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Thread: Next gen 8100 V8

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    Quote Originally Posted by Sierra12 View Post
    That's true, and that leads to the question of a tall deck LS/LT.
    now that’s another option if say the deck height is raised to 10” or 10.2” like the old truck blocks. You might be able to swing a 4.25” or 4.5” crank in something like that and set the rpms lower than 5,000 rpm for added durability.

    I’d be looking at higher lift out of the cam and valves, at lower rpms, a longer valve and springs can be used to make it reliable at that rpm range, a bit like what the Ford 7.3 is doing.
    Last edited by jpd80; 10-08-2019 at 04:21 PM.

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    Re: Next gen 8100 V8

    Quote Originally Posted by ogg vorbis View Post
    I'm more lucid when I'm NOT posting at 5am I did some more math.

    I'm not a fan of just throwing LT1 heads on a larger engine and calling it a day. The intake pumping losses are OK for the 7L, but the exhaust pumping loss goes through the roof. I can tell the Ford 7.3 uses similar size valves because the torque curve is a mountain instead of a flat line.

    A 7L calls for 2.126" x 1.71" valves. That might not fit in a 4.065" bore, and a 4.125" is not great in a standard deck block. Not a good engine.

    A 7.4L calls for 2.19" x 1.77" valves. 430 bhp @ 4900, 525 lb*ft and 415 lb*ft @ 1500 (although I'd gladly give up 25 peak torque for 20+ low end torque). Another route is a small block with 4.6" bore centers and 9.5" deck. 4.25" bore x 4.0" stroke. It gains a fraction of an inch in every dimension. The optimal external size and weight for the displacement. The LT can't grow this big, and small bore is a waste for a BBC.
    Any LT based HD engine larger than the 6.6L will have to be a RB (Raised Block) or "Tall Deck" with the 4.065" Bore to maintain the durability and think that 7.2L (4.25" Stroke) would be the realistic Maximum since using a 4.185" B Siamese Block and 4.25 S would not have enough cylinder cooling for HD use. The 7.0L makes the most sense since GM already has the Forged Crank with the 4.125" Stroke that should be strong enough for HD usage and deliver power numbers similar enough to Ford's 7.3L to be competitive.

    Think a new "Big Block" would have a Bore/Stroke Similar to Ford's 7.3L 4.22" B x 3.976" S and think the LSX 7.4L 4.25" B x 4.00" S would be the one used for 2500/3500/4500 and go to 4.25" B x 4.37"S for 8.1L Engines that would be more for Commercial use. The larger Bore provides enough room for the valves without creating too much added Bore friction.

    Think it will matter how much GM is willing to spend on a HD engine larger than the 6.6L and don't think they would use the old 8.1L Block to base it on, but could be an option. Not sure how "Modern" (Size/Weight/Strength) the old 8.1L Block is in relation the Ford's 7.3L. If GM could use Modern casting techniques on the block and add "LT" Heads modified for "HD Truck" use then it would be a viable option.

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    Re: Next gen 8100 V8

    I had heard that the 8.1L could have easily gone much larger but GM wanted to use a cast iron crankshaft which limited stroke to 4.37". When PSI took the 8.1L over, they installed a forged crank and went to 8.8L with a 4.5" strole and slight bore increase.

    Very interested in the rumors that GM is working on a large truck V-8 over 8L.

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    Re: Next gen 8100 V8

    Quote Originally Posted by Sierra12 View Post
    I had heard that the 8.1L could have easily gone much larger but GM wanted to use a cast iron crankshaft which limited stroke to 4.37". When PSI took the 8.1L over, they installed a forged crank and went to 8.8L with a 4.5" strole and slight bore increase.

    Very interested in the rumors that GM is working on a large truck V-8 over 8L.
    Certainly doable...not sure if GMPP still sells it but they at one point offered a 572cid BBC.
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    Re: Next gen 8100 V8

    I've been looking at pro stock DRCE heads lately. They are state-of-the-art as far as naturally aspirated OHV V8. I really like the four long head bolts which really helps clamp the head better than the LS short bolts. Then I stumbled upon Dart's 10* LS race head which looks like a smaller DRCE head. Both valves are canted, oval ports. They've already made 1160 hp from 400 cid and rev to 10k. The heads alone sell for $6k; a complete engine is $65k. Imagine an entire crate engine that sells for about $6k ... or junkyard engine for a grand.

