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cast vs. forged pistons

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by solowookie, Dec 31, 2001.

  1. solowookie

    solowookie 1/2 ton status

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    ok guys...

    here is my question; I've got 2 master kits I am considering for my engine rebuild, and one has cast pistons (about $200 cheaper), and the other has forged pistons.

    what are the benefits to the forged pistons, and why would I spend the extra $$$ on them? (ok - now a little more back ground the forged pistons have a 10.0-1 ration, while the cast have a 9.25-1 ration and I'd prefer the 9.25-1 ratio so I can run the cheap stuff in it if I want to)

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  2. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Forged is stronger, sometimes lighter, and has the added benefit of being able to take NOS much better than Cast pistons. If I had to get a kit, I would buy forged for sure. As for the higher CR - just look around until you find the right CR for your motor.

    I like <a target="_blank" href=http://speedomotive.com>speedomotive.com</a>. They seem to have a good selection, and can help put together a kit for you at an affordable price.

    <font color=red>GOT MUD???</font color=red>
    My license plate reads:<font color=blue> 8 YR SUV</font color=blue>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s - 36" TSLs
     
  3. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Forged pistons expand more when they get hot so they are made with more clearance when cold. Because of this, they can sometimes be heard rattling when cold (sort of like a diesel). I have also been told that because of this, you should let the engine warm up before driving (or at least take it really easy) so that you don't have as much piston slop. I've never run forged pistons though so I can't say for sure. Personally, I doubt I would run them unless I was going for forced induction and/or NO2.

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    The stock pistons are cast, but they typically only last 150,000-300,000 miles. [​IMG] Forged pistons are good for severe duty applications, like forced induction, nitrous, etc. Midway between the two in strength are hypereutectic cast pistons. They have a higher amount of silicon blended with the aluminum, which makes a much harder alloy.

    Check out <a target="_blank" href=http://www.federal-mogul.com/speedpro/index.html>www.federal-mogul.com/speedpro/index.html</a> for lots of good piston info.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  5. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Harry - that is some great info on pistons! Good find!

    <font color=red>GOT MUD???</font color=red>
    My license plate reads:<font color=blue> 8 YR SUV</font color=blue>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s - 36" TSLs
     
  6. RedDwarf

    RedDwarf 1/2 ton status

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    Solo, you don't really want FORGED(sorry) pistons unless you are going to be reving over 5000 RPM with regularity.

    Street/mild engines are better off with the tighter-fitting hypereutectic pistons for the above mentioned reasons.

    If you do get forged, I recommend TRW or Weisco brands.

    <P ID="edit"><FONT class="small">Edited by RedDwarf on 01/01/02 03:23 PM.</FONT></P>
     
  7. rusty79

    rusty79 1/2 ton status

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    i happen to like keith black pistons as well just my 2 cents its what i have in my motor(yet to be fired and a friend had them in his camaro worked well especially seeing how he drove the car)

    Rusting away in VA
    Hey it almost runs!
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    &lt;quote&gt;
    Solo, you don't really want cast pistons unless you are going to be reving over 5000 RPM with regularity
    &lt;/quote&gt;

    Don't you mean "forged"? [​IMG]

    Russ

    85 K30 CUCV, 350 TBI, TH400, 205, D60/C14, 4.56 Locked
    Some day: 4" lift, 44" tires, massive cutting, shorter wb and rear overhang.
     
  9. solowookie

    solowookie 1/2 ton status

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    hey guys I agree there has been some pretty good info here! I think I've been able to find what I intended too... [​IMG][​IMG]

    I've got a few different master kit's that I'm looking at, but haven't really decided on one.

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  10. Thunder

    Thunder 3/4 ton status

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    I agree with Harry about the hypereutectic cast pistons. I think they are the best for all around performance/stock applications.
    Forged really need only be used in high performance high rpm/load engines. They are a unessary expence for a low reving truck engine.

    Silvolite are my favorite pistons here is a Link that has a lot of piston info, how to stuff, comparisons, ect. <a target="_blank" href=http://www.kb-silvolite.com/1toc.htm> KB-Silvolite Piston info</a>

    <a target="_blank" href=http://coloradok5.com/gallery/Thunders-Blaze> Blazer pics</a>
     
  11. HarryH3

    HarryH3 1 ton status Author

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    My 383 has the Silv-O-Lites in it. Had to go with the mongo dished ones to keep the compression ratio reasonable with the small chamber L98 heads.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  12. CaptCrunch

    CaptCrunch 1/2 ton status

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    Either the Speed-pro or KB silverlite Hyper's would be nice for a street motor. When the money is on the line though I'm with JE all that way.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>
     
  13. NoRulz

    NoRulz 1/2 ton status

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    kinda off topic here, but the thread seemed semi-appropriate. Does anyone know who makes Trick Flows pistons? Thinking about building a stroker, &amp; they're one of few places I've found that offer a stroker piston for what I'm thinking of doing. Thanks in advance.

