Piston bowl shape?

[2seater]

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.

 

[Immortality]

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.

 

[2seater]

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.

 

[Immortality]

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.

 

[2seater]

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.

 

[Immortality]

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....

 

[gtrboyy]

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.

 

[Immortality]

.... 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.

 

[2seater]

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.

 

[2seater]

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.