Probe Industries Forged Pistons - INSTALLATION DETAILS

D

Doward

Banned
Jan 11, 2006
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Alachua, FL
Here are all the details for your new Probe Industries Forged Pistons!

The following applies to ALL sets of pistons:

THE PISTON RINGS WILL REQUIRE A VERY SPECIFIC FINISH IN THE BORES TO SEAT PROPERLY.

Standard size pistons are in actuality, 0.003" oversize from stock. This is to allow your machinist room to properly hone the block, to get your piston to wall clearances proper.

The .020" and .040" are already oversize, so should present no problem for those of you (like myself) planning on boring the block anyway.

Tell your machinist you are running a chrome steel top ring, so you want a 220-280-400 stepped plateau finish, with a 30 degree crosshatch.

If you are not comfortable with running a chrome steel top ring, then you are free to use any other ring you wish. Remember that the top ring is 1.2mm thick, in whatever diameter you ordered your piston in. For what it's worth, I will be happily running a chrome top ring.

For those planning to run 450-500rwhp and under:

This would be for you guys planning on running an upgraded CT26, or even a larger bolt on, but staying under 500rwhp -

I'd recommend a .0032" piston to wall clearance. If you KNOW you'll be at 500rwhp, I might even say a .0035" clearance.

I'd also recommend a .016"-.018" top ring gap, and .018"-.020" 2nd ring gap, followed with a .013" oil ring gap.

For those planning to run 500+ rwhp:

This would be the group I belong to (and I know some of you others are planning on being here!)

I'm going to run a .0035-.004" piston-wall clearance. I'm going to be running a .020" top ring gap, with a .022" 2nd ring, with a .015" oil ring gap. (I'll be running a PTE67 @ 20-24psi boost, with a 100 shot on top, just to give you an idea of the pressures I intend to deal with)

These are 2618 alloy pistons, so there should be some expansion, but not a whole lot from them.

Also, if you are concerned about the thickness (or lack thereof) around the valve pockets, you can safely take that wall out, with no problems. I'll be removing mine, I know ;)

Any questions, feel free to ask!
 
screaminglemon

screaminglemon

))((
Apr 1, 2005
254
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WA
how would the clearance recomendations change if we are getting these fully coated? ceramic top, moly skirts, and thermal dispersant bottom.

someone, i think ian, was saying the clearances should be up to a thou tighter with coated pistons but these already have a very tight clearance and i would expect them to sieze if i went tighter than .0032".
 
D

Doward

Banned
Jan 11, 2006
4,245
0
36
Alachua, FL
screaminglemon said:
how would the clearance recomendations change if we are getting these fully coated? ceramic top, moly skirts, and thermal dispersant bottom.

someone, i think ian, was saying the clearances should be up to a thou tighter with coated pistons but these already have a very tight clearance and i would expect them to sieze if i went tighter than .0032".
Click to expand...

Even coated, I wouldn't go much below .003"
 
ilikebigbutts

ilikebigbutts

workin' my dream
Jun 10, 2007
347
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35
Pittsburgh
in the spec sheet they give you, it says that for a bore 3.000"-3.624" run a piston to wall min. .004" max.006".i have a very hard time fitting .0065" so i would say i'm at the limit of .006"...now i understand that i will most likely have piston slap at cold starts but am i risking something?i mean they do tell you you are allowed .006".
 
D

Doward

Banned
Jan 11, 2006
4,245
0
36
Alachua, FL
You can, but you'll have piston slap until you are completely warmed up. And for a 400 or less hp build, it will be a serious waste.

Why did you bore so far?

Just curious...
 
ilikebigbutts

ilikebigbutts

workin' my dream
Jun 10, 2007
347
0
0
35
Pittsburgh
i bought the pistons .040" over without knowing the block is already bored out .040"...

BUT!

thanks for your input because i am not planning on over 400whp so i will reuse my stockers that have .0025" wich gives me room for a lil honing/bead blasting the pistons....
 
ilikebigbutts

ilikebigbutts

workin' my dream
Jun 10, 2007
347
0
0
35
Pittsburgh
Doward;902325 said:
Get another block dude! They are easy to find :)
Click to expand...

Easy for you to say!!!

ive spoken with 7 different people and we've gotten down to me almost sending payment and they never get back to me...

i'll stick with a stock rebuild for now...im not looking for over 400whp so i should be fine...
 
90T04

90T04

New Member
Mar 30, 2005
279
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41
Tucson, AZ
www.azsupras.com
Okay, I provided my piston to wall clearance specs to my machinist and he is asking where on the piston they want that measurement taken. I remember reading that somewhere about the probe pistons but I cant find it. He told me that the pistons are tapered and that it will make a difference where they measure for the clearance.
 
ilikebigbutts

ilikebigbutts

workin' my dream
Jun 10, 2007
347
0
0
35
Pittsburgh
90T04;960437 said:
Sounds right, you sound unsure though...:icon_razz
Click to expand...

that's what my teacher told us but we havent had engine class yet.it only makes sense the skirt is the biggest part of the piston.really sounds like your machinist aint the brightest.
 
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