I'm rebuilding this engine from the ground up and have most of the pieces I need already. The block was trashed. So, I'm waiting for a block from a "near by" (out here that's about an hour's drive) salvage yard, should be picking it up early next week. Since I don't yet know the condition of the cylinder bores I'm holding off on ordering pistons. But after doing a little searching on ebay I wanted to get some opinions on piston brands (I don't really want to spend $350-$450 for pistons for what's going to amount to a basically stock setup either).

It looks like the choices are NPR, Nakamoto, and TopLine.

Anyone have any experience with any of these?

And if I did decide to spring for Wiseco or JE pistons, do they work with stock rods? I've already got a set of reconditioned rods on order.

I've never had any experience with topline pistons. But most of there products are pretty good.

partsdinosaur.com The answer to your stock engine parts needs. I believe he sells Topline. He is my main source for stock engine parts. For the record, Topline has a relatively good reputation. I have used their pistons a couple of times in the DSM motors with no problems. One of my machine shop buddies uses them in some of the engines he rebuilds. No problems.

Originally posted by Zardoz
I'm rebuilding this engine from the ground up and have most of the pieces I need already. The block was trashed. So, I'm waiting for a block from a "near by" (out here that's about an hour's drive) salvage yard, should be picking it up early next week. Since I don't yet know the condition of the cylinder bores I'm holding off on ordering pistons. But after doing a little searching on ebay I wanted to get some opinions on piston brands (I don't really want to spend $350-$450 for pistons for what's going to amount to a basically stock setup either). It looks like the choices are NPR, Nakamoto, and TopLine. Anyone have any experience with any of these? And if I did decide to spring for Wiseco or JE pistons, do they work with stock rods? I've already got a set of reconditioned rods on order.

IIRC you cannot use stock rods with JE's or Wiseco's. Not only that, but if you are going to dump the cash on a nice set of forged pistons, why would you connect them to crappy powdered metal rods anyway? There is no sense in having a piston that will handle 400+HP and a rod that will break shortly after half that number. Just my .02

^^^^x2

Originally posted by Fallen4ng31
...why would you connect them to crappy powdered metal rods anyway?

Your point about spending that much money for pistons and leaving such a weak link in the formula is well taken.

But, the way I read your post, I think you might have a slight misconception of powdered metal technology. The stock rods might be "crappy" (especially for the 400hp application you describe). But, I would think it would be a product of their design not the fact that they are "powdered metal." With my background in V8's, when I hear "PM rods" I'm thinking LT1s LT4s and other high performance GMs.

Even in the after market:

SuperChevy.com
Howards Racing Components' powder-metal Forged Rods Come Darn Close To Unbreakable

Powdered metal rods are even making their way into heavy duty diesel applications. Talk about stress on a connecting rod!

So, I'd say it is the design not the material. But your point is well taken. It doesn't make sense to spend that kind of money on pistons when the rod will be the weak link in the chain.

Just my $.02

Now, this all brings me to another question. I'd rather have hyper-eutectic pistons rather than just standard cast. And I found that Federal Mogul (Speed Pro) makes a hyper-eutectic for the 95-99 DOHC Neon, p# - fmh853cp. Now, since the only difference that I've found researching this engine is that the intake and exhaust are reversed on the head, will these pistons work for our 420a's?

Yes they will.

And he is right, its the design for THIS application that makes these rods so weak.

Originally posted by Zardoz
I'd rather have hyper-eutectic pistons rather than just standard cast.

Stock pistons are hypereutectic.

Originally posted by DarkOne
Stock pistons are hypereutectic.

The stock OEM pistons likely are these days (not quite so in the mid to late 90's). But that doesn't necessarily mean aftermarket replacement pistons are.

The technology to achieve an aluminum/silicon alloy higher than approximately 12% Si (~ 88% Al/12% Si is a "eutectic mixture") for cast pistons was developed in England and as of 1990 Hypereutectic pistons were only made in the England and the United States*(source: pg 13 "How To Build Horsepower-Volume 1; by David Vizard).

