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NOS Nüral piston set review
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raygreenwood
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PostPosted: Sun Sep 22, 2019 9:37 pm    Post subject: NOS Nüral piston set review Reply with quote

Nüral piston set review:

So last week I bought a set of NOS, domed, 1.7L pistons from Heimlich at www.vwnos.com thank you by the way…superb parts and service!

I am always on the lookout for sets of domed 1.7L pistons with or without cylinders. A lot of people in other forums would say…why?

Well…for those of us in 411/412 and 914’s….we tend to restore our cars to factory style/level when we can….partly because they were nice enough as is….and partly because there are not a whole lot of resources to super customize type 4 cars…unless you fabricate everything.

And…that being said….the 1.7L was pretty much good enough for the car in its basic D-jet form with 80hp and dead on reliability to 150k miles. If you are crafty and can tune…you can do a bit better than 80 hp….and still keep it basically stock-ish. With that in mind its worth It’s worth keeping a 1.7L running if you can. The same thing can be said for a 1.8L…especially if you tweak it just a little bit to get around its low factory compression.

I’m doing this review because Heimlich has a few more sets to sell and I think people who look for 1.7L domes should be on the lookout for this brand and these pistons as well….because they look pretty damn good….as good or better than any of the Mahle and Cima pistons I have seen through the 90’s until they became unobtanium….and just short of as good…but may be just as good…as the KS pistons I have.

In over 40 years of working on VW’s and mostly type 4…I had never heard of the brand “Nüral”. However when I saw these months ago on heimlich’s classified ad….I started hunting around the internet for information about them.

The BMW, Mercedes, motorcycle guys and a few other groups have had nothing but EXCELLENT things to say about the quality of these pistons as replacements. Nüral is owned by Federal Mogul. They bought them in about 1998.
https://www.fmmotorparts.eu/brands/nural.html

https://www.enginepartsuk.net/nural-pistons

So….these pistons as they come out of the box…are very well packaged. They have rust prevention paper well wrapped on piston and wrist pin and have great packing. The paper was actually neatly and perfectly applied…it just looks poorly wrapped in these pictures because I unpacked them already before photographs.


From the box legend:

For VW 411 E (E for Einspritzung…fuel injection). This is the same piston for 411 through early 412 (1973) with D-jet and 80 hp. It notes in the lower right corner the piston diameter of 89.96mm. In the left lower its 24mm wrist pins.
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That’s heimlich’s logo on the left

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Now….you will see that these pistons have a strange appearance….a dusty…corroded look…and a sharp acidic smell.
Do NOT be alarmed. It’s normal and correct.


Look closely at the pin bores in these pictures. Notice how shiny they are….no corrosion residue?

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These pistons have the steel stiffeners in them. The last set of late 90’s Mahle/Cimas I got did not have them.

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Again....notice how shiny the pin bores are…more on this in a minute…..

The white residue everywhere on the pistons….and the reason there is none in the pin bores….is because these pistons were “ALODINE” coated…FIRST…and then sent to wrist pin boring/honing…so there was no Alodine on the pin bores. The dust is spent/oxidized Alodine

Alodine is a chromate conversion coating that is used on aluminum and especially magnesium alloys. It is especially used on brake pistons, engine pistons and on some carburetor parts.

FAG brake master cylinder pistons from 30-40 years ago used to have this strange slightly gold to iodine brownish coating everywhere but on the sealing faces of the flap valves and the piston heads. This is Alodine coating.

Alodine is also what was used to coat the cooling manifolds on the type 4 engine that kept them clean for so long. You see this same powdery residue after about 20 years.

Its purpose….is to be a sacrificial anode just like zinc plating…except you cannot readily precision zinc plate magnesium and aluminum (except for zinc nickel in some cases). Its purpose is also to be an oxygen sealer of the surface.

Over a LONG period of time….the Alodine keeps oxygen sealed away from the aluminum or magnesium below it. As long as it’s kept fairly dry, Alodine will not start oxidizing itself. Once it starts….it’s doing its job. The Alodine…oxidizes into a powder so that the precision surface underneath does not oxidize.

That being said….these pistons are now at the limit of their long term shelf life. Most of the Alodine has oxidized into a powder (which is possibly toxic knowing its age).

There was “0” rust and “0” corrosion on the pistons themselves…but you should clean the dust off of these and then wash them in hot water, blow them dry and then oil with WD-40 to drive away any moisture…then pack them back into their rust paper….or use them.

BUT…do not buy these and let them sit for years again without cleaning and protecting them or you may be sorry when you get around to needing them.

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As noted the wrist pins are 24mm (24.003mm actually)

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The piston markings and arrows are normal…diameter and arrow and makers mark. The shiny edge is a burnish mark from the cardboard. Thought it was a dent at first but thankfully no.

The Extent of the Alodine residue:

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The darker brown spots are undisturbed Alodine. The white/silvery island areas are partially oxidized Alodine.

