NPR piston opinions

[87GWSupra]

Just looking for opinions on NPR piston set from driftmotion. Car is just going to be a DD so not looking for big HP.
Pitting in my cylinders so have to bore out and get the .20 over size.

 

[IJ.]

Cast replacements, keep em out of detonation and they're fine.

 

[suprahero]

Detonation is da debil!!!!!!!

I've used them on George's 7mgte and they worked fine.

 

[87GWSupra]

Sounds good enough to me. Don't think have to worry about det with a stock ge. Definitely micin out skirts see how close they are. Thanks for the input.

 

[rtrdpenguin]

I use them and they're fine

 

[hvyman]

did you have to heat up the pistons for the pins to stick? or did you just slide them in and run it?

 

[IJ.]

Should be full floating like the originals.

 

[hvyman]

ok cool.

 

[IJ.]

The interference fit is in the rod

 

[hvyman]

Just making sure because when i pulled the pistons all the rods could move freely but the pins would not move in the pistons. And Toyota says you need to heat the pistons to 140*f to push the pins in.

When i was taking apart the engine no.5 wrist pin actually moved knocking out the clip and gouging the cylinder wall.

Used engines....

 

[IJ.]

Usually drop the pistons into Hot water during assembly here

They "should" be damn close to 1:1 on the pins so if you handle the pins too much they warm up and expand enough to be a PITA to fit up.

A bit odd in your case with a used engine having a tight fit in the pistons though, maybe some coking or a lip in the pin bore?

 

[hvyman]

Not sure. Will check maybe later today when I go over to my buddy's house since its his motor.

Edit: What also was weird is the no.5 rod bearings were all gold and rough but the crank was good and did not need to be cut.

 

[rtrdpenguin]

I just pushed my NPR wrist pins in by hand without any heat, no problems.

 

[CyFi6]

Every stock piston i have removed from a factory 7m the pins were hard to push out (impossible by hand without hammering) without being heated a little. NPR replacement and my Probe pistons the pins glide in and out no problem at room temp

 

[hvyman]

Ya. I guess its just with stock then. Tsrm says you have to heat them to 140*f to get the pins in or out.

 

[black89t]

The interference fit is in the rod

buzz!!!

wow. i can't believe i'm correcting IJ....actually on the npr's and the oem pistons the interference fit is in the PISTON. the rod has a bushing in it. that is what the piston pin rotates in. hence why it has a bushing. the npr's pin slide in when new. that is true. but once heat cycled the piston pin becomes like the oem pistons. they have to be heated until the pin can be removed.

 

[IJ.]

buzz!!!

wow. i can't believe i'm correcting IJ....actually on the npr's and the oem pistons the interference fit is in the PISTON. the rod has a bushing in it. that is what the piston pin rotates in. hence why it has a bushing. the npr's pin slide in when new. that is true. but once heat cycled the piston pin becomes like the oem pistons. they have to be heated until the pin can be removed.

Are there clips in the piston?

Stock ISN'T interference as I said it's 1:1.....

I don't mind being corrected if I'm wrong but all 7M pistons I've seen have had floating pins, in use the piston expands more than the pin so it can rotate/float, forged pistons expand more so have a small inbuilt clearence.

 

[black89t]

yeah, there are clips in the pistons. its just i don't see how any of the pins in the pistons i have taken out for a 7m could rotate. as they had to be heated slightly to pop the pin out. i'm guessing during warm-up the processes of the dissimilar metals expanding at different rates might allow them the pin to rotate in the piston for a small amount of time.

 

[hvyman]

Well you heat the pistons to get the pins out. At operating temp, which is higher than 140*f, i could see them moving.