Probe Industries Forged Pistons - INSTALLATION DETAILS

[Mr. Y]

Small hijacking: what is "piston-wall clearance."? Is it difference between piston diameter and bore diameter? Or is it distance between piston and wall on each side?

E.g. piston is 84mm, "piston-wall clearance" is 0.1mm, what bore diameter should be for that? 84.1 or 84.2...

thanks

 

[jdub]

It's distance between piston and wall on each side.

E.g. piston is 84mm, "piston-wall clearance" is 0.1mm, bore diameter should be 84.2mm

 

[Rennat]

are there any other details you could share with us?

i got the honing stuff down, any special treatment for bedding/break in of the rings?
just curious... would like everything to go very smoothly when i put everything together!

 

[Rennat]

This thread needs to be bumped, this is GREAT info for people.

 

[sneakypete]

yea great info... bump

 

[Rennat]

my oil rings didnt need any filing...

but you do have to be careful with a piston ring file, as it takes that stuff off quick!

 

[IJ.]

^ Depends on the Ring material.

Plain cast iron 2nd rings are quite soft most top rings are hard and will take longer, file a small amount then check often to sneak up on the correct gaps.

 

[Doward]

IJ's correct. The top rings in these sets are chrome - they are very hard. If you attack the 2nd rings (which are iron) like the tops, you'll eat them up very quickly!

 

[sneakypete]

i just dropped off my motor today with the instructions doward provided. is there anything else i need to let him know (such as filing the rings). this guy knows what he is doing, but i just want to make sure there are no loose ends
thanks
-pete

 

[90T04]

Sorry to revive this thread, but I was just in the middle of gapping and installing my rings, and I found that my oil control rings are already at .020 to .021. I have the 20 over pistons and had the bores set at .0035 piston clearance. Doward, you recommended going with .015" oil ring gap for 500HP and above. Do you think I will be okay with those rings or should I get a set for 40 over and file them way down??

 

[CyFi6]

Can anyone give me any specific tips?
http://www.supramania.com/forums/showthread.php?t=104197

I just found this thread, I only looked in the internal engine section, didn't think to look here.

 

[CyFi6]

Sorry to bring this back up, but now im confused

"
Quote:
Originally Posted by Mr. Y View Post
It's distance between piston and wall on each side.

E.g. piston is 84mm, "piston-wall clearance" is 0.1mm, bore diameter should be 84.2mm

"
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=78

TSRM says to subtract your piston measurement from the bore measurement to find your oil clearance. Does this mean stock pistons have about .0015" of clearance on each side whereas forged have .0035" on each side, but a total of .007" clearance if you do bore minus piston?
Thanks for the help

 

[gaboonviper85]

Sorry to bring this back up, but now im confused

"
Quote:
Originally Posted by Mr. Y View Post
It's distance between piston and wall on each side.

E.g. piston is 84mm, "piston-wall clearance" is 0.1mm, bore diameter should be 84.2mm

"
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=78

TSRM says to subtract your piston measurement from the bore measurement to find your oil clearance. Does this mean stock pistons have about .0015" of clearance on each side whereas forged have .0035" on each side, but a total of .007" clearance if you do bore minus piston?
Thanks for the help

No I believe that's for ring gap....you'll only want a .004" clearance ruffly depending on what this motor is built for (ex. More power more clearance as more heat=more expansion)

Don't quote me but I believe stock pistons have more that .0015" clearance as that's really damn tight!

You need too reread the tsrm and figure out exactly what it's refering too as pistons don't get an "oil clearance"....

 

[gaboonviper85]

Wait you're correct....WTF...but that clearance isn't for "oil" it's for heat expansion....why would Toyota say that?

Stock piston clearance is .0028" to .0035"....not .007 or .0015.

 

[gaboonviper85]

E.g. piston is 84mm, "piston-wall clearance" is 0.1mm, bore diameter should be 84.2mm

this is where you are confused.....we are dealing with just replacing pistons according too the tsrm....you have it all ass backwards dude lol....you measure the cylinder bore first then select a piston that is small enough too give you a .0028" cylinder wall clearance...

Considering you are getting oversized pistons that are forged then forget Toyota instructions....instead what you have too do now is...measure you're new pistons then hone out the cylinder bores out enough too give you a .004" cylinder wall clearance...I say .004" because forged pistons expand more than the cast pistons which is why piston slap is so common in built motors.

Was I of any help or are you still confused?

Too make this stupid simple...say your new pistons where 3.500" wide...you'll need too hone the cylinders in the block too 3.504"

 

[CyFi6]

this is where you are confused.....we are dealing with just replacing pistons according too the tsrm....you have it all ass backwards dude lol....you measure the cylinder bore first then select a piston that is small enough too give you a .0028" cylinder wall clearance...

Considering you are getting oversized pistons that are forged then forget Toyota instructions....instead what you have too do now is...measure you're new pistons then hone out the cylinder bores out enough too give you a .004" cylinder wall clearance...I say .004" because forged pistons expand more than the cast pistons which is why piston slap is so common in built motors.

Was I of any help or are you still confused?

Too make this stupid simple...say your new pistons where 3.500" wide...you'll need too hone the cylinders in the block too 3.504"

This is where i am confused, because Toyota defines the piston clearance (or oil clearance whatever you want to call is, there is a clearance there and oil needs to go there, so i guess it is an oil clearance) how you did, saying the bore needs to be .00X larger than the piston, and that number is your clearance. But JDUB said something different earlier. He said oil clearance is your clearance on each side of the piston, and because the pistons are round you have to take your .00X and multiply by two, so you get (for forged for example) .008" total difference between cylinder and piston size, but only .004" between the piston and wall on each side.

Basically you and previous posters have already said conflicting things, so im not sure who is right.

 

[gaboonviper85]

Yeah my bad it would be .008....sorry I was falling asleep when I typed that previously.

That gap isn't for oil as the compression rings won't let oil pass anyway...it's for heat expansion.

 

[CyFi6]

Are you SURE? The OEM gives a spec for bore size minus piston size, why would probe or any other piston manufacturer do anything different when it comes to giving a clearance spec.? I cant understand why Probe would give a spec for Bore-Piston size= X, and X/2=.004". Just doesnt make sense to me, i would think Probe would give .008" as the spec because the total difference between bore and piston size is just that. Please someone explain this to me in more detail, why exactly Probe would have me measure piston clearance differently than the OEM. (wrote this assuming .004" was the desired "clearance")

Also, even though the rings scrape oil, you NEED oil between the piston and wall as they are a sliding surface.

 

[gaboonviper85]

Toyota spec is for Toyota parts...forged pistons react diff from Toyota cast....pm ij or something

 

[suprarich]

WHOA WHOA WHOA you guys. Piston clearance is measured in "total clearance" not clearance per side. Your finshed size on the bore needs to be the size of the piston PLUS the clearance. And we measure clearance to 4 decimal places not 3. If you want .004 clearance you ask for .0040 not .004. Big difference between those two numbers.