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Author Topic: Forged v. cast pistons  (Read 589 times)

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Offline dodgerc88

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Forged v. cast pistons
« on: March 11, 2012, 10:11:58 PM »
I am planning an engine rebuild for my 88 RC w/318 and was wondering if anyone can answer the forged v. cast piston question for me. What are the pro/con for each? And I am also wondering what is the best Carb/Intake compromise for street and offroad use?
84 D-100, Slant 6  (traded for RC)
85 D-150, 360 w/ 318 heads and carter 4bbl  (sold)
88 RC, 318, 727 and 410 rears 
92 S-10 Blazer (fixed it up and traded for 'rango)
00 Durango, 4.7l  32" Geolandar AT/s
 
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Offline ToxicDoc

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Re: Forged v. cast pistons
« Reply #1 on: March 11, 2012, 10:22:42 PM »
Forged if it'll be severe duty, forced induction, turbo etc.  Older cast is weaker, but modern cast (hypereutectic) is pretty formidable.  The cast expands less so the bore-to-piston gap can be tighter.
'85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

Offline Captain Obvious

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Re: Forged v. cast pistons
« Reply #2 on: March 11, 2012, 10:33:21 PM »
There are some pluses for cast. GM loves to use cast even in 500hp with forged or titanium rods, so that says something.

Reason is less emissions and slight power increase due to a tighter bore. Cast doesn't expand so much , so they can run a tighter better sealing bore.

Since the forged requires a looser cold tolerance, they slap more until they warm up and seal.

They can handle higher cylinder pressures, but very few truck builds make those kind of pressures. Lot of vehicles come from the factory these days, including trucks, with 400hp/10:1CR+ and cast pistons.

In between the 2 are various grades of hypereutectic cast, and usually sufficient for all but the 1%'ers.

Offline cragdweller

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Re: Forged v. cast pistons
« Reply #3 on: March 13, 2012, 08:49:36 PM »
Don't forget detonation resistance...forged being better.
1975 Plymouth Trail Duster Sport.  440/727, 203/205 doubler, Dana 60 front and 70 rear.  Still under construction...

1977 Dodge Power Wagon W200 Crew Cab.  Next project.

2002 2500 Quad Cab Short Bed 4x4.  Cummins HO w/ NV5600 six speed.

Offline Gohot

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Re: Forged v. cast pistons
« Reply #4 on: April 11, 2012, 06:22:47 AM »
It's sort of MOOT as there are only a couple good pistons for the 318. For performance the usual Keith Black 167's in flat-tops. Everything else is just Daily driver stuff and ordinary.
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Offline cragdweller

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Re: Forged v. cast pistons
« Reply #5 on: April 11, 2012, 09:17:47 PM »
For a 318, go with a nice set of KB hypers.
1975 Plymouth Trail Duster Sport.  440/727, 203/205 doubler, Dana 60 front and 70 rear.  Still under construction...

1977 Dodge Power Wagon W200 Crew Cab.  Next project.

2002 2500 Quad Cab Short Bed 4x4.  Cummins HO w/ NV5600 six speed.