Will these v6 pistons work?

Discussion in 'Small Block Tech' started by tubecatgs, Jul 8, 2017.

  1. tubecatgs

    tubecatgs Finally a 4 speed......

    I have seen a few people say that Buick v6 pistons will work in my 350. TA high compression pistons at .040 over are backordered until September. If I need .040 pistons, will either of these on ebay work if I can get 8 of them? Will these v6 pistons give me high compression in my 72 350? and will they work with existing components such as rods? Anyone see any issues? its a mild build shooting for close to 300 HP. thanks

    http://www.ebay.com/itm/Silvolite-P...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

    http://www.ebay.com/itm/Set-of-6-Ca...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

    thanks
     
  2. sean Buick 76

    sean Buick 76 Buick Nut

    Yes I have used them with good results. They give about 10.5:1 compression or as high as 11:1 depending on the combo. I know one by who ran 12s in the quarter using these pistons.
     
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  3. MrSony

    MrSony Well-Known Member

    with stock deck height? what thickness gasket?
     
  4. gorehound

    gorehound Gold Level Contributor

    Can these be used with stock 350 rods?
     
  5. alec296

    alec296 i need another buick

    Yes the 3.0 v6 Buick century piston is a direct fit for a Buick 350 . Stock rods and all. They sit .090-.100 below deck for about 9.8-9.9 compression with .043 head gasket. Sitting that low does give up a few ponys but the Pistons are cheap.
     
  6. sean Buick 76

    sean Buick 76 Buick Nut

    my setup used 40 thou head gaskets and the heads were milled a bit. Stock deck height and mine worked out to 11:1. Yes they work with stock rods.
     
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  7. 8ad-f85

    8ad-f85 Well-Known Member

    Sitting .090-.100" below deck with a thick headgasket isn't losing any power as long as the appropriate compression is there. It's well away from any quench action that would contribute to increased energy release due to enhanced mixture motion.
     
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  8. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Yes those will work, as well as any other Buick v6 (3.8 or 3.0) piston available. Same bore, same pin diameter, acceptable compression height (over 1.8). Just need to get 8 instead of 6, which of course could be any combination of getting a set of 6 and adding 2, or buying 8 individually. Getting a set of 6 and then buying 2 individual pistons would be the lesser expensive route.
    The flat tops are cheapest since there's no extra machining to create a dish.
    Here's a set of pistons I don't see suggested here often, which are an 'in-between' compression piston, better than the '8:1' sets you see available.
    These pistons could be called '9:1' pistons with little milling of the deck and heads.
    Maybe not what you'd want for your combination, but I'm listing them in this thread because of the relevance.
    CH is 1.805 and dish is 12 cc (I did the math on dish displacement). Feel free to double check me.

    https://www.summitracing.com/parts/uem-1736-040/overview/

    These pistons (among most other v6 offerings) come in various sizes too, ranging from standard to .020, .030, .040, and .060 overbores.

    Other deep-dished KB cast piston replacements I see listed tend to have a dish size of 24 or 25 cc (!), so those are pretty low comp, especially if you do no machine work to the block/heads. We're talkin' around 7.5:1 lol. The pistons above math out to about 8.5-8.75:1 with no machine work, depending on how thick your deck is.

    Just an FYI
     
    Last edited: Jul 9, 2017
  9. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Quick question for you: would the flat tops disadvantage the Buick 350 because of the lack of a dish? Wouldn't it decrease the fuel/air charge's swirl effect due to no dish, and/or decrease the centralized flame travel?

    Maybe not enough to matter, but I wanted to get your professional opinion on this.

    Thanks!
     
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  10. alec296

    alec296 i need another buick

    I do believe that no dish will affect swirl and the "tornado " affect of the design. But with it being so low below deck the cylinder wall is basically the combustion chamber now . Most machinist I have discussed with would prefer zero deck or no shorter then .040 below. Being as how these guys build straight 6 and v8 over 1000 hp constantly, they also posted this figure.
     

    Attached Files:

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  11. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    The cylinder walls are part of the combustion chamber regardless. The full effect of the combustion doesn't happen while the piston is sitting at TDC, it still continues to travel with the piston as it's being driven downward below deck. More of the cylinder wall would be exposed during this process with it sitting farther down below deck at TDC, sure.
    Without a closed chamber head, it doesn't really matter where the piston sits below deck, which is relevant to the Buick 350's inherent design, and not other engine makes that make use of a quench platform. The narrow bore helps offset this on the Buick 350.
    It then becomes a matter of where you want your pistons to sit in relation to the compression ratio you're seeking to achieve.
    On mild-moderate engines, I don't really think getting everything perfect is going to make or break the combination's efficacy, and is always best to err on the conservative side when pump gas is going to be used. The power is going to be in the heads anyway.
     
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  12. gorehound

    gorehound Gold Level Contributor

    I'm sorry I don't mean to be hijacking the thread. I'm interested in the V6 pistons in order to get more compression for a Crower level 3 without any machining to the heads or block. Is it worth it or even necessary for this cam? Also if I were to go that route I notice a lot of these on Ebay have the part number +.020 or.040. I am assuming this would be if the chamber was bored you would order the piston to mach the bore so if I had bored .020 over for some reason I'd want the .020 version?
     