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Cleaning the pistons:

I could have probably used diluted Phosphoric acid faster….but I wanted to be lazy and low risk so a toothbrush and cleaning vinegar ($1.97 a gallon from Wal-Mart) which is 5% stronger solution than regular vinegar.

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I put a half gallon in a 2 gallon bucket straight. Let the pistons soak with some light brushing. It took two cleanings of about 5 minutes each. Then you put a half box of baking soda in a bucket with hot water to dip them in to neutralize…then wash in hot water….then blow dry…inspect…repeat…blow dry….then WD-40.

REMOVE THE RINGS AND SNAP RINGS FIRST!

These ring pliers are poor. I actually went back to just removing them with my fingers.
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After the first vinegar dip:


Note: you can also switch these out of the vinegar and dip in the baking soda and scrub with the soda and it helps.

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You can see the milky residue in the vinegar….after only one piston!

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Still needs a little work

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After the second dip:
Much cleaner…..

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This piston and two others had all black moly coated rings. The one below had the 2nd and oil ring non-coated.

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With the rings back on after blow dry and oiling with WD-40…notice how much cleaner they are.

Also notice that the oil ring and the second ring on the first piston above…are not black moly coated. This was the only piston with a silver ring set. The other three were black. Its marking on the inside was 10-74. The other three were marked 6-72. I have no idea if that is a date stamp…I doubt it.

Take a look at this:

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1. This is an example of how clean they get. They look just fine.

2. I noticed after cleaning that each had a thin “grind” spot on one side of the inside of the skirt. Thought it was just a molding flash they were getting rid of. Check out the logo they were grinding off in the red ring!

I find this these days too. They probably supplied some pistons to VW and had an order for many spares destined for VW. Once the dealer network sells OEM spares the buyer network has to grind the logo off to sell them. I bought new rear strut mounts (F&S) for my 2012 Golf last year from ECS tuning and they were all in VW boxes…but with the logos ground off.

The rings:

The Nüral website…says they use Goetze rings now (Federal Mogul owns them both). But…back then…these are all ATE.

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Piston weights (with rings and snap rings that came on each installed):

549.4 gm
553.8 gm
546.8 gm
547.3 gm

Pin weights:

161.7 gm
155.1 gm
161.1 gm
154.9 gm

Not bad. I am betting that if I measured the length of the pins a couple are slightly longer. I could probably set these up very close just by juggling rings, clips and pins with a little sanding inside a couple of pin bores.
I think these are nice pistons.
Ray


Last edited by raygreenwood on Mon Sep 23, 2019 10:19 am; edited 2 times in total
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heimlich Premium Member
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PostPosted: Mon Sep 23, 2019 9:02 am    Post subject: Re: NOS Nüral piston set review Reply with quote

Ray,

That is an impressive writeup. Thank you.

Marcel
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Lars S
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PostPosted: Tue Sep 24, 2019 8:56 am    Post subject: Re: NOS Nüral piston set review Reply with quote

Nice find Ray, congrats!

/Lars S
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raygreenwood
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PostPosted: Tue Sep 24, 2019 9:05 am    Post subject: Re: NOS Nüral piston set review Reply with quote

Lars S wrote:
Nice find Ray, congrats!

/Lars S


Thank heimlich as well! he seems to have quite a range of parts!
Ray
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EDS411
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PostPosted: Mon Apr 13, 2020 3:46 pm    Post subject: Re: NOS Nüral piston set review Reply with quote

Ray,
I noticed that my engine originally came with domed pistons and I'm assuming these were original . My engine was recently rebuilt with flat top pistons AA. Diameter was correct but they are flat top. Would there be an issue with these? I guess what I'm asking is would the manufacturer have reduced the piston center height and increased the outer portion of the piston to maintain stock compression. Would there be an issue with this.

Regards,
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PostPosted: Mon Apr 13, 2020 5:07 pm    Post subject: Re: NOS Nüral piston set review Reply with quote

EDS411 wrote:
Ray,
I noticed that my engine originally came with domed pistons and I'm assuming these were original . My engine was recently rebuilt with flat top pistons AA. Diameter was correct but they are flat top. Would there be an issue with these? I guess what I'm asking is would the manufacturer have reduced the piston center height and increased the outer portion of the piston to maintain stock compression. Would there be an issue with this.

Regards,


Yes...there will be an issue.

Has the mfg done anything to correct this. No.

Domed pistons with the resulting higher compression are the primary key to how well the 1.7L with D-jet ran.

Is this correctable...yes.
So your engine originally came with domed pistons and about 8.2:1 compression. It had a deck measurement...edge of cylinder opening to the edge of the piston...not the dome itself...to between .068" and .079". Most are .075" to .079"....and a shim that is about .009" on the cylinder base and a head gasket of about .025" when compressed.

Going to flat tops adds about 3.5cc. From experience with flat tops many years ago...that takes the compression down to about 7.8:1....in some cases as high as 8.0:1...about 7.9:1 average.

