Looking for a measurement

[My427stang]

Standard flat top/dish piston for 445.  Would like overall height of the piston at the skirt.  Not compression distance, looking to see how much variance in skirt length across manufacturers.

Diamond as a preference, but interested in any other brand too.  I already have some Probes here

Thanks!

(and thanks Brent for telling me I posted in the wrong forum)

[blykins]

I only have 4.250" bore size pistons here, but the compression height would be the same as a 445.  Overall piston height is 2.250".

[My427stang]

Thanks, was looking for overall height, wondering if different brands had longer skirts for more stability on the street.  So far, the Racetechs and Probes are about the same length, must be for clearance with the 4.25 stroke. 

[chris_r]

I have Mahle 4.080 flat top 445 piston overall height is 2.108

[My427stang]

Thanks, for those wondering, for a low rpm motor I was thinking the most stable piston would be best. Turns out they are all pretty much the same, likely due to clearance requirements more than use, although the Mahle is a little shorter than Diamond and Probe.

Thanks everyone, not a significant enough difference for me to spend any more time on it....    Good info though

[Barry_R]

Good info - but....There is way, way, way more to it than just the overall length.

Good skirt designs have a pretty significant amount of contouring in both diameter and taper.  Some will be putting the major loads across the pin boss and using the taper ends for stability, some will be using the diameter below the pin boss.  They use a fair amount of modeling to come up with growth patterns caused by temperature and I know that on OE stuff F-M was compensating for dimensional changes from loads way back fifteen years ago.

[My427stang]

Glad you chimed in Barry, any preferences on brands, materials, designs, etc for a long-running, quiet, light working 445 for a truck?  Will have about a 5200-5400 rpm ceiling

[Barry_R]

A lot of this dwells somewhere in the world of "good enough".  Numerous options are plenty fine for normal light use and will live a very long time.  OE stuff works on a different level, with some very different parameters.  So just because my history tells me to "prefer" one feature does not mean that other stuff will not work.

Probably a variation on 4032 with silicon for ring groove life - Mahle and Diamond both use that in street stuff.  I think Mahle may have the most advanced modeling capabilities for aftermarket stuff at this point - pretty hard to beat the resources available to an OE manufacturer just by virtue of scale.  No idea how much of that gets translated to their aftermarket stuff - but if you're gonna bet...  Guys like Diamond and CP probably focus most of their design efforts on the race side of their business as they should.  The Diamond street parts are very nice but fairly traditional in comparison to the creativity found in the race parts.

Between their own brand, private label, and Co-Fap stuff it seems like Mahle makes most of the rings in the aftermarket at this point.  Hastings has taken over the Sealed Power/Speed-Pro business.  Given their market position and OE capabilities I am pretty comfortable with the move to 1.0mm-1.0mm-2.0mm ring packages and volunteered to be an early adopter, and boy does it make for a smooth turning engine on the stand.  I still have customers that are worried about straying away from 5/16...

Mahle skirt coats everything, which is good insurance.  They also phosphate everything which I think might be a solution looking for a problem.  Some of the others have skirt coating standard, most have it as an option.  Seems like a bunch of factory stuff uses it now so it can't be a bad thing to have.

In short - I personally like my current Mahle parts a lot because they are a very modern package, but in a cruiser almost anything will work OK.  I prefer to stay with a forging simply because of the cost/risk/reward relationship.