I snagged these Mahle pistons at Summit's 'Open Box/Scratch & Dent' sale the other day for $400, intending to resell them. Part # MLE-SBC250040F05

Then I began thinking, hey... Maybe I should keep these for my motor. Not the BIG one I'm planning to build, I mean the stock one.
Quick and cheap rebuild... just recondition the stock rods, work the crank a wee bit and balance the whole thing, get a L.E. package and spray the hell out of it. Well, maybe not "hell", but definitely "heck".


But I'm a wee bit confused...
I looked on the applications page and it says the pistons are good for both a 3.48 and a 3.50 stroke crank. It also says 3.5 on the box itself.

Huh?

I know that's only two thousandths, but still...
EDIT: Ooops... that's TWENTY thousandths.

So what's the deal?

Either way, I could theoretically still sell it OR use it, although I suppose I may need a Scat 9000 or something similar in price. I just want to know what's up.

 

Yeah .002 difference or .001 difference in deck height... no big deal.

You could throw them in a stock motor and they would kick ***.

Bret

 

whats the piston to cylinder wall clearance tolorance on them?Thanks

 

i think your decimal is off, or am i reading this wrong?

 

Well, according to this here piece of paper I found in the box...


These pistons are made from a low expansion alloy which allows for tighter piston to wall clearance. We recommend you prepare the bore to exactly the piston size requested because the proper clearance is built into each piston for normal operation. (.0025-.0030 for SB and .0035-.0040 for BB)
Sever duty applications such as drag race, nitrous, forced induction, filled blocks or endurance racing may require an additional .001-.003 clearance.

 

Decilexaphobia is my clinical name for it. Lots of folks get it occasionally, even some of my closest relatives.

3.50- 3.48 =.020 stroke difference. But that only moves the piston .020/2 or .010 higher in the bore...which might not be all bad, quench-wise. Be careful how much you deck the block.


Sorry, BJB, had to do that.

 

I do like a tight quench. Like high twenties.

It occurs to me though...
I would have to buy rods to use these pistons and at that point I might as well buy a 3.75 crank, so I think maybe using these pistons myself isn't going to work out. I mean... why bother? Back to plan A I suppose... Sell 'em for a quick profit.

 

Yeah the old man caught me...

What will happen is that the piston will sit +.010" higher in the block so you don't have to deck it as far...

The 3.50" stroke is good in circle track stuff...

A 4.030" bore and 3.50" stroke give you a 357 cube motor, perfect for a 358 class...

Then on the rebuild you can hone it out .010", redeck the block and run a 3.480" stroke and keep the same cubes... works like a charm.

These pistons are setup for a 9.000" deck height and a stock block spec is 9.025" so you can see that a 9.010" deck height with the 3.50" crank is not a big deal.

Bret

 

you guys beat to it again....

 

Got it. Thanks Brett.