  13. 8ad-f85

    8ad-f85 Well-Known Member

    Could go either way? :)
    I'll start tests knowing your check is in the mail.
    If I see a useful correlation favoring either direction and under certain specific parameters...I'll keep that for my own benefit and release a smidgen of info satisfactory to appease the checkwriter, or just enough of a written conclusion to prevent the general public from benefiting from my brain work until contracts are written and potential monies protected for sole exclusivity (sarcasm, sort of).
    (professional opinion taken with a grain of salt here, as very few are deriving income from this forum or being paid to build someone's engine)

    Good question though, allow me expose more layering, because...carrying vaporization effectivity all the way to combustion can be tricky and mostly beyond our ability financially as either hobbyists or whatever to explore.
    One thing grossly missed with typical forum discussion is that swirl and tumble mixture motions prior to combustion are both subject to a narrow rpm range of usefulness as well as overshadowed by other operational aspects competing with various point of diminishing returns metrics as they contribute to the overall package.
    An example would be taking a fast swirling port and drastically changing it's rpm range or cylinder size.
    It doesn't do any good to surpass diminishing returns on that effect if the port chokes out or if you spin the fuel out of suspension.
    Weird things can happen near the squish zone too, so there's that. How much can you pay a porter to influence or balance these things? Not economical.
    This is only the beginning and not worth too much commentary.
    Easy enough to test with a couple of short blocks and top ends.
    I doubt there's enough accurate info on this forum or publicly shared specific to this engine to confidently stand firm on any answer.
    I would think at low power levels we'd all be arguing about things like 7hp or .3 compression increases that would never show up from one person's car to the next as a notable improvement. Lost in the forest. Or quagmire.

    My comment above was coming from the notion that this engine is being speculated already out of the danger zone of detonation due to quench distance and is slated for a smallish cam, which would be a concern for detonation (even though many have been built with more cylinder pressure...it can't be a blanket statement that they ALL can survive it with as many environmental variables specific to each project)

    Much discussion and recommendations suggest miniscule increases at the cost of machining that may not be needed, or that could have unintended consequences such as problems with detonation.

    The quick answer is...more questions!
    4(?) hp loss due to dish pistons centralized burning and pressure attributes?
    Made up by reversing piston offset? (can't recall if possible on these...)
    Power loss due to inability to tune timing curve due to det. problem?
    Overcome by wider exhaust valve seat cooling hot valve or a lower than recommended thermostat?
    Intake manifold heat used?
    Would any of this be noticed in a non-optimized car?
    Notice I defer to reducing machine costs, even though I'd be making more $$ if I were doing it...
    Thanks for the quick question, Gary. Geez. :) :) :)
     
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  14. alec296

    alec296 i need another buick

    For your build the Pistons will work fine. So yes. Use them. The crower cam will work on a lower compression piston but seems to like 4 degrees of cam timing(advance keyway on timing sets). But with the possibility of being at almost 10 to 1 I would go with 4 retarded on the cam as the compression will make up the low end and you want to bring the dynamic compression down alittle for pump gas. I would suggest getting cam degreed for sure. Yes slightly more technical stuff.
    Again yes the Pistons and cam are both good for your engine. Yes the .040 is cylinder overbore specs so if your overbore is .040 that's what piston size to get
     
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  15. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    haha

    Well alrighty then! Seems the 'quick answer' can be summed up as: it doesn't really matter, not on combinations such as these...

    Thanks, Tony. :)
     
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  16. 8ad-f85

    8ad-f85 Well-Known Member

    The strong preference for zero deck or quench <.040" is for engines that have a quench pad in the combustion chamber.
    Tests with a specific chamber shape on another brand of engine show a 10hp(?) increase for every .010" less clearance.
    Possibly Vizard shared that one, don't remember the details.
    The engine discussed here isn't using quench as a cooling action prior to combustion, or to increase the tolerance for cylinder pressure via compression.
    Traditionally, swirl is accelerated as the piston rises, but only seeing it's peak effectivity below appx. 3500rpm.
    Much of this is read as study for engineering students. It takes serious equipment to accurately measure many parameters of combustion and it's events.
    What most do is work with specific features as they apply and to their specific limits, rather than test the individual attributes for their own merit.
    (I'm not seeing the msgs as they update, apologies if things get skipped.)
     
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  17. 8ad-f85

    8ad-f85 Well-Known Member

    Interesting thing about the diagram showing the dome vs. flat...the dome could be close enough to contribute some squish velocity and quench action to the events.
    The SBB could be built to take advantage of this with heavy head milling and/or a piston that exceeds the deck.
    The subject in general touches on things that have interesting effects at double the power output.
     
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  18. Gary Farmer

    Gary Farmer "The Paradigm Shifter"

    Indeed.

    While we're stirring the pot, how about considering the extra 12 CID added from that huge 25cc dish (over 1.5 CID per piston) from the low comp pistons, then 10 more cubes from a .060 overbore (totaling 372 cubes)...if one were to zero the deck and get a half ways decent compression (9:1, say), then add in the fact that the valve timing events occur as such that a high dynamic compression (for use with 93 pump ethanol flavored fuel) is achieved with this 9:1 compression, adding in the extra swirling effect this massive dish would achieve using a cam that's about petered out by 3500 RPM anyway, a respectable, highly efficient grunt engine could very well result.

    lol
     
  19. MrSony

    MrSony Well-Known Member

    lol I had those KB hyper pistons. Motor sounded cool. No wonder it loved 87. That dish was massive compared to the pistons in my SP motor.
     
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  20. 8ad-f85

    8ad-f85 Well-Known Member

    While we are at it why not go another .015" for some chevy 283 pistons and contour the dome similar to a 2 stroke yielding a 14:1 chamber on E85, solid fill the block, mill off the top of the head on the intake side in order to reconstruct a 1" higher port that can keep the airspeed up along with the cfm requirement and see if it will match the torque/displacement ratio of a typical Engine Masters entry. Since half the head will be new stock we can adapt a 1.8 Nascar rocker setup that can maintain the seat events of the stock cam.

    lol
     

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