Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

Piston bowl shape?

Discussion in 'V6 Development And Modification' started by 2seater, Jan 7, 2018.

  1. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    By way of introduction, I am in the U.S. and work with the Buick 3800 in a Reatta. The specific reason I am asking here, is the almost total lack of information on the Holden 3800 on my usual technical forums. I reckon the proper place to ask is where there is the greatest knowledge base.
    This started when I was looking through a Silvolite piston catalog for possible shelf stock pistons to use for my next build. I found 1751H which is listed as for a '97-'04 Commodore but no other model detail. The bowl shape with the raised island in the center made me wonder what the purpose is? The .905" offset pin and 1.449" compression height would be about zero deck on my 9.5" deck block with a stock 6.4" rod. Speculation from some is the shape helps soften the expansion enhances detonation resistance.
    Perhaps naively, the most obvious feature of the engine exterior, the intake manifold, looks just like what we would call the pre-Series I 3800, the LN3. What we call the Series I and II are all Tuned Port style with the long curved, bag of snakes, runners, with the Series II being a lower deck where almost nothing interchanges with earlier models. I am sure what is under that intake manifold is likely different than what I would expect. If there is gallery with photos of the engine interior parts that would be helpful.
     
  2. immortality

    immortality Moderator Staff Member

    Messages:
    13,061
    Likes Received:
    1,501
    Trophy Points:
    113
    Joined:
    Apr 15, 2006
    Location:
    Sth Auck, NZ
    Members Ride:
    HSV VS Senator, VX s2 Calais S/C
    Welcome to the forum.

    What you refer to as the series II (with the lower deck height) is what we call the Ecotec. I believe our Ecotec long block is identical to your engine with the only major difference been the intake manifold and accessories on the front of the engine. The piston listing you mention above will be to suit the ecotec/series II 3800 V6.
     
  3. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    Thank you for the reply. I must admit I am way over my head trying to sort out the various models and sub-types you use vs what I am used to. If I am understanding correctly, that piston is used in the short deck, about 8.5", block? If that is the case, the rod must be much shorter than mine? That is interesting. Many arguments go on here about short vs long rod engines. Is there a proper name for the tall deck, pre-Ecotec engine? Can you tell me if that piston is for a S/C or n/a engine? I have a couple of engines, and this one will be the third, with different compression ratios that I lightly turbocharge, 5-10psi, hence my interest. This piston in my engine would yield about 8.65:1 or 8.85:1 if I cut the deck to close up the piston to head distance.
     
  4. immortality

    immortality Moderator Staff Member

    Messages:
    13,061
    Likes Received:
    1,501
    Trophy Points:
    113
    Joined:
    Apr 15, 2006
    Location:
    Sth Auck, NZ
    Members Ride:
    HSV VS Senator, VX s2 Calais S/C
    Our earlier V6 engines were just referred to as the 3800 V6 but to break it down a bit more the VN Commodore (the first with the V6 engines), which was our series 1 V6 would be what you call LN3 and the later series 2 engine (Late VN to VR Commodore) would be the L27 but with our own intake on it.

    For years I was interested in finding one of your L27 intakes with the alloy tuned upper but no one seemed to be able to help :( My aim was to converter my engine to a forward facing throttle body by flipping the whole intake 180°. Didn't really want one with a plastic upper as a nitrous backfire would probably blow up the whole thing.
     
    monstar likes this.
  5. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    Ahh, it's becoming clearer. I appreciate your patience. What we call the L27 came out in 1990 in only the Buick Regal here. It is still the tall deck engine and only the first year had the aluminum tpi manifold. GM did not use EGR on the aluminum manifold, but I did add it to the one I use on one of my engines since my stock engine was programmed for it. They did add EGR later on the plastic manifolds but with a different operating system. This is a poor pic of the L27 manifold I have with the EGR added on the right side. I might be able to help you with one of those if you are still interested, although winter here is pretty brutal right now. It's supposed to stay above 0*F tonight for the first time since Christmas.
    DSC01077.JPG
     
  6. immortality

    immortality Moderator Staff Member

    Messages:
    13,061
    Likes Received:
    1,501
    Trophy Points:
    113
    Joined:
    Apr 15, 2006
    Location:
    Sth Auck, NZ
    Members Ride:
    HSV VS Senator, VX s2 Calais S/C
    Yep that be the bugger. Our V6 engines didn't get EGR until 1997/98.....

    I follow a couple of Youtubers from PA in the US and the weather looks abysmal there....
     
  7. gtrboyy

    gtrboyy Well-Known Member

    Messages:
    1,051
    Likes Received:
    201
    Trophy Points:
    63
    Joined:
    Jan 25, 2006
    Members Ride:
    vt ss & lc gtr
    Our buicks would look cool with front facing throttle body & relocated alternator.

    Seen a pic TUFFVQ did years ago that turned out really well.

    Most of the quicker buicks here are stocker bottom ends with turbocharger...serious guys end up getting custom forged pistons made or cheaper chev piston(?) with different conrods like Scotty Taylor did on v6vengence.

    Most kits stopped being made or sold like stroker kits for buicks...the little stuff that is left basically for later ecotech engines.
     
  8. immortality

    immortality Moderator Staff Member

    Messages:
    13,061
    Likes Received:
    1,501
    Trophy Points:
    113
    Joined:
    Apr 15, 2006
    Location:
    Sth Auck, NZ
    Members Ride:
    HSV VS Senator, VX s2 Calais S/C
    .... Or use the stock bottom end as it is perfect for boost with the factory 8.5:1 CR and can easily handle 15psi+, the secret is in getting the tune right.
     
