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Discussion Starter #1
How much play should a piston have once it's installed with rings?
This is on a 4.6 with forged internals so the rings are aftermarket am just not sure which ones it has.
 

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The shop manual spec for piston to bore clearance is -0.002" to 0.001".

This can be "sort of" measured with the pistons installed by using fine-wire gauges.

The ring end-gap specs are:

top compression ring: 0.005" to 0.011"
mid compression ring: 0.0018" to 0.0022"
bot oil ring: 0.006" to 0.0256"

There is no way to check the end gap with the pistons installed...
 

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Should you be able to move the piston side to side a bit or would that mean it needs new rings
It will move as much as the piston to bore clearance allows, which could be as much as 0.004" to 0.005" on a "built" engine. More than that means you need new pistons.

The rings "float" in their grooves in the piston and have nothing to do with piston to bore clearance...
 

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Discussion Starter #5
Ok because mine move a bit but the mechanic says that's how they're suppose to move due to them expanding because of the material the pistons are almost new with about 300 miles
 

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He is correct, the aluminum alloys from which pistons are made expand at a higher rate than the cast iron block...
 

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Discussion Starter #7
He also mentioned something about the rings being made for nitrous that also causes a little movement is that correct?
And thank you sir for all your help
 

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The rings have nothing to do with the piston movement--they float (are a loose fit) in their grooves in the piston. Then once the piston (with rings) is installed the rings are held in position by the cylinder walls and the piston is free to move about a bit because, when cold, its diameter is less than the cylinder diameter.
 

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He also mentioned something about the rings being made for nitrous that also causes a little movement is that correct?
And thank you sir for all your help
I bet the guy meant to say that the rings were gapped for nitrous. The ring gaps for nitrous motor would be slightly larger than they would for N/A motor. This is because more heat is generated while using nitrous and the rings would expand more. This is considering your motor doesnt really have some high strength rings for heavy nitrous use.

Either ways, as cliff said...rings have no relation to piston movement.
 
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