as ACL Aussie pistons where not avaliable at the time.
and was assured they where good pistons
The fine print on the label in the box says "made in Mexico"
After stripping the engine we found #5 dia fron just below the ring and bottom of the skirt was 24/1000 !!!
This related to the position of the knock with a stethoscope.
All the other pistons also have a similar thu smaller diff in dia.
The knock started shortly after 1st fire while still doing intial cam bedding in.
Such collaspe as far as I can gather is caused by poor alloy or casting as the piston heats up and or the diff in diameters where there before machining and fitting/final hone of the cylinders, the latter was checked before assembly
Im having problems with the supplier in NZ here
Has anyone had problems with these pistons?
 

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Discussion Starter #3
SBC 350 40/1000 over...fully balanced engine...built for economic bottom end street around town general rpm range 1200 to 4000 rpm.
Rebuild included new water pump, oil pump, fan clutch, raditor header removed and cores cleaned.
Cast rams horn manifold.
New cam, valve train, rebuilt heads, new valves, springs.
intial run in on Zn oil, oil/filter change at 50 to 100miles...engine now dismantled at less than 500 miles.
Car was put on dyno for mixture checks, dizzy curve etc within the 1st 20 miles..all checked out spot on.
Plugs all read good..center plugs read spot on burn with cnr plugs slightly rich which is normal on a performer dual plane
There was no sign of the piston box damaged or dropped nor any sign of a piston dropped before build or after dismantle.
The box and paper with part # was lost when the apprenice cleaned up the workshop....cast flat top pistons SBC 350 40/1000 over with moly rings.
 

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Do you mean Speed Pro pistons? I'v enever heard of Seal pro pistons, but that's not to say they don't exist.

I originally bought Speed Pro's for my motor, and my machinist wouldn't use them. He said that size-wise, they were "all over the place". I'm sure in machinist-speak that means a few thousandths or less - but anyway - he didn't like 'em.

Disregard if there actually is a Seal Pro piston.
 

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Sealed Power is a cheaper division of Speed Pro. I've never had any problem w/Sealed Power, but this has been over 25 yrs ago.
 

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Steps,
What is the actual part number of the piston ? Should be on the top if they are Speed Pro's. Is there a size on the top ? Were the pistons measured before installation ? ...... Just thinking out loud :)
 

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Discussion Starter #8
Sry bit of misformation above...what with hassles with supplier and just have too many unrelared things on at the same time...
Pistons are SEAL POWER .040 over
The only numbers can find are in side the piston..
1436 05

2 have 311
1 has 350
1 has 315
4 have 330

P/W clearance is all cool...each cylinder was final honed to each piston individually
 

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First of all, I think we need to see one of the pistons, how about a picture ?

Silvolite, Badger and others make pretty decent pistons. They are equivelent to what most manufacturers use in stock engines. Silvolite also makes the Keith Black pistons, which are fine as long as they are installed pproperly and thier limitations are known.

Steps, your "numbers" dont make any sense to me ? What do you mean by the piston measuring 24/1000 ? Are you telling me that the piston in question had .024" Piston to wall clearance ?

If the piston got hot enough to collapse it, you have some other problems, in my opinion.
 

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Discussion Starter #13
Steps, your "numbers" dont make any sense to me ? What do you mean by the piston measuring 24/1000 ? Are you telling me that the piston in question had .024" Piston to wall clearance ?
No that is how much #5 piston shirt has colapsed!!!
Diam justbelow the bottom ring
Minus
Diam at the bottom of the shirt
= 24/1000" and thu that is the worst, ALL of them are nearly as bad.

1436 is a Silvolite piston number, not Sealed Power.
Now this starts to get even more interesting..Im not doubting you guys..that why Im not wasting my time askingt here asking
So what would Silvolite pistons be doing in a Speed Shop in Sealed power boxes...
If the piston got hot enough to collapse it, you have some other problems, in my opinion.
The engine/piston HAS NOT got hot or over heated!!!!
The knock was there when 1st fired up and run the cam in....
It is a LPG designed Stump puller engine ...they run cold, max temp reached was just under 170*....The engine has now been Completly stripped...there is NOTHING to signify ANY over heating /wear or ANYTHING like that ANY WHERE.
Repeat Raditor had headers removered and physically cleaned out the cores etc...New oil pump and pressures at all times was great...Dyno just after break in to confirm dizzy curves /mixtures etc

I have had this matching number '69r for 27 yrs AND going to keep till I reach my use by date in another 25/30yrs...Hence why EVERYTHING is fully balanced, 2x and 3x checked, plasti gauged...
Other than the knock this car performed exactly as I designed it to do (no a bit better than that)...from designing the billet cam to machining in the dizzy to get the right curves.
Sry for sounding grumpy m8...Im not..put it down to my Kiwi accent lol
Pics...everything has just gone down counrty to my machinest to be re balanced new Aussie ACL pistons, honed etc etc.
Sat here will see if I get time on Mon to drive down on Monday.
What how where angle do you want pics of the piston(s)?

Have had 3 other experts look at them now
2 say "crook pistons, either they where colasped before install, or a bad alloy/casting and collasped as the engine warmed up"
1 says hes "sent several of these back to suppliers because of suspect bad casting before...looks like collasped as the engine warmed up"" At the time I did not mention brand name or anything like that..just let him look at them and comment un biased.

Realy appreciate your support guys
Steps
 

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Steps,
Did you measure all of the pistons ? Most pistons are "barrel" shaped and the area directly below the oil ring groove is not the correct place to measure them. The correct measuring spot is usually at the bottom of the skirt or a little above the bottom. I have seen some older forged pistons that were measured 90 degress to the wrist pin, but never a cast piston. I think there is more to the story and its impossible to tell without having the parts in hand :(
 

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Discussion Starter #15
measuring 90* to the gudgen have to cause thats where the skirt is
From just below the bottom ring is to the top of the skirt is fine
From this piont down the collaspe takes place.
Yea measured all pistons nores etc etc
Yes they all vairy from 15/1000 to 24/1000
Those sort of tollerances one can actually see the bend
 
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