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B20 Piston Options

hensh_ma

hensh_ma

New member
Joined
May 20, 2024
Hey guys - need .020 minimum overbore pistons for my B20 build. Mostly stock with some headwork and a hot cam (either R or Tinus Tuning equivalent)

Any suggestions? I was looking at these at CVR and they seem to be way cheaper than the Mahle, but they're supposedly Silvolite which is a fairly reputable brand?
 
Budget: TBD, but relatively low. I'm not looking to build a $4K short block. Mostly stock bottom end with a shaved big valve B20B head with some porting. Hot-ish cam like I mentioned. Weber 45 DCOE.
 
Silvolites are barely acceptable stock replacements. I certainly wouldn't use them in a performance engine. Mahles have good metallurgy and chrome top rings but are only good to 6500-7000 RPM. Consider buying forged pistons if you want it to last and not have to worry about breaking ring lands.
 
@hiperfauto what do forged pistons cost? the internet seems to be all over the place for forged pistons for this engine...any recommendations?
 
If cast pistons can't spin past 6k, what the hell kind of casting does Honda use?
 
hensh_ma said:
If cast pistons can't spin past 6k, what the hell kind of casting does Honda use?
Click to expand...
Honda usually run a hypereutectic alloy that contains higher silicon content. They are also cast under very controlled conditions. Mahle uses similar metallurgy and some of the best casting techniques.

Forged aluminum pistons typically run between 550-750/set with rings. I used Traum for mine, and the quality was excellent.
 
Yeah. They’re super helpful if you call. They also have some good base designs for Volvo flat tops. Ring lands and expansion reliefs, gas ports, etc.
 
I know someone local that raced B18 and B20 cars regularly with mostly 0.040" oversize Mahle pistons.

From what I've seen Mahle, the forged pistons that KL, Skandix, and other European retailers sell, or custom is the way to go nowadays. For the rebuilt engine I'm about to fire up I went with Mahles, which you really have to go to Europe for if you need the first oversize. All I could find in North America about six months ago were 0.040".
 
Seems like Mahle generally runs north of $600 for a set. Custom forged, $800-900. Just got quoted from Traum, they’re in that range, and KL seems about the same after shipping. IMO the leap to forged from Mahle at that price point may make sense although it’s more expensive than I was expecting.

@cwdodson88 what would you recommend in terms of “tech” in pistons? I called Traum and he said to send him a piston for reference but wondering what to update from a 70-year-old technology perspective
 
Depends on what else you’re doing. If it’s just a street engine, there’s not really much needed. If it’s a 7500rpm race engine, there’s a lot that you could do.

Gas ports, not exactly needed on a street engine, but worth it on a race or turbo engine.

Skirt coatings- if you have it in the budget, yes, it’s worth it.

Larger gas expansion area, could be worth it.

Shorter compression height- requires a longer rod, but paired together can bring the rod-stroke ratio into a better area.
 
For a “stock” but slightly updated piston, you could possibly ask them to remake SN220191

They were stock ish, but slightly larger expansion area between top and second ring, and a little less meat around the bottom of the piston skirt for rod clearance.

These were for a 3.540 bore
 
@cwdodson88 appreciate it!

What were the build specs for that engine? Stroker?

Wiseco seems like another good option…but would need to go custom that route too
 
hensh_ma said:
Seems like Mahle generally runs north of $600 for a set. Custom forged, $800-900. Just got quoted from Traum, they’re in that range, and KL seems about the same after shipping. IMO the leap to forged from Mahle at that price point may make sense although it’s more expensive than I was expecting.

@cwdodson88 what would you recommend in terms of “tech” in pistons? I called Traum and he said to send him a piston for reference but wondering what to update from a 70-year-old technology perspective
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The Skandix/KL pistons are what you want for a daily, NA race engine, or low pressure turbo.

4032 forged piston, coated skirt, thin low tension rings, etc. I’d have to go back and see if they had lateral gas ports and a larger accumulator groove.

Edit: I went back and found the pics of the set I picked up for a race engine.
Accumulator groove, no lateral gas ports, and I don’t think they have forced pin oiling holes.
They are fully CNC machined on the underside though, and the finish level is CP/Mahle power pack level of detailed.

https://flic.kr/p/2q9KqLy
 
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culberro said:
The Skandix/KL pistons are what you want for a daily, NA race engine, or low pressure turbo.

4032 forged piston, coated skirt, thin low tension rings, etc. I’d have to go back and see if they had lateral gas ports and a larger accumulator groove.

Edit: I went back and found the pics of the set I picked up for a race engine.
Accumulator groove, no lateral gas ports, and I don’t think they have forced pin oiling holes.
They are fully CNC machined on the underside though, and the finish level is CP/Mahle power pack level of detailed.

https://flic.kr/p/2q9KqLy
Click to expand...
Those look sweet. They are KL? And Skandix supplies them?
 
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