NPR piston measurement?

[redhot91gt]

Have all my measurements on my block, and was looking to replace all my pistons. I was wondering what I can expect as far as measurements on the standard sized NPR pistons. If anyone has measured their own or has the factory measurements or something I'd appreciate it.

Thanks
-Stu

 

[hvyman]

well the best way to go about that would be the next size up pistons and bore the cylinders to match the pistons.

a set of pistons still has slight difference is sizes and when the cylinders are bored to match the pistons, they should be numbered with the cylinder they were bored to match.

 

[redhot91gt]

well the best way to go about that would be the next size up pistons and bore the cylinders to match the pistons.

a set of pistons still has slight difference is sizes and when the cylinders are bored to match the pistons, they should be numbered with the cylinder they were bored to match.

I understand that, but I am trying to get this done with just honing a little bit, Just need to double check on what about the measurements are on those to see if my oil clearances will be ok.

 

[WhtMa71]

Stock sized NPR pistons should be, well...stock sized. Measure your bore, find stock piston size, compare to stock piston/wall clearance according to TSRM. If it's over, might want to go +.020 on the pistons and get it bored/honed accordingly. Make sure to tell your machinist your target piston to wall clearance.

 

[CyFi6]

There are hardly any STOCK SIZE or STD SIZE parts in a 7m. Ever heard of select fit? Pistons, rods, crank, bearings, cylinder bore, everything is select fit and comes in about 5 different sizes of each. There is no one STD size so it seems he is trying to figure out if he can use the "std size" npr's with his select fit stock Toyota bores and still get an appropriate piston to wall clearance.

 

[WhtMa71]

OK then sounds like he's SOL without a set of pistons in his hands...
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=78

 

[CyFi6]

Is there no spec sheet for these pistons anywhere?

 

[redhot91gt]

OK then sounds like he's SOL without a set of pistons in his hands...
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=78

I have a set of stock pistons, but they are number 2's. Just trying to find out if anyone has ever measured their NPR's. It looks like I am going to have to buy a set and check myself. If they wont do then I will just re-sell them. I'll post measurements in here for future reference.

 

[WhtMa71]

I have a set of stock pistons, but they are number 2's. Just trying to find out if anyone has ever measured their NPR's. It looks like I am going to have to buy a set and check myself. If they wont do then I will just re-sell them. I'll post measurements in here for future reference.

Try and get one of the sellers to measure a set for you..granted they know what they're doing..

Actually, I'm sure Aaron at Driftmotion could help you out since they sell them.

 

[hvyman]

why dont you just use the stock pistons? same thing as npr basically.

 

[redhot91gt]

why dont you just use the stock pistons? same thing as npr basically.

the ones I have? well my number one cylinder had low compression, the pistons looked like they were getting hot. (bad tuning + too much boost) and #1 has a very small crack on the 2nd compression ringland which is probably why I only have 75psi in that cylinder. No there are not any scrapes/gouges in the cylinder. I suppose I could try to order just another piston and a set of rings, but I am worried about the used pistons, because they may have gotten hot aswell. Buying all new toyota pistons is a little expensive for me. If I have to go that route I might just go ahead and go forged and bore it out.

 

[IJ.]

New pistons in old holes is a bad idea as they're NOT going to be straight and round.

Even a light hone to break the cylinder glazing is going to make the piston to bore clearence way too big for cast pistons and it will slap like a bitch.

 

[hvyman]

npr is not forged. there stock replacement pistons. probe's, je, weisco, cp etc.. are forged.

 

[redhot91gt]

npr is not forged. there stock replacement pistons. probe's, je, weisco, cp etc.. are forged.

Please... I never said NPR's were forged. I dont know where you got this from what I was saying.

 

[redhot91gt]

New pistons in old holes is a bad idea as they're NOT going to be straight and round.

Even a light hone to break the cylinder glazing is going to make the piston to bore clearence way too big for cast pistons and it will slap like a bitch.

So I guess its time to get some oversized pistons and bore it out then.

 

[IJ.]

I would if I had further plans for an engine and wanted to make it reliable.

 

[redhot91gt]

I would if I had further plans for an engine and wanted to make it reliable.

True, I definately wouldnt want to build a grenade..

 

[Supra28]

I just ordered standard size NPR pistons last night too, bad idea since I plan get the cylinders honed. Spoke to Aaron from DM and was able to change the order to the .20 over's. Whew!

 

[hvyman]

the ones I have? well my number one cylinder had low compression, the pistons looked like they were getting hot. (bad tuning + too much boost) and #1 has a very small crack on the 2nd compression ringland which is probably why I only have 75psi in that cylinder. No there are not any scrapes/gouges in the cylinder. I suppose I could try to order just another piston and a set of rings, but I am worried about the used pistons, because they may have gotten hot aswell. Buying all new toyota pistons is a little expensive for me. If I have to go that route I might just go ahead and go forged and bore it out.

Please... I never said NPR's were forged. I dont know where you got this from what I was saying.

i must have read it wrong. my apologize.