    My Ford has chevy parts! it's all good!
     
  14. CaptCrunch

    CaptCrunch 1/2 ton status

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    Trick Flow is their own brand. They are most commonly associated with Ford cylinder heads, but have also expanded to additional applications and some additional engine parts. Personally I'm not a huge fan, I had street heats on my old mustang gt back when it was my thing. They had a problem wioth their assembled heads dropping vavles a while back, but the bare castings were awsome.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>
     
  15. Twiz

    Twiz 1/2 ton status

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    I think (guessing) Trick-flows are a Summit raceing thing.
    Summits, or addvertizments for Summit are the only places I've seen (that I can remember) that had Trick-Flow stuff. Don't know much more than that about them. Anyone else?

    As far as the Cast -vs- Hypers -vs- Forged.

    -Cast pistons are cast of aluminum. fine up to 4500 RPM, normal use, basic rebuild. Nothing is wrong with going cast, as long as the RPM is kept low.
    -Hypereutecticss are also cast (poored into a mold) but with more silicone added to the mix. More silicone, than can be normaly diluted into the aluminum, so thats where the "Hyper" comes from. Silicone makes the pistons stronger. Hyper-pistons are stronger than cast pistons, but a step under the Forged pistons. Probably good to 6000 RPMs (guessing). One thing to note, Hyper pistons (atleast Kieth-Blacks) need the top ring-gap widend. On the pistons I have (K/B) and the top ring is closer to the top of the pistons than the cast ones that came out of the engine. So, the ring gets hotter, and therefore need a wider ring gap. I've also heard somthing about how Hypers conduct more heat, or refelct more heat... something like that... too. Thats something to research if your tring to get the max compresion without detination. I'd like to know which way that goes (absorbs heat, or refelcts heat) if someone knows.
    -Forged pistons are compressed, out of aluminum (?) not poored like the cast/hypers. They are good for just about anything, I'm sure top-fuelers use Forged pistons, if that tells you anything about how stong they are. They do rattle when cold.

    Go with cast pistons if it's a driver, and won't be abused. Save some $$ when you can.
    Go with Hypers if you plan on slapping it around some. Thay would be able to take the abuse, and then some.
    Go with Forged if you add Nitros or Supercharge it, or spin it hard, or need a custom set of pistons (like, for example a 327 with a 6 inch rod- anyone know where I can get a piston for that combo?)

    <font color=blue>Wow Factor
    A SBC at 6000 RPM, Piston speed of 60 MPH.
    3- The intake charge reaches a speed 4 X greater than the piston.
    Thats 240 MPH.
     
  16. solowookie

    solowookie 1/2 ton status

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    thanks twiz... good info! [​IMG]

    got the pistons out of the block etc... the pistons are showing some where, but the bearing wear isn't too bad. they bearings need replaced, but the engine doesn't look like it was abused, and they don't indicate alignment will be needed!

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  17. mpascino

    mpascino 1/2 ton status

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    Do you think I could run a 6 psi Supercharger while running 10.5 hypereutectic pistons or is that signing my own death wish?
    Mike

    The jeep eater ......[​IMG]
     
  18. HarryH3

    HarryH3 1 ton status Author

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    I think your compression ratio is too high to start playing with superchargers. [​IMG] 10.5:1 is one the ragged edge of detonation problems already. 6 PSI would put you over the top.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    One other things about forged is that they do not have an insert in teh head of the piston...that means more expansion and contraction during normal use with a forged piston. I checked TRW's site out, and they didn't mention that at all, but in one of my engine building books, they showed the insert used in the cast pistons, which is one of the reasons they don't exhibit as much expansion/contraction as the forged. I'm not sure if the hypereutectics use the same insert, I haven't heard much about them, except for what was on the TRW site. Doesn't look like there is a reason to go cast if hypereutectics are about the same price.

    FWIW, I don't think GM used forged in any of their "truck" motors, stock, yet TRW shows forged as being a good choice for light duty trucks. I don't think I'd agree.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     

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