    A high nickel cast iron block would be nice, but an aluminum version can be made to handle 2500hp and shed 80lb (which saves a lot of money with logistics). With a 6.13" cam height and 9.5" deck height it would still have 1/2" shorter pushrods than the LS (GM engineers admitted the LS7 valvetrain is stable to 8200 rpm). A 60mm cam with even better geometry should be happy at 9k+ rpm.

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    Re: Next gen 8100 V8

    Man I remember the days when everyone used to get excited when a new pushrod V8 surfaced and the rumors of tons of cool cars would soon follow. Now it's theory after theory of what power it should make in the next bread truck. Such a bummer.

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    Re: Next gen 8100 V8

    This isn't the rumours section. This is *my* letter to GM.

    Here are a few of my reasons:
    *ICE are not dead, but they're going away, so GM's window of opportunity for producing a killer V8 is shrinking.
    *Ford made a killer V8 and it's eating GM's lunch right now.
    *GM needs a bigger V8 for HD trucks and SUV anyway. Why not make it the best it can be?
    *The 8100 already had canted valve heads - and they were some of the crappiest heads GM has ever produced.
    *LTX are quite good for a mass-produced engine, and not state-of-the-art.
    *I want to democretize a state-of-the-art OHV V8.
    *It would have class leading power, emissions, reliability, and fuel economy. port fuel injection and naturally aspirated are the cheapest to maintain and repair. GDI performance degrades quickly and requires further maintenance.

    My plan would also be a nod to the C4 LT5 which is still impressive by today's standards. It was supposed to have 4.55" bore centres until GM forced Lotus to stay with 4.4". It had a 14.5:1 compression with flat top pistons - it used dished pistons to bring it down to 11:1. Giving the new 4.60" small block 70mm main bearings would provide a supply for LT5. The new C8 DOHC 5.5L also shares the LT5's 93mm stroke with a 97mm bore. I imagine it also shares its 39mm intake valves.

    Thanks to those that have humoured my fantasy. Let's see what GM comes up with.

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    Re: Next gen 8100 V8

    Quote Originally Posted by ogg vorbis View Post
    Bozi just released a series of videos detailing the 7.3L Ford engine.
    4.22" x 3.976" = 445 cu.in
    9.65" deck
    9.53" bore centers
    rods should be about 6.35" long (1.60:1 rod/stroke)
    60mm diameter cam
    2.17" x 1.67" valves
    320 cfm intake flow - I'm guessing 220-230 cfm exhaust
    8.8 degree valve angle, with ~1.9 degree cant (basically an LT1 head with rolled valve angles)
    0.530" intake valve lift, 0.600" exhaust valve lift
    10.5:1 compression ratio
    port fuel injectors in the heads (like the supercharged 3800)
    430 hp @ 5500 rpm 475 lb-ft @ 4000 rpm
    cast iron block good for over 1800 hp (with a nice valley to collect leaves and sand)
    bare engine weighs 530 lb
    made 563 hp @ 6000 rpm with just cam and headers (no accessories)
    variable displacement oil pump (sump mounted)
    hydraulic variable cam phasing (same as LTX)

    The 6.6 is inadequate. SB2 style heads would be a step change to the inline valve architecture. I LOVE the idea of a 4.60" bore center "LTX" 454 with raised cam, 56 mm x 43 mm valves, oval port, short ram intake and 1-5/8" exhaust manifold. I'd love priority main oiling and sump-mounted oil pump (instant prime). The heads can flow 360 cfm / 265 cfm as cast. With the large cam, I'm sure you could get 193*/199* duration with .571/.551" lift. Realistic 450 hp @ 4800 rpm and 500 lb-ft with a super flat torque curve and 10% better mpg than the 7.3. Easy 600 hp with cam and headers (with full accessories). And it'd only be 20mm longer, and 6mm wider. The only problem is, what do you call something that can crush the king of the monsters?
    Thanks for the info, lot of good data (BTW I think you mean 4.53" Bore Centers for the 7.3L).

    Think you cover the most important design features that a new GM HD Engine should have

    What Bore/Stroke are you proposing?
    These are the Current ones along with the "old 8100" and the PSI 8.8L
    6.6L HD 4.065" x 3.86"
    Ford 7.3L 4.22" x 3.976"
    454 LSX 4.185" x 4.125" (Current GM performance LS Crate Engine)
    '01-'06 8.1L 4.25" x 4.37"
    8.8L PSI 4.35" x 4.50"

    The size/weight difference will not be an issue with HD Trucks since the 6.6L Duramax or the 1500 Truck/SUV and Vans since they are so small ~0.236" Wider and ~0.79" Longer.

