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What pistons would you go with? 350 TBI

Discussion in 'The Garage' started by y5mgisi, Jul 25, 2005.

  1. y5mgisi

    y5mgisi 1 ton status

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    Doin the motor rebiuld in te 90 burb and m needing to make a choice on what pistons i should get. I can get some cheap ccast peices from a local pars store (knechts) for 10 bucks a piece But i want somthing a little beter quality that that. Id like to spend 150 or less on the set. It will be mostly stock with the exeption of a step up cam(yes i know tbi cam issue) and early heads and edelbrock performer four barrel intake, adjustable FPR and mabey headers. So does anyone have any recomendations as to what pistons i should look for. been finding good deals on ebay but dont know what to look for.
     
  2. Thunder

    Thunder 3/4 ton status

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    Federal mogul have always workd good for me. Proly best you can get for the price unles you go Hypereutectic. But those will cost more than you want to pay.
     
  3. LongIslander26

    LongIslander26 1/2 ton status

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    Pistons for 10 bucks apiece?

    Obviously, this is a job you want to do ONCE, and get it right the first time. A good short block assembly is the do or die part of the motor. You can cheap out and get the motor built, and then be doing it all over again alot sooner than you thought or wanted. There's no free lunches with stuff, and you get what you pay for. You buy cheap, you get cheap. I'd shop around and see what other responses you get from these threads. It's been awhile since I've had to buy pistons, but Federal Mogul, Kieth Black, and Sealed Power all make decent pistons for the money. Also remeber, if you're going to step up your cam specs, you have to step up your compression as well. Keep that in mind when choosing what kind of pistons to buy, as well as what brand.
     
  4. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I used KB silvolite (i think) flat tops and they were pretty good. All about the same size and weight which is saying something these days!
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Set of speed-pro hypereutectics I bought cost me $100. Bought those at a swap meet, was told by a speed shop that they could easily match that price.

    Just about anyone (FM, etc) should sell hypereutectic pistons, and they really are the way to go. Can't think of one reason to go with cast pistons anymore. Cost can't be much greater at all if hypers can be had for $100.
     
  6. leadvillek5

    leadvillek5 Registered Member

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    pistons

    go with kb silverlite 2 valve relief hyprestatic pistons or referred as claimer pistons. the best bang for your $.

    lancer
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Yep. Summitracing has both KB and SpeedPro Hyper's for $90/set.
     
  8. Thunder

    Thunder 3/4 ton status

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    Yeah get Hypereutectic pistons WOW the price on them has really come down since i last looked.
    Be careful using flat tops with TBI. Dont get your compression ratio over 9.5 or you will need chip work. 67cc heads and dished pistons will give around 9.2 to one. 76cc heads and flat tops will give about the same.
    What kind of "early" heads do you have?
     
  9. Mad-Dog

    Mad-Dog 1/2 ton status

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    Cast pistons are fine for most applications but you mentioned that you are using a set of "early" heads.
    What size chambers do the "early" heads have as this will dictate piston design for desired CR.
    Let's assume that you are referring to 76cc open-chamber heads and using the common flat top piston with 2 valve reliefs (-5cc), .039" compressed gasket thickness, .020" deck height (piston .020" in the hole, 4.030" bore (don't bore it +.060 without sonic checking the block), 4.060" gasket (you wont find a +4.030" gasket)........anyway this computes out tp 8.8:1 CR which is fine for cast pistons and 87 octane fuel, if you are more ambitious with installed compression such as using 70cc heads that will bring the static CR up to 9.3:1 then i would use hypereutectic pistons.
    For ships n giggles 64cc heads will produce 9.9:1 ........ :bow:
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    For close to the same price, why do you suggest cast pistons? Since the advent of hyper's, I can't think of one reason not to use them in the same application as cast.

    Cost I guess, but if $20 or so for far superior pistons when rebuilding a motor kills you, perhaps you shouldn't be rebuilding it. :wink1: Just kidding of course, but with a budget of $150, I see no reason hypers aren't the only choice.

    If OEM still uses cast pistons, its solely because of cost, not because of performance which is superior to cast.

    Cast pistons are to hypers as camel humps are to Vortecs. Just closer in cost and no downsid instead of the camel hump/Vortec difference.
     
  11. Mad-Dog

    Mad-Dog 1/2 ton status

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    Agreed, i have no grudge against hypereutectectic pistons but i would not use them for a stock rebuild even if cost was not a issue simply because it's a waste of money.

    My point is that cast pistons are fine for stock and mild applications and "hypereutectics" are a little better for a little more money.

    Whatever floats the boat....... :bow:
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    "Hypereutectic pistons (which are also cast) were introduced over a decade ago for OEM engines that required something stronger than an ordinary cast piston. Hypereutectic alloys contain a much higher level of silicon (16.5 to 18 percent versus 8.5 to 10.5 percent in a typical cast piston alloy such as SAE 332 or F-132). Silicon increases hardness for reduced ring groove, pin boss and skirt wear. Hypereutectic alloys are slightly lighter (about 2 percent) than standard cast alloys, and can be machined somewhat thinner to reduce overall piston weight about 10 percent.

