ulakovic22

iTrader: (12)

I have a new set of Wiseco pistons (PT102H6) and had every intention on e-mailing Brian to see what his thoughts were, but when I did a search I couldn't find any info readily available so I thought I would post this question to everyone.

On a new set of pistons there are plenty of sharp edges and places for hot spots and I've read and seen several "prepped" pistons where builders have actually media blasted or sanded down the piston tops to help alleviate this. There have been a few tests of this theory and it has shown more power and less detonation as well as other I'm sure. So my question is this, what kind of material or media do you use to do this? Are there any guidelines that someone who has done this before follow? Any things to look out for? I know one thing would be the actual piston CC when removing material and it's effect on CR.

Thanks,
Anthony

mrdragster1970

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We smooth out the edges you're talking about with sand paper rolls. Just try to take off the same amount of material from every piston.

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ulakovic22

iTrader: (12)

Are we talking a multi step process using like 220 to remove material and shape and then something a lot finer to smooth everything out?

WE TODD DID

iTrader: (2)

Scotchbrite pad works good.

FASTFATBOY

iTrader: (23)

I use 80 grit emery cloth and my right thumb

Dont just do the eyebrows, do the straight line across the face also.


Do the edges of your combustion chamber of your head to.


David

briannutter

Hey there, I answered your PM, but I'll post the answer here as well because everybody should do it. All CNC pistons are subject to sharp edges and hand deburring only helps a bit. When we introduced our CNC Diamond Brush operation on our customs and now our 2008 LS parts, some customers actually complained because they went from shiny to dull...the combustion loves the smooth finish though

We use a radiused cutters for some valve pockets and for increased airfllow around the intake valve at tdc. The exhaust should normally be "stood up" with a small radius at the top because air flows OUT of that valve.

Be careful about doing too much work between the valve pockets...radius it if it's pointed, but try not to make it any deeper than what it is...it's one of the highest stress points on the deck of a piston. On our Big Block parts like yours, we lathe turn domes prior to machining the perimeter to lessen the edge at the top.

When a valve pocket comes off the edge of a piston (like a L92) exhaust pocket or Ford Cleveland intake pocket, there is a REALLY sharp edge at the ring land intersection that needs to be rolled back with a cartridge roll. If you don't, it will turn into a glow plug and snap off. In some cases, some piston manufacturers neglect to do a spot mill at the outside of the intake pockets (required on some engines) that leaves a very thin and tall ridge. This will ALSO turn into a glow plug and snap off. If this ridge is anything less than .100 wide, grind it down with a carbide-followed by cartridge roll work-followed by crossbuffs-then a final round of scotchbrite. The ring land will get thinner at this point (sometimes as little as .080" to the ring groove on a .250 top land), but it's better that the glowplug scenario.

As for reduced compression, 2618 alloy is 2.76 grams per cc..that's a lot of polishing necessary to reduce volume much. You can measure a piston before and after to see the difference you made. Hope this helps. Brian Nutter-Wiseco Piston

ulakovic22

iTrader: (12)

Hey Brian, thanks for jumping in with some great info. On a side note you wouldn't happen to have any pictures of the pistons I got from you guys would you? I'm VERY excited that you guys started your low dome line of pistons, it makes things very easy for us BBC guys to run something on the street without a lot of work or the extra expense of ordering custom pistons.

Also would glass beading be acceptable to finish off the piston tops like the one above or would the scotchbrite be the best thing to use?

briannutter

Hey there, here's a pic of the piston in the 4.530 bore size. Notice that the width at the side of the intake pocket (next to the land) is wide enough, so you won't have to relieve it. This particular piston doesn't have a radiused intake pocket because that would remove material next to the top land, but you can lay it back some in the middle of the pocket for additional airflow.

The smaller bores (4.500) on that piston series are at our minimum width for material outside the pocket...when you reach up to the 4.600" size for that piston, it automatically puts another .050" worth of material out there. When guys have problems with lands lifting, often the best way to fix it is going to BIGGER bore instead of making the valve and valve pocket smaller or going to a reduced radial top ring. In particular on this piston, I'd cartridge roll the exhaust pocket into the dome, lay back the intake pocket a bit and radius it into the the dome as well. I'm all for the bead blasting, but the part will have to be very well masked and you'll thoroughly have to clean out the pin oiler as well.