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In 1996, Ford switched over to thinner metric piston rings 1.50mm x 1.50mm x 4.00mm (for lower friction?) for all 5.0 including F150 & my 1996 Explorer 5.0 which is going in my 64 Falcon. All 302 up to 1995 used the 5/64" x 5/64" x 3/16" piston rings. The only difference that I can find is the compression distance. The metric piston with 1.5mm piston ring has compression distance of 1.595. The standard piston with 5/64" piston ring has Compression Distance of 1.599.

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Speed-Pro Hypereutectic Piston and Ring Kits (5/64" x 5/64" x 3/16") $170:
Speed-Pro Piston and Ring Kits Z8KH273CP30 - SummitRacing.com


Speed-Pro Hypereutectic Pistons (1.50mm x 1.50mm x 4.00mm) $118:
Speed-Pro Hypereutectic Pistons ZH816CP30 - SummitRacing.com

+ I need the rings:

Sealed Power Plasma-Moly Piston Ring Sets ZE458K30 $71:
Sealed Power Plasma-Moly Piston Ring Sets ZE458K30 - SummitRacing.com
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Is it going to make any difference if I use the pistons with the 5/64" or the 1.5mm piston rings ?

Is it safe to assume that the rotating assembly with 1.5mm x 1.5mm x 4.0mm rings is "lighter" than the 5/64" ?

I would think it would balance out better with 1.5mm rings & pistons which is what my motor came with originally.

Once I go 0.030” over, do I need to have my rotating assembly re-balanced ?

The old 302 pistons & rings kit is $170. For 96+ 302’s with 1.5mm rings, there is no kit and must purchase pistons and rings separate but he cost is only $20 more at $190.

My Mustang book lists the piston-to-bore clearance for a 1979-1987 to be 0.0018"-0.0026" and for 1988 on, the book lists 0.003" to 0.0038" (forged pistons ?). For the 96+ 303, the piston-to-bore clearance is tighter at 0.0012"-0.002".

Thanks

Waid
 

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Is it going to make any difference if I use the pistons with the 5/64" or the 1.5mm piston rings ?
While you can use either in your build, the metric rings are a bit more efficient and give longer bore life under normal conditions.
Is it safe to assume that the rotating assembly with 1.5mm x 1.5mm x 4.0mm rings is "lighter" than the 5/64" ?
I would have to do a lookup, but I believe they are the same balance spec but slightly tighter tolerance.
Once I go 0.030” over, do I need to have my rotating assembly re-balanced ?
For 'normal' operation at rpms at or near stock - no. Precision balancing for performance applications is usually a good investment. Note I say precision, as a production balance job will be of little or no improvement. Precision balancing improves engine power capability, longevity and reliability at high rpms by reducing added stress.
My Mustang book lists the piston-to-bore clearance for a 1979-1987 to be 0.0018"-0.0026" and for 1988 on, the book lists 0.003" to 0.0038" (forged pistons ?). For the 96+ 303, the piston-to-bore clearance is tighter at 0.0012"-0.002".
Yep, they keep improving the piston materials and reducing expansion for better stability, improving seal by reducing rock, while improving hot strength. This is the other improvement that goes with the rings. Stick with the tighter tolerances unless building for high piston heat with N2O, boost, extreme rpm, etc. If building a hotter engine, then the ring gaps must be adjusted for expected expansion as well. Always verify the piston manufacturer's bore clearance spec's, in-case they are using a different material than stock.

David
 
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