    Hypereutectic alloys also handle heat better than standard cast alloys and undergo about 15 percent less expansion when the alloy gets hot because its silicon formulation rejects heat. Since hypereutectic pistons don't conduct heat they can be installed with somewhat tighter cylinder bore clearances to reduce ring flex and piston rock for improved sealing. Hypereutectic pistons that are made for performance applications may also receive a heat treatment to increase their strength; but how much is necessary is a subject of some debate. According to some sources, a "T6" heat treatment can increase strength up to 30 percent, but other engineers say this strength is not permanent: T6 is only stronger than T5 for the first 100 hours. A T5 heat treatment, on the other hand, gives a linear increase in strength over the life of the engine, which may be a better choice for many performance applications.

    Many late model engines today come factory-equipped with hypereutectic pistons. In many instances, the OEM hypereutectic pistons can handle engine modifications that boost power up to 30 percent or more over stock. Aftermarket hypereutectic performance pistons are available for upgrading a wide variety of engines including SB/BB Chevys and Fords, as well as many late model engines and sport compact engines. Some racers are using hypereutectic pistons successfully as a lower-cost alternative to forged pistons on circle tracks and drag strips.

    One manufacturer said hypereutectic pistons can usually handle up to 1.5 to 2 horsepower per cubic inch of engine displacement. Beyond 2 horsepower per cubic inch, they would recommend upgrading to forged pistons. The manufacturer also said its hypereutectic performance pistons may be able to handle up to 1,000 horsepower provided the fuel mixture and timing are correct so the engine doesn't go into detonation or preignition."

    Automotive rebuilder

    10% less weight, 15% less expansion. Those aren't small numbers. Can't find anything that equates that to power production exactly, but both of those decrease engine wear, and thats completely ignoring all other benefits of weight reduction, tighter tolerances, and heat rejection. Like I said, with those benefits, for $20, I'm surprised cast is still around.

    I don't know, I guess if going for absolute budget build, the $20 difference over cast could be seen as a waste.
     
  13. Mad-Dog

    Mad-Dog 1/2 ton status

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    So for $20 more the pro's far outweigh the con's......... :bow:
     
  14. y5mgisi

    y5mgisi 1 ton status

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    Wow good replies sorry i havent had time to check back on here been kinda busy you know any how the hypers are deffinetly going to be the way that im going. The heads are number 3998993 GM 38(mortec says 72-73, 307-350 75cc Also are the goodrench crate motor heads it says)...Does anyone know if these heads are better than the stock 90 suburban 350 heads? Also i think im going to make the leap and run the 400 crank. What all needs to be done in order to get that to work? turn down mains, clearence block, 400 flexplate and balancer, what about rods and pistons do i use 400 rods with 350 pistons? And yes i know about fuel injection issues but i dont think its anything that cant be handled. So the current plan is to do....



    • 400 crank with wich ever rods and piston combo sounds best(ballanced)
      moly rings
      the early heads with stock rockers and valvesprings.
      edlbrock performer intake
      670cfm throttle body w/ flowmatched 350 injectors, adj, FPR
      throtle body to carb adapter plate
      what ever the first step above stock cam is that i can use with the tbi(sugestions please)
      stock exaust manifolds ith single 3" with flowaster and no cat.
    What do you think ? anything you would change? anything im missing
     
    Last edited: Aug 3, 2005
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    Are the heads done? I'm sure the older heads are better flowing pieces than the TBI swirl port heads, but if you haven't done work with them, and you have money, I'd seriously consider stepping up to some good aftermarket heads. Flow is one thing, but overall design needs to be looked at, and newer aftermarket heads are better hands down. I think around here a complete head rebuild with "standard" valves and springs is right around $300. Something to figure in if you can find aftermarket heads.

    Approx. compression ratio of 9.2:1 (perfectly fine on 87 octane with better design heads) is very easy to achieve with off the shelf 64CC heads, pistons, and head gaskets.

    Of course that's all personal preference and how much you have to spend, but of course, throwing unrebuilt (or cheaply done) heads on a new motor is just asking for problems IMO.
     
    Last edited: Aug 3, 2005
  16. 1977k5

    1977k5 3/4 ton status Vendor

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    There is very little machine work necessary to make a 383 work, mine just took a little grinding on one of the rods (I think) before it went to the balance shop. Balance is a must on a 383, and is cheap and worthwhile on any motor IMHO. Keith Black hypereutectic pistons are very good and relatively inexpensive and probably a good way to go (that's what I have in mine, and they survived dropping a valve). As far as rods, have the rods in your 350 (5.7" rods) reworked and use those. I think the most cam you can use with a stock TBI system is around 200 duration@.050. My guess is the early vortec heads from your stock suburban are better than the heads you listed in your post. More stuff to think about, but the L31 vortecs will make you a lot of power and are cheap (a little over $500 a set, and you are already planning on buying a new intake manifold). If you are going to use the old heads, have the valve seats redone and use new springs that can take the lift your cam will have.
     
  17. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    If you are going stroker it is hard to beat powerhouses kit. Sometimes it can get expensive to balance so for less than 700 bucks you get the whole rebuild kit balanced (of course have your local machine shop check) new balancer and flywheel etc. Good deal I know a couple of poeple that have these powerhouse kits in their trucks both of them cheaped out on heads and the engines still make decent power. With TBI you have to watch compression as was already stated and your cam if you get aftermarket heads you will have to get a new chip there is some good info around on how to do this yourself though for a couple hundred bucks If you go the 383 route let me know how it goes I might be able to get a TBI setup for cheap and my next engine will be a stroker
     

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