Probe piston issue...please, only smarterer people

[gaboonviper85]

Ok so I picked up a set of probes today...On the intake side of a few pistons where the valve clearance is cut...the clearance is so close to the edge of the that it's damn near knife edged...also on two of the pistons that clearance actually goes out beyond the outside edge.....meaning that if you put the piston face down on a flat surface, the intake side looks like an entrence to a cave moreless..

Sorry for the retarded post but I'm on my iPhone cause my net is down at home...

I'm worried that these could melt on that edge or effect the squish....

What would you do??? As a machinist I'm not the most pleased with the machining of these pistons but I've never built a motor like this so have no idea if this is an issue.

 

[Zumtizzle]

I'm removing the intake side due to some damage.

I'm not really worried as the 2JZ-GE has pistons like this. (with "domes" on all four corners.)


Well i'm paying my machinist to use a Rotary tool and try to match all of them, and then i get to send all six out for a recoat. $$

 

[gaboonviper85]

Yes that! I'm not likeing the looks of it...and I really don't like the idea of
Messing with the squish area...but either I'm gonna call probe and have them send me different pistons or I'll mill that area down a bit at work and make them all uniform with nice radius's

 

[90T04]

Thats how all of the probes are made. I remember reading that they did not have the exact size cutter for the valve reliefs so they went with the next size up...
The edges are quite thin at the tips. But I think the rest of the piston should act as a heat sink and pull heat away from those areas so that they dont become glowing red detonation starters.

I took those edges down about a 1/16th of an inch or so, and smoothed them out.

http://www.supramania.com/forums/showpost.php?p=775565&postcount=444

 

[IJ.]

I'd just blend them with a cartridge roll in a dremel it's nothing to stress over guys.

 

[gaboonviper85]

I'd just blend them with a cartridge roll in a dremel it's nothing to stress over guys.

That's what I want to hear...thanks!

Just wanted to make sure it wouldn't turn the piston into a giant glowplug!

I'll take a diegrinder pen to them (one I use for precision deburring).

 

[IJ.]

If you left em sharp it'd cause more problems

 

[Doward]

ANY set of pistons you buy, take a piece of emery cloth and 'knock down' all of the sharp edges.

Nothing to worry about

 

[Mr. Y]

I'll be installing my set of probes very soon too... My English is not good enough so I can't completely understand what guys (IJ and Doward) do you mean.
Should I grind sharp edge using dremel? Or just install them like they are?
If it's better to grind off, couldn't you make a little picture how much should I remove please? (may be some mspaint)..
Looking forward to your reputable advices. Thanks!

 

[IJ.]

You just want to remove the sharp edges on the pockets where it's marked on the pic up there ^

A 1mm radius is fine no need to go nuts, I do this for all the machined edges on the crowns before sending them to be coated, ditto in the Combustion Chambers.

 

[Zumtizzle]

but either I'm gonna call probe

you might as well bang your head up against a wall.



sorry i forgot to mention you Ian.

 

[boostaddict]

i dont know much about the pistons they make for our cars but probe being a big name i doubt theyd sell them if they were going to harm anything if you know what i mean. i see where you guys are coming from though but id run em and see what happens lol good luck to you

 

[Rennat]

i'll let you know what they look like after a 1500miles... im pulling my head, so i'll take pics to show what that little piece looks like.

i was worried when i got them, but didnt see that big of an issue because probe wouldnt make it that way if it was going to just fail.

 

[IJ.]

Blind faith..... :nono:

 

[Doward]

Will they fail in a stock like application? Probably not. Should you knock down the sharp edges of any piston you use, when shooting for the moon? YES.

Little details like this are the difference between a monster street machine, and broken dreams.

 

[Mr. Y]

Thanks for input, guys.

One more question: what bore diameter do you recomend for +1mm uncoated probes? Target WHP is in 550-600 range (67mm+WI, maybe some NOS on top)...

I remember Doward's instructions but there mentioned "piston-wall clearance" and I don't understand it completely... Does it mean difference between bore and piston diameter or it means distance between piston and wall on each side? (difference in diameters should be doubled piston-wall clearance)

 

[gaboonviper85]

This motor is being built with the idea of maxing a 57 trim ct26...it's not going to be a nitro monster...just hopeing for 400hp give or take.

 

[1986.5supra_kid]

kinda crappy of me but i have used a soft wire wheel for polishing on pistions to remove sharp points. so far no problems.

 

[jetjock]

You must be one of those smarterer people he was talking about...

 

[1986.5supra_kid]

Me? i wouldnt say im smart....