    Port Injection is the way to go for HD applications and think GM could easily incorporate production of this engine into an existing LS Engine plant.

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    Re: Next gen 8100 V8

    Quote Originally Posted by ogg vorbis View Post
    I've been looking at pro stock DRCE heads lately. They are state-of-the-art as far as naturally aspirated OHV V8. I really like the four long head bolts which really helps clamp the head better than the LS short bolts. Then I stumbled upon Dart's 10* LS race head which looks like a smaller DRCE head. Both valves are canted, oval ports. They've already made 1160 hp from 400 cid and rev to 10k. The heads alone sell for $6k; a complete engine is $65k. Imagine an entire crate engine that sells for about $6k ... or junkyard engine for a grand.

    A high nickel cast iron block would be nice, but an aluminum version can be made to handle 2500hp and shed 80lb (which saves a lot of money with logistics). With a 6.13" cam height and 9.5" deck height it would still have 1/2" shorter pushrods than the LS (GM engineers admitted the LS7 valvetrain is stable to 8200 rpm). A 60mm cam with even better geometry should be happy at 9k+ rpm.
    Like the longer Bolt idea as well as a High Nickel or maybe a CGI Block that most Fleet operators prefer and should definitely be an Aluminum version for HP and Crate Engines and if the Aluminum Block could be made durable enough (more upfront/production costs) it would be offset with logistical savings. Shorter Pushrods would help as well.

    As you stated previously, the 6.6L will not be enough for more extreme HD applications or Class 4 and up HD and Medium Duty Applications. The 6.6L will be fine for it's better MPG for most 2500 HD uses and those who do not tow heavy loads with 3500 HD's but GM has to offer something larger for those who will be looking for a Gasoline Engine alternative.

    The Gasoline Fleet market is growing and Gasoline Engines are commonly modified for Gas/LPG (Bi-Fuel), LPG (Propane) and CNG (Natural Gas) usage that offer Near Zero Emissions so needing an engine larger than the 6.6L Gas is a given.

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    A 6.6 was never going to cut it in MD, give the iron block a taller 9.7” deck height and increase stroke to 4.25”. More bottom end torque and better engine all around.

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    Re: Next gen 8100 V8

    Quote Originally Posted by ogg vorbis View Post
    This isn't the rumours section. This is *my* letter to GM.

    Here are a few of my reasons:
    *ICE are not dead, but they're going away, so GM's window of opportunity for producing a killer V8 is shrinking.
    *Ford made a killer V8 and it's eating GM's lunch right now.
    *GM needs a bigger V8 for HD trucks and SUV anyway. Why not make it the best it can be?
    *The 8100 already had canted valve heads - and they were some of the crappiest heads GM has ever produced.
    *LTX are quite good for a mass-produced engine, and not state-of-the-art.
    *I want to democretize a state-of-the-art OHV V8.
    *It would have class leading power, emissions, reliability, and fuel economy. port fuel injection and naturally aspirated are the cheapest to maintain and repair. GDI performance degrades quickly and requires further maintenance.

    My plan would also be a nod to the C4 LT5 which is still impressive by today's standards. It was supposed to have 4.55" bore centres until GM forced Lotus to stay with 4.4". It had a 14.5:1 compression with flat top pistons - it used dished pistons to bring it down to 11:1. Giving the new 4.60" small block 70mm main bearings would provide a supply for LT5. The new C8 DOHC 5.5L also shares the LT5's 93mm stroke with a 97mm bore. I imagine it also shares its 39mm intake valves.

    Thanks to those that have humoured my fantasy. Let's see what GM comes up with.
    You are correct about the ICE engine being around for while, especially in HD use where heavy loads carried over long distances are common.

    Another factor is that ICE engines in fleet use can be made very environmentally friendly with LPG and/or CNG conversions and are in use by many commercial fleets today so the fueling infrastructure and logistics are already proven and in place making them an attractive alternative to Turbo Diesel and EV's.

    What do you think about S/C or Turbos?

    Think that a new HD engine has to offer a "Boosted" variant of some kind for better high altitude performance as well a potential for better MPG where a smaller engine could be used or the larger ones under less stress.

    GM could develop a range of HD engines that would start with the current 6.6L in NA and Boosted variants (S/C or