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()*#$(*$
93 Legend L Coupe.
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Discussion Starter · #1 ·
Reading this thread got me thinking. (OH NO!) I have a dremel, sanding rolls, and some time. Why not smooth out the top of my P29 pistons?

BNIB P29s. Yum!


Stock top piston:


Rough going over to get the casting marks off:


The final(ish) product:


I may go over this one again and attempt to clean up some of my hamfisted first attempt. Overall, it's alot smoother and I tried to avoid really sensitive areas like the side of the piston. I don't need that kind of headache. It's not the prettiest mod in the world, but every little bit helps. And, once I put the pistons in the engine, no one will have to see them! heh

Images hosted courtesy of the ZCR, for all your DOH! Cam needs.
 

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Hmm....seems like an ok idea...i'm not sure if i'd trust myself messing with vital parts like that though
 

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I have to agree with CrazyConscious. It seems like a cheap modification but the gain you will get out of it will probably be offset by the fact that your combustion chamber volumes are now unequal.

Some things you hear on the Internet are good ideas and others are just half-baked.
 

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()*#$(*$
93 Legend L Coupe.
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Discussion Starter · #5 ·
Slightly, but it's not that big a deal. I'll be somewhere over 12:1 compression with the final build anyway, so loosing some compression and gaining some detonation resistance is not a bad idea.
 

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Slightly, but it's not that big a deal. I'll be somewhere over 12:1 compression with the final build anyway, so loosing some compression and gaining some detonation resistance is not a bad idea.
did you consider that there might be a reason the top of the piston had a pitted surfave and wasnt completely smooth?
 

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By doing that, some say that takes away from a potential hot spot that could occur w/ the badging.. Still havnt really hear true evidence..
 

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()*#$(*$
93 Legend L Coupe.
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Discussion Starter · #8 ·
Ezeedee-
The reason for the pitted surface is to reduce production costs. It's not neccessary in most stock applications, as the compression ratios will usually not be high enough to warrant such measures are controling detonation. And, as you can see, it's not smooth. I didn't polish the tops, nor would I want to, because if it were too smooth, then the floor of the combustion chamber would not form carbon crystals as easily. If you look at most ceramic coatings on pistons, you will find that they are not completely smooth, either. This is an attempt (albeit a not so great looking one) to replicate that texture to promote better combustion. This is a proven method of detonation control, and since I am new to tuning, I want to give myself as much of a chance to not grenade the engine when it's together.
 

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Ezeedee-
The reason for the pitted surface is to reduce production costs. It's not neccessary in most stock applications, as the compression ratios will usually not be high enough to warrant such measures are controling detonation. And, as you can see, it's not smooth. I didn't polish the tops, nor would I want to, because if it were too smooth, then the floor of the combustion chamber would not form carbon crystals as easily. If you look at most ceramic coatings on pistons, you will find that they are not completely smooth, either. This is an attempt (albeit a not so great looking one) to replicate that texture to promote better combustion. This is a proven method of detonation control, and since I am new to tuning, I want to give myself as much of a chance to not grenade the engine when it's together.
hmm, makes sense i guess. good luck with it!
 

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()*#$(*$
93 Legend L Coupe.
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Discussion Starter · #14 ·
*shrugs* Why not? I've found that I've screwed up a lot less than I thought I would on more critical parts than the tops of the pistons. If I screw them up too badly, I'll get another set and be thankfull my lesson learned only cost me that little. One of the next things I am going to do is mod the oil pump. That is more critical, but I know that I will pull it off fine because I take the time to research what has to be done, and then I just do it that way. If I screw up, well, I learn and move on. That's the only real way to make progress.
 

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I dont trust myself doing anything, Im a fuck up, looks good if you know what you are doing, but for me that is a bad idea.
 

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I would rather keep the tops a little rough. You kinda want the carbons to stick to the tops. It will actually protect the pistons from detonation. Also adding a slight bit more compression. But smoothing out the tops is never a real good idea if using pump gas
 

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Pretty good idea. I'm not sure how effective that'd be, although I guess it'd be cool to try.
 

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The Great Weldini
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it's true i've readed on other forums that if you polish then pistons head it would elimates hot spot but no one post any real proof.
 

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no offense to anyone on here but if you all say you suck and dont trust yourself then 99% of the time that is probably why you fuck stuff up. im a machinist/welder in the military and if i thought that all the time with the stuff i do i dont know what would happen. you guys just gotta try it and mess up and learn. its just the way things go and atleast like beave said hes doing it on something not so crazy expensive atleast. ;) cant wait for the outcome beave :TU:
 
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