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Sun Jul 15, 2018 9:47 am

Has anyone ever heard of a “bad batch” of NPR pistons and cylinders? All of the older engine builders that I know and have spoken to have stated that they never heard anything about this. According to one source in a shop in CA. when my friend mentioned using them for his build the guy strongly advised against it unless he was able to measure all of the cylinders on the spot. The source told him that there were heating and cooling issues with a batch that resulted in cylinders that were out of round. I have my own theory as to why this source told my friend this but I will keep that to myself. Any insight is appreciated.

Sun Jul 15, 2018 10:26 am

Hoody wrote: Has anyone ever heard of a “bad batch” of NPR pistons and cylinders? All of the older engine builders that I know and have spoken to have stated that they never heard anything about this. According to one source in a shop in CA. when my friend mentioned using them for his build the guy strongly advised against it unless he was able to measure all of the cylinders on the spot. The source told him that there were heating and cooling issues with a batch that resulted in cylinders that were out of round. I have my own theory as to why this source told my friend this but I will keep that to myself. Any insight is appreciated.

NPR?...Nippon Piston Ring?

Unless I am just not looking in the right place....and please show me.....I cannot find any offerings from NPR for aircooled cylinders for VW. They have plenty of listings of pistons, rings, pins and liners for modern water cooled cars.....but as far as I am aware.....and I hope I'm wrong....NPR has not produced aircooled VW piston and liner sets since maybe the early 1990's.

All that I have seen are NOS. And...I have never seen an issue with them. They were decent quality overall....about as good as the Australian built Repco pistons.

Ray

Sun Jul 15, 2018 10:38 am

In lieu of available KS or German Mahle my next choice would be NPR, downhill from there. Like Ray I know of no new offerings from them for air cooled VW's. I have used them and would not hesitate to use a set of old stock NPR over the offerings available today.

Sun Jul 15, 2018 11:57 am

NPR, back in the day were good quality pistons and cylinders. Installed a few hundred sets. If I remember they had a cartoon guy on the box, winking. Its been a long time since I have seen these. That company went under years ago.

Sun Jul 15, 2018 1:39 pm

I think your all newbs. :P
It's very easy for these cylinders to go out of round for any reason, especially if they are thin wall, and some of the sizes were quite thin.
And I think the guy who was complaining about the bad batch, was probably overreacting about how bad it really was, although, a "bad batch" certainly could happen. If it can happen to chevy and ford ect ect,, it could happen in Japan too. We think of iron as being as stable as granite, but it really isn't. There are many tricks used to make it stable and de-stress so that it does stay straight after final machining is done.

NPR usually makes very good stuff. Most Wiesco pistons come with NPR rings.
It stands for NIPPON PISTON RING

Sun Jul 15, 2018 3:53 pm

VW_Jimbo wrote: NPR, back in the day were good quality pistons and cylinders. Its been a long time since I have seen these.
Way back in 1976, I assembled my first 1835cc engine using NPR cylinders and pistons. Yes, Nippon Piston Ring, not National Public Radio....

Sun Jul 15, 2018 3:59 pm

That source is FOS.
NPRs were very common in the mid 70s-early 80s, had lower prices & were of average quality.
I've also used many sets of them w/out any issues, running mostly right outta the box. The few sets that I did prep/blueprint were very close as I recall - overall a big step better than anything from Brazil @ the time.
They were soon squeezed-out by Brazilian competition & became history, but certainly had fewer QC issues than the current chinese imports.

Edit, just looked them up. About 7 miles away.
If anybody recalls the fine ol' days of the SoCal Hot VW scene, they will recognize the 'hood - remember the 1st Auto Haus, or Johnny's Speed & Chrome?
The new NPR is now located 1/2 mi W of where the above iconic landmark sites once were. Both have long since been redeveloped:
NPR of America - 7001 Village Dr #240 Buena Park, CA 90621
Auto Haus - 6315 Beach Blvd. Buena Park, CA 90621 (now a large biz center)
Johnny's - 6411 Beach Blvd. Buena Park, CA 90621 (now a Honda auto dealer).

Sun Jul 15, 2018 5:45 pm

The interesting thing is that everyone keeps saying NPR....folded up or went out of business. They have never gone out of business.

