Piston Advantages
 

Hey guys, I’m getting ready to put together a street cruiser 400. Approx compression is say 9:1, 3.55 geared and a TH350 with no stall. Car is used for cruising both city and some highway driving.

Is there an advantage in using one piston over another in this scenario between Speed Pro forged, KB Hypereutectic, or say Ross for this type of engine build? Will the weight savings be of benefit between these three options?

Thanks for your insight

Your first concern should be to step into the 1980s with a piston that does not use 5/64” wide (high friction ) compression rings.

Not following Steve, I don’t build engines for a living but assume that’s a dig on the KBs?

Having just completed an engine build, I had an idea of the piston I wanted, but ended up with a different piston because of build parameters. Depending on what parts you are using, you may be limited.

I ended up with DSS forged pistons. We wanted a Mahle that utilized a 1mm 1mm 3mm ring pack, but we couldn't get the correct compression height for a standard 455 4.21" stroke. If you can get the Mahle with the small ring pack, I think that's the piston to go with, but consult your builder.

I looked a bit and most of the KB stuff and the Speed Pro stuff still comes with the 5/64" ring lands.

That may limit you to pistons like Ross, DSS, Mahle etc.

I like to do as much of my own engine building as possible therefore TRW, Speed pro besides the weight and fat rings along with slotted skirt, press pin design are out of the question for me, if your in a pinch they fill the hole tho..

In the past i used Arias dont know if they are even in bizz anymore

my last build (433) got Auto Tech pistons from PK. pretty sweet units skinny rings slip fit pins drilled skirts

drilled skirts refers to area under oil rings TRW has a wide slot under ring better pistons have holes drilled here for oil migration and provide more skirt strength

Hey, is PK Paul K by chance?

Yes.

KB forged off the shelf since it’s a “street only” qualifier. Otherwise what the builder thinks is best.

Autotec 4032 alloy is what I used on my 434 build. You didn't specify if you need a dish or not, or what rings you want. The Autotec lets you spec anything you want for ring pack, ring placement, dish size and shape, pin placement, bore size, etc. If you can find a set of rings to fit the bore, Autotec can make the pistons to fit. Not sure who else does that.

I would not use a hypereutectic piston in anything. TRW forging is OK for a cruiser.

Auto tec from Paul K.Tom

I recently used Icon forged pistons from Kauffman.

Based on the options in the poll, I would bet there is a budget parameter here. Autotech has a good reputation for building what you need, but any custom piston isn’t necessarily going to be budget friendly.

I have been using Icon premium forged pistons on most of my 400/455 builds. Here are some of the benefits:
-They have a very good selection of both flat tops and dished
- They come std with a nice coating
-They use a 1/16, 1/16, 3/16 ring pack, not the most high performance, but very common with lots of options.
-They always seem to be the same size (diam) and weigh
Within one gram.
-Reasonable
No, I do not sell them, just have been very pleased.

My mild budget friendly build got the heavy, thick ring, press fit sealed power/trw forged pistons (no rings) for about $400. The higher performance larger budget build got DSS forged pistons (no rings) for just under $700.

Thank you Bill, this is the kind of information I’m looking for, I know nothing about ring packs weights etc so I am trying to learn. In a low compression street only cruiser is it worth nearly double the $ to go from Speed Pros or KBs? What are the gains?

Lack of knowledge of what is out there is why the poll does not contain all pistons. It is titled “advantages” which budget is always a consideration. Some of these pistons are twice as much as the old standards, but what do you gain in my application listed? Thanks for the reply Jason.

The ultimate street piston for a forged piston alloy should be a 4032 and not a 2618. The 4032 operates quieter, does not expand as much when hot, the piston to wall tolerances can be tighter, and the pistons will last longer. The ring lands will not wear as much either. The 2618 is stronger, more resiliant to deformation, and dissipates heat better. …not needed unless your past 600HP. The factory Speed pro forged are an alloy not far from being a 4032.

The thin 1/16 rings usually show gains of around 8 HP versus 5/16. The 1.5mm are closer to 10HP. Most the 1.5mm offerings have shorter skirts for less friction, and make more piston slap noise. Not all that friendly for street stuff. Modern pistons have skirt designs that offer advantages for friction. On a stock type street build it probably won’t change things much. On a max effort HP build the modern skirt design can be 30 or 40 HP.

On a stock street type build, having all the bells a whistles make you fell better. But if someone came in overnight and switched them out for old TRW slugs. I doubt you could honestly be able to tell until you went to a race track.

The engine I just finished we went with a custom piston, small ring package and short skirt design with a coating. One thing also done that I haven't experimented with before and really isn't talked about much is a longer rod setup. This is supposed to put less side load on the piston and provide a more stable piston at higher rpm with better ring control. It also does other things like more dwell time at TDC and stuff like that, which starts getting technical where discussions go on either side of the fence as to whether it's worthwhile. I was more interested in the stability aspect of it.

That makes some sense.

When costs are looked at, also look at if the piston is coming with a ring pack. As an example, my DSS pistons were a bit over $800.00, but came with the rings. The SpeedPro's may be around $400.00, but you're going to need to add rings to that, so the prices can start to narrow a little bit.

I will say that the previous engine build had the old TRW pistons in it. That engine still made great power even with a heavy piston and an old style ring pack.

I do think for a street only application where you may want quiet operation over anything else, a Hypereutectic piston is probably the best bet. You'd just have to know that if your plans for the car changed in the future, they may become a liability.

You guys still think Hyper pistons are a viable alternative? What about resistance to detonation and ring butting? Hyper pistons are high silicon content. They are dimensionally stable, but are brittle. Heavy detonation can crack them.
Some designs (particularly the KB hypers) tend to put a lot of heat in the top ring. In high power, nitrous or boosted engines, they tend to butt the top ring and tear the top of the piston off. They also cannot have dished milled in the top to lower compression. For a low compression, lesser than 400 HP builds, they would be an option. But if you get the bug for more HP, the hyper pistons quickly become a limiting factor to power production.

I used a set of Ross 2618 pistons in a long rod 400 nitrous street/strip motor. It ran for 10 years and about 15K miles. My only complaint was the piston slap when cold. Upon teardown, the pistons were good, even though the rings and bearings showed signs of being unhappy due to years of being run hard. The looser bore clearance makes some noise when cold and can shorten ring life. At least in 2004, the Ross pistons had limited options for customization. I sold those used Ross pistons to somebody here, they were still perfectly good.

Since I like to make the max power on pump gas and use nitrous, I have to use good pistons and rings. That 434 got the Autotec pistons and a $350 set of AP stainless LS style rings, torque plate honed, 6.8 BBC rods, the whole burrito. For a cruiser, the only pistons I would NEVER use would be a hypereutectic or the 8-eyebrow cast monster. Just be sure to consider the compression, camshaft choice, RPM range, gearing and risk of detonation with less expensive pistons and ring packs.