But....that is still with the head gasket and base shim added in. If you subtract those....and you should not be using the head gasket anyway....that brings the actual deck area from about .079" to about .040"....perfect.

Typically just pulling these two shims out brings normal compression with domes upward to about 8.35:1 or a max of about 8.4:1. With a little tweaking you can hit 8.1:1 and have a .040" deck.

If you have the heads flycut maybe .010"....you can be right back at stock. Ray
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PostPosted: Tue Apr 14, 2020 4:51 am    Post subject: Re: NOS Nüral piston set review Reply with quote

Here's an example of og. Nurals, got the VW logo, collected several non running T4s back in the late 80s, most were virgins, these are dished, bus models.


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PostPosted: Fri Jun 12, 2020 3:58 pm    Post subject: Re: NOS Nüral piston set review Reply with quote

Ray,

Glad to see you are staying a step ahead of the corona virus so far! I know you do a lot of world travel which seems pretty crazy this year.

In an ideal world, what cylinder would you feel comfortable matching these Nüral pistons to? That may be a stupid question, but I see pistons and cylinders sold together so often that I wonder if some magical machining has been done to match everything up. I have also seen a lot of critique on certain piston manufacturers, but rarely cylinders.

Thanks,
Dan
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PostPosted: Fri Jun 12, 2020 4:04 pm    Post subject: Re: NOS Nüral piston set review Reply with quote

Danno5 wrote:
Ray,

Glad to see you are staying a step ahead of the corona virus so far! I know you do a lot of world travel which seems pretty crazy this year.

In an ideal world, what cylinder would you feel comfortable matching these Nüral pistons to? That may be a stupid question, but I see pistons and cylinders sold together so often that I wonder if some magical machining has been done to match everything up. I have also seen a lot of critique on certain piston manufacturers, but rarely cylinders.

Thanks,
Dan


Really thess are/were....replacement pistons for moderate to low miles engines that needed pistons just for an overhaul.

They are destined fro any cylinder that they will fit in. So .....if you have an engine thats has no other problems other than just be old.....and the cylinders can be lightly honed ro put a lean cross hatch pattern on them.....and still have cortect piston to bore tolerance range....they would be just fine.

So even new AA cylinders these would work well in. They ard just veru good pistons. Ray
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Hawker
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PostPosted: Sat Jun 13, 2020 3:56 am    Post subject: Re: NOS Nüral piston set review Reply with quote

Excellent review Ray!

Thank you for sharing this information.
I have rebuilt two 1.7l W series engines a good few years ago now. It was very enjoyable as the aluminium of these Type 4 engines looks so well machined once you get inside.

Best regards,

Rob
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PostPosted: Fri Dec 25, 2020 11:17 am    Post subject: Re: NOS Nüral piston set review Reply with quote

This write-up was extremely helpful Ray. I don't know if you remember, but I turned you on to these Nural's a few years back and asked your opinion on them. Your latest review was enough to make me a believer. After carefully looking through the different types of pistons on the market, I've decided to go with the Nural's as well. I actually put them on my Christmas list, and was pleased to see that I got a set of them this morning.

My engine is in great shape, however, it's never been rebuilt. Since I've gone through and upgraded everything else on the car, I plan on driving the heck out of it. The plan is to slowly collect the necessary parts for an engine rebuild (as my budget permits) and store them until the time comes.

Here are some pictures of the new arrival:

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I'm presuming that the original jugs I have will work okay with the new Nural pistons and rings if they are in good shape. When it comes time for a rebuild, I'll bring the pistons, rings, and jugs (along with the other engine parts) to my VW machine shop and make sure it's a good match.

My friend in Germany has used these 411E 80 PS pistons on several vehicles and he told me the Nural's are virtually 'bulletproof' and further mentioned that they are extremely smooth at idle and well balanced. Of course, it's an exaggeration, but I get his point.

One final note -- These pistons were around $275 USD and I recently checked the site and now they are up to $550 USD. It's a good indicator that the supply is running low! Excited to get a set of these, but hopefully, I won't need to use them for quite some time. Very Happy
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PostPosted: Fri Dec 25, 2020 3:36 pm    Post subject: Re: NOS Nüral piston set review Reply with quote

I remember that you mentioned them in one of your threads or emails....but at that time I really couldn't find that much information on them.

Most of the information I found about them last year was in the BMW and Mercedes forums. It was all positive so I decided to buy a set. Ray
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PostPosted: Mon Dec 28, 2020 10:35 am    Post subject: Re: NOS Nüral piston set review Reply with quote

I just bought my set two weeks ago and they are great! I was able to get them for $295 before price went up. They are beautiful quality
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PostPosted: Thu Dec 31, 2020 11:24 am    Post subject: Re: NOS Nüral piston set review Reply with quote

Ceckert64 wrote:
I just bought my set two weeks ago and they are great! I was able to get them for $295 before price went up. They are beautiful quality


The one posted is the last set I have.
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