I think they just pulled a lot of low volume parts out of the US market. Or maybe for a time left the US market.
I was just looking at their history. Been in business since 1934....and has been expanding ever since. One of 3 primary piston ring mfgs in Japan.....major production for Chinese and Indonesia mkts.....and signed a global supply agreement with Kolbenschmidt in 2007.

NPR USA I think was cranked up or restarted in about 2011 consolidating the Michigan and Kentucky mfg plants.

Scroll down this page to their history timeline.
https://www.marklines.com/en/top500/s500_203

Ray

Sun Jul 15, 2018 7:08 pm

I have NPR pistons in my 1988 Mazda B2200 truck, installed those in 2011.

Sun Jul 15, 2018 8:37 pm

I too believe the source who told my friend that about the NPR’s was totally FOS and had ulterior motives. A friend of mine who is currently building a type 4 engine for a 914 is using a set of 96’s he’s had in his stash for a long time. His opinion is that they were the best P&C’s ever made for a type 4 motor. Superior to the German KS and Mahles. This friend of mine has been building motors for 40 years. But everyone’s opinion differs. There are no current offerings for type 4 engines. Just NOS. And not easy to find. Thank you all for your replies. My suspicions have been validated.

Sun Jul 15, 2018 8:39 pm

Why don't you just measure the cylinders and find out???

Sun Jul 15, 2018 8:51 pm

My current motor has TW90mm NPR's in it. The motor was assembled in the late 80's and then sat for 20yrs beginning in the mid 90's, they have 5--60K miles on them. When I got it running again, other than having to source a new cylinder due to water/rust in it (and I got lucky and found one locally), I only put new rings in them and they are fantastic.

Sun Jul 15, 2018 8:56 pm

I suggested to my friend who is having an engine built to buy them and have his builder do that. I am on the other side of the country so I can’t help him. If I am not mistaken if he buys them with PayPal and picks them up and by chance they are out of round he can return them and is protected by PayPal’s gaurentee. Even if the seller strictly states no returns. He’s in Cali so I am not familiar with that states policies. But in my eyes a faulty part that is unusable can be returned for a full refund regardless of a store’s policy of no returns. This friend is completely new to the aircooled engine world. He’s afraid of buying them, having them turn out to be bad, and not being able to get his money back. Short of him inspecting them for corrosion and broken fins I seriously doubt there would even be an issue. But the source I mentioned who I think had ulterior motives scared him about it being possible. I would be way more concerned about the current offerings myself. My engine builder friend told me the NPR’s were within a gram difference between the four P&C’s out of the box. Try to find that these days. My friend would not know how to nor possess the proper tool to measure them.

Sun Jul 15, 2018 9:10 pm

IMO they should be honed anyway, get a fresh hone on them before they are run, if they are very old.
Before honing them I would measure them, for free or maybe for 20$
Look AERA directory and find local machine shops

Building any engine, the cylinders should be measured, skirt clearance checked, rods checked for alignment, and all the other things it says to do in the manual. It's always been that way.
Guys skip it......that's their own choice. Even if they are .003 out of round, it's not the end of the world. There are things that can be done, to fix it.

One of the tricks to make iron stable is just WAIT. Set the4 castings sit for a year or two before finishing them. So, if that was the original problem....it's fixed now!!! :lol:

Sun Jul 15, 2018 9:12 pm

From my experience....replacement piston wise.....not so much cylinder wise.....the 1980s NPR pistons and the Repco pistons.....were well made, nearly exact knock offs of the facy2ory stock KS pistons.

Piston wise they both did a damn good job. I still have a set of 90.5mm domed Repco pistons in my stash. Ray

Mon Jul 16, 2018 7:08 am

Hoody wrote: But in my eyes a faulty part that is unusable can be returned for a full refund regardless of a store’s policy of no returns.
Yes, this is called the law of merchantability.
https://consumer.findlaw.com/consumer-transactions/what-is-the-warranty-of-merchantability.html

https://www.google.com/search?source=hp&ei=hKZ...KGDHxV-27g

Mon Jul 16, 2018 8:11 am

After some reading it looks like if the seller says “no returns” or “as is” then the buyer is stuck in Ca. That’s why I thought he would be protected under PayPal’s policy. I still think it’s a mute point. All that I could do was to suggest that these P&C’s were his best choice for his build. Thank you all very much for your replies and experience with these!