  9. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    I'm sure I am not telling you anything new but how about cutting the top off and turning it around? This is a similar manifold to yours, and while not reversed, I added a larger plenum. DSC00030.JPG DSC00842.JPG
     
  10. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    I am still interested where that piston with the raised center is used? The theories here range from clearance for the end of the rod, compression ratio modification or to enhance detonation resistance. The detonation theory posits that the pressure rise is more gradual due to the uneven bowl surface while still providing high average pressure. In my case I am thinking of using it in one of my turbocharged engines.

    Related to the piston question: has anyone used the piston from the circa 2000 Ford 3.8 for high compression to use with E85? In my tall deck 3800, it will yield approx. 12:1.
     
  11. immortality

    immortality Moderator Staff Member

    Messages:
    13,061
    Likes Received:
    1,501
    Trophy Points:
    113
    Joined:
    Apr 15, 2006
    Location:
    Sth Auck, NZ
    Members Ride:
    HSV VS Senator, VX s2 Calais S/C
    I'm not familiar with the piston you talk about unfortunately.

    Yeah I could have just turned mine around and then had to fabricate a whole new neck but it's better to be different. Also, I think your tuned length one performs better than what we have.
     
  12. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    I have not flow tested one of the plastic ones but the aluminum version in my photo flows a bit less than the stock style, what I call a short ram style. My records indicate 204 cfm for the standard style and 182 cfm for the aluminum TPI. This is flow average per port at 28"wc. It seems to work well with my mild turbo setup of only 4 psi.
     
  13. losh1971

    losh1971 Well-Known Member

    Messages:
    3,882
    Likes Received:
    796
    Trophy Points:
    113
    Joined:
    Jan 17, 2010
    Location:
    North Tas
    Members Ride:
    VR Ute V6
    Are you wanting to use keith black silvolites they are a very good pistons
     
  14. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    They are what I generally use for normal rebuilds.
     
    losh1971 likes this.
  15. delcowizzid

    delcowizzid on holiday

    Messages:
    6,658
    Likes Received:
    234
    Trophy Points:
    63
    Joined:
    Jul 8, 2008
    Location:
    NZ
    Members Ride:
    в∞ѕтεכ √&
    The factory pistons in the ln3s take a great deal of boost we are at 23psi no issues over 350kw at the tyres
     
    immortality likes this.
  16. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    Thank you. That's pretty stout and I can only dream of that. My fwd transaxle would likely scatter in many pieces and I was told a couple decades ago the LN3 would spit the crank out at about 500 crank hp. I truly appreciate all the insight. In this case, this was a very low mile engine, 5500mi, that was stored poorly. Water got in through the missing pcv opening and built up in a couple cylinders where the intake valves were open. The crankcase, valley and heads are clean as can be, but the intake ports, intake valves and a couple cylinders rusted. #1 cylinder in particular has a fairly large spot on the minor thrust side that I am in the process of determining if it can be saved. Since it will need new pistons for sure, I was revisiting my options, when I found the Holden piston. The unique bowl shape caused me to question what the purpose is? The compression ratio is sort of middle of the road, 8.6:1, if the bowl volume I received from Silvolite is accurate, 34.7cc., or about 8.82:1 if I have the deck cut a bit to close up the squish distance to the head to about .035". If I understood your nomenclature, this piston is for what you call an Ecotec, similar to our short 8.5" deck Buick 3800 Series II, but quite apparently, not the same.
     
  17. 2seater

    2seater New Member

    Messages:
    9
    Likes Received:
    1
    Trophy Points:
    3
    Joined:
    Jan 7, 2018
    Location:
    Wisconsin USA
    Members Ride:
    None yet
    This is a photo of the piston I received from Silvolite. Does it look familiar? My best guess is it is for a supercharged application. What has baffled me has been the dimensions are correct for an earlier engine used here in the U.S. I did notice when reviewing the specs again that the U.S. Series II engine uses a smaller diameter pin but only the N/A version. The supercharged does use the larger diameter pin to match the earlier engines but the compression height is quite a bit lower to match the low deck. I must admit I am confused by the very limited information I can find but I do like the look of this piston.
     

    Attached Files:

  18. delcowizzid

    delcowizzid on holiday

    Messages:
    6,658
    Likes Received:
    234
    Trophy Points:
    63
    Joined:
    Jul 8, 2008
    Location:
    NZ
    Members Ride:
    в∞ѕтεכ √&
    Iv'e seen similar in a couple of customers l27s they have built one took less timing than normal and they other was a skid car for burnouts and threw the piston off the end of the rod at rpm lol.are they just hypertectic cast pistons they tend to explode with boost or any sign of detonation.we got 8 years of boost out of stock rods and pistons before we lost oil pressure on one rod and decided to finish the engine off in a skid comp and build a fresh one as it had hundreds of drag passes on it and had lived long enough lol.
     
  19. delcowizzid

    delcowizzid on holiday

    Messages:
    6,658
    Likes Received:
    234
    Trophy Points:
    63
    Joined:
    Jul 8, 2008
    Location:
    NZ
    Members Ride:
    в∞ѕтεכ √&
     
  20. immortality

    immortality Moderator Staff Member

    Messages:
    13,061
    Likes Received:
    1,501
    Trophy Points:
    113
    Joined:
    Apr 15, 2006
    Location:
    Sth Auck, NZ
    Members Ride:
    HSV VS Senator, VX s2 Calais S/C
    That poor little motor got raped till the very end....
     

Share This Page