More and more OEM pistons (if not all by now) are hypereutectic because of the advantages not only to the longevity/reliability of the engine but also to better exhaust emissions and a little more power to boot. But I'm sure there are still many aftermarket companies who have not yet changed over to this technology. So, the companies who have made this hefty investment usually advertise their product as hypereutectic. Although I've seen the term hypereutectic misused by many to describe eutectic alloys, I've yet to see it misused by companies describing their pistons.

There was a time when most cast pistons were actually hypoeutectic (less than 12% Si, often in the 7% range). Then manufacturers started making eutectic pistons and they marketed them as "high silicon" pistons. But as the eutectic piston became more ubiquitous, manufacturers began dropping that moniker and now they are known simply as "cast pistons." The same will surely happen to the term hypereutectic.

The telling info however would be the silicon content of the piston. If it is greater than 12.5% then it is hypereutectic. I can't find any info on the silicon content of NPR, Nakamoto, or Topline as yet. Anyone have a link to or a line on that info?

I'll second the partsdinosaur.com advice. I've gotten a bunch of things through him, and they're awesome if you're goin basically stock. They have performance, but not much for our setup. They have bundle discounts and sales at times also.

Is it true that you can't use the stock rods with JE pistons. I wanted the higher compression ratio and MB had said I could use stock because I don't plan on going to turbo or nitrous. Just was hoping someone can clear this up, heard both ways now.

you can, but you have to rebush the rod small end for a floating pin. With the price of the machine work, it's not really worth it. Just buy some cheap Eagles. They make an I-beam rod that's basically a stock replacement, and IIRC they're $60/rod.

WE do not have hyper-eutetic pistons.....I cannot stress this enough. We have eutetic pistons which are not the same. Eutetic is a name give to a cast alloy which relates to the type of melting point the alloy has.

A Eutetic alloy has a sharp melting point, that is, its melts at a given temperature and not a temperature range.

A Non-eutetic alloy does not have a sharp melting range and therefore has a plastic melting range, meaning as temp rises the alloy will begin to become weak till it evenually begins to melt.

A hyper-eutetic alloy is a eutetic alloy that has a melting point above the normal range for that alloy. In piston cases the allow is Aluminum.

Now lets apply this knowledge. Pistons are typically made up of Aluminum, Copper, gold, silver, manganese, nickle and silicon, prolly a few other substitutes. Now soft metals like Gold and Copper have no eutetic point because they are not eutetic metals. The aluminum alloy (conbined with sold metals to form the allow chosen) is combine with a percentage of Silicon. We know this because the amount of silicon determines the rate of heat expansion in our pistons. Typical content of silicon is under 20%. At 25% or more the piston greatly loses strength. The more Silicon a piston has, the less expansion the piston will have when heated. This is because Silicon expands less than aluminum. However, the more silicon you have the weaker the piston. At a melting point of a eutetic alloy, 12% silicon is all that will melt, the excess percentage will maintain a granular form in the melted alloy. The Reduction of Silicon is one way to create a Hyper-Eutetic piston. However, its not that simple, the alloy has a lot to do with it and silicon is not just there to regulate the Eutetic point of an alloy, the rate of expansion when heated becomes an issue which is why hyper-eutetic pistons are not good boosted application pistons. Dont over simplify the concept, alloy contents cant become pretty complex. If you add too much of a non eutetic allow such as Copper to an alum alloy, you will lower the eutetic value due to the non-eutetic properties of the combined alloy.

I dont want to try and go into chemical formulas and shit I really dont understand fully, thats just a small explanation of what Hyper-Eutetic is and Eutetic means. Our pistons are NOT HYPER-EUTETIC.

Its well know by engine builders that Hyper-Eutetics are not too hot for boosted applications anyway.

Hope this explains it a little, I am not the hottest at explainations.

Terry

Thanks for clarifying that. I was mistaken.

Originally posted by DarkOne
you can, but you have to rebush the rod small end for a floating pin.

Not necessarily. My shop has done two sets for me. No rebushing, just used the original rod and honed it out to a gauge fit. Drill an oil "splash" access hole and viola floating wrist pins. Didn't charge me for it, but that would normally run you around $50.

And no, no premature wear in this area. Took one apart at 9k of HARD miles. Then reused them in another engine. The other set has IDK how many miles. Hell, I just looked and I even have a third set in my "extras" box.

MB

Thanks for clearing that up guys.