What's the difference between Cast Piston & Forged Pistons?? - Ford Mustang Forum

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post #1 of 4 (permalink) Old 04-15-2003 Thread Starter
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What's the difference??

What's the difference between Cast Piston & Forged Piston? And which one is better? :p

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post #2 of 4 (permalink) Old 04-16-2003
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ccast pistons involved molten steel being pouried into a mold and then allowed to harden. Forged pistons are hammered into shape by use of a machine.

It's best to equate strength to a piece of wood: A piece of wood with a loose, wide grain pattern (equivalent to the cast piston) will be weaker than a piece of wood with a tight, close grain pattern (equivalent to a forged piston). The forging process actually hammers the individual steel molecules into a line and creates better strength than the haphazard placement of steel molecules in a cast piston application.

Go with forged, stay away from high-silicone content/hypereutectic, as this will not hold up very well under any type of mildly stressful situation. The best type of piston would definitely be a billet steel piston or Titanium piston, as these are machined to have extremely tight "grains" and are HUGELY strong!

Got N2O? Got a blower? GOt turbo? Go with forged AT LEAST!

My other toy is a '69 Mach I
351W, .060 over, heavy exhaust cam, straight pipes--approx. 325rwhp
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post #3 of 4 (permalink) Old 04-16-2003
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YodaFan is correct, but I think it depends greatly upon the intended usage (be realistic). As an extreme example...I built a 351W for a buddy of mine for his Super Street stock car with stock replacement '69 flat-top cast pistons. Ran 2 seasons on that motor with no problems. Engine is still together, waiting for a new "home". If you're only building a strictly street driven engine with no plans for regular "competition" use, I wouldn't be afraid to use a good quality cast piece. Forged is great if you've got the money and don't mind running a "looser fitting" engine. IMO...

I thought I wanted a career....turns out I just wanted a paycheck!

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post #4 of 4 (permalink) Old 04-16-2003
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Provided you're building something short of an all out competition motor, there's alot to be said for the current generation of high silicone "hypereutectic" aluminum pistons. They have almost the same thermal expansion rate as the cast iron blocks they run in and so normally exhibit better ring seal than a comparable forged aluminum slug which has to fit a bit looser in the bore to account for the large expansion rate difference between the piston alloy and the block. These pistons are also quite strong, and weigh much less than the old school cast or forged steel slugs Detroit used to use. Hence, less reciprocating mass and better throttle response. If you're building a blower motor, or a motor that will regularly ingest more than a 100 horse shot of N2O, or a wild street strip motor that runs 10.0:1 compression or more, than the added strength of a forged piston and polished or H beam rods and quality rod bolts is probably a good investment. In this case, the added peace of mind is worth some sacrifices in the area of ring seal. Otherwise, a quality cast hypereutectic piston will give your pony many miles of quality service.

John H

'66 candyapple red coupe, 347 4v engine, performer RPM heads and intake, 600 cfm holley carb, Sanderson short tube headers,
T-5, Versailles 9" w/ 3.50 gears and a detroit locker, 4 wheel discs.
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