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Discussion Starter #1
How to fix mild pre-detonation on forged pistons.

The subject pistons are Wiseco pn 6595M85
+14 cc dish pistons w/ H.D wrist pins
03-07 Evo VIII

The pistons came into my shop with slight damage around the thin wall of the eyebrow on the outer edge.
They were hung on Eagle rods.
To me it looked like hot spotting and pre-det.



Notice the damage on the outer edge of the piston?



the first step is to remove the piston from the rod.
That is done by removing the C clips from the wrist pin bores.
Be careful not to bend or deform the clips, or you will have to order a new set form the piston manufacture.



Next is to mic the piston to make sure it is within spec.
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Next using a small burr I ground away the damaged aluminum

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After that I used a flapper wheel to smooth any rough spots and to remove the galling

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I also removed the sharp edges (90*) that was from the machining of the piston when it was first made to help eliminate and more hot spots.

Next the pistons were glass beaded clean.
 

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96 Ranger-stock
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Discussion Starter #2
Now to maintain balance, the piston were weight matched within .2 grams


Next I checked the balance on the rods, starting with the small end.



After all the small ends were matched.



I balanced the overall weight of the rod, also keeping the balance with in .2g .



Now it was time to hang the pistons on the rods.

 

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96 Ranger-stock
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Discussion Starter #3
I start by installing one of the clips in each piston.



After that is done, I oil the wrist pin bores in the piston.


Also oiling the small end of the rod.


Then oiling the wrist pin
.

Then sliding the wrist pin through the piston and rod, Making sure the piston faces the proper way on the rod.



The last step is to install the other wrist pin clip and making sure that all clips are seated in their grooves and the rod floats smoothly on the wrist pin.

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Damn. Once again you impress
 

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Well, Whoever installed the pistons Shouldve sanded down the sharp edges. Forged pistons are rarely ready to install right out of the box. :facepalm:
 

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Discussion Starter #11
Well, Whoever installed the pistons Shouldve sanded down the sharp edges. Forged pistons are rarely ready to install right out of the box. :facepalm:
I can understand what you are saying, but how many first time engine assemblers want to take a grinder or sand paper to there brand new $500 set of pistons right out the box?

It is hard enough to get them to check ring gaps let alone have them debur a set of pistons, Most do not even need to for the power level they are making.

The best set i have seen out the box were JE, They were dressed right out of the box, and the weight was almost perfect.

Wiseco out the box are decent and need minimal hand dressing.
 

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Where do you remove weigh from on the pistons? Dead center above the wrist pin?
 

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EG8
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Where do you remove weigh from on the pistons? Dead center above the wrist pin?
Correct me if I'm wrong, but I think I saw someone remove it from the width of the walls at the bottom.
 

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Discussion Starter #15
Different machinists remove it different places, Some drill it under the crown of the piston, some inline of the piston, other on either on either end.

I do not like that, I feel it can lead to thin spots in the crown, and make the piston weak at those spots.

I polish around the wrist pin boss.
 

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Different machinists remove it different places, Some drill it under the crown of the piston, some inline of the piston, other on either on either end.

I do not like that, I feel it can lead to thin spots in the crown, and make the piston weak at those spots.

I polish around the wrist pin boss.
This is 100% correct.

I asked a few local machine shop and the Legend Pat Primmer where he thought i should take the material off of my vitaras pistons to balance them and this is exactly what he had told me to do also..

OP keep up the good work, Lots of good info your posting
 

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Funny thing is i was watching powerblock and when they installed their pistons, they kept the tops nice and shiny. An older version with the old crew deburred them the right way and scothbrited the tops.. but yea, for the noobs, piston tops shouldnt be like a mirror.
 

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FWIW, I have heard it wise to tape off the ringlands when glass blasting, which I think is a good idea.

The reason, is that the ring seal against the piston is as important as the seal against the cylinder and roughing it up may cause blowby and loss of power.

Maybe put a wrap of masking tape around the ringlands when blasting, then a hand sand to clean it up and make it look pretty.

I agree it's a joke some builders are "Hassled" with checking end ring gap. I checked everything 3 times over 3 days 3 different temperatures before I was satisfied.

I have also heard Forged pistons come with the wrist pin bore slightly undersized to be honed to spec.

The more I learn about an engine, the less I want to take it to a shop because I know the 1000 ways they can mess up, like drilling a piston crown to balance it.
 

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Discussion Starter #19
Toaster... this is the first time I have hears of a ring sealing to the piston.

The ID of the ring is still larger the the back of the ring land.

Unless you think it seals against the top or bottom if the ring land, but it can not there either due to piston movement allowing the ring to flex down on an up stroke and up on the down stroke.

Also take into account gas ported pistons, they have small jet ports around the crown of the piston to allow combustion gasses behind the top ring to help force the ring into the cylinder bore.

Now depending on what grade glass bead or blasting media is being used I could see caution being needed as not to knurl the ring lands tight.

I doubt even some of the more aggressive can be ad damaging ans a ring land cleaner.

If there is any knurling effect from the pistons I glass bead, are quickly polished away from the sides of the rings flexing.

Now I will tape off the skirts of coated pistons if the coating is for the most part is there, if not I will glass bead it away to change the texture of the skirt surface, my thought is it will hold a bit more oil on the skirt.
 

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EG8
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I can understand what you are saying, but how many first time engine assemblers want to take a grinder or sand paper to there brand new $500 set of pistons right out the box?

... *snip*
That point alone made me scared/question this video a while back:



I guess my idea back then was they cam fresh out of the factory, they should be 100% perfect!
 
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