408W Mahle piston to wall clearance is good but also too much.... - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 4 Old 05-18-2017, 09:49 AM Thread Starter
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408W Mahle piston to wall clearance is good but also too much....

I put together my SCAT 408W short block and was wondering about piston to wall clearance. The kit uses Mahle #930255230 -20cc pistons. As per instructions after the cylinder was measured, the piston was measured .500" up from the bottom of the skirt and there is .0035" of piston to wall clearance. That is in spec according to the sheet. This was done without a torque plate or heads bolted on.

But when the pistons are at the top of the bore, the top of the pistons can be moved or rocked side to side by hand. If I move the piston to one side there is enough room to put a .020" feeler gauge in. I know pistons have a taper and are smaller on the top.

Is this normal with 1.300" comp. height 408W stroker pistons because the skirts are so short on the 2 sides and the other 2 sides that are inline with the wrist pin only have the thickness of the ring packages for stability?

Is the engine going to sound like a MAC truck and self destruct?


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post #2 of 4 Old 05-18-2017, 12:47 PM
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they tell you measure there because thats the widest point of the piston. for giggles measure the top of the piston. in short, your fine. keep on building. it has nothing to do with stroker pistons


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post #3 of 4 Old 05-19-2017, 03:29 AM
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The ring lands are .030 smaller than the skirt of the piston....and the skirt is tapered (not round either)

If the top land is .300 or over, the top is either tapered 3* or the top land is stepped in another .020.


We do it to confuse you.....
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post #4 of 4 Old 05-19-2017, 09:29 AM Thread Starter
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Quote:
Originally Posted by Mark O'Neal View Post
The ring lands are .030 smaller than the skirt of the piston....and the skirt is tapered (not round either)

If the top land is .300 or over, the top is either tapered 3* or the top land is stepped in another .020.


We do it to confuse you.....
At first I was concerned, especially after I tried to move the pistons in a stock 5.0L and they didn't move much. But no worries now after you and Woody confirmed what my reading told me. Motor is now assembled and is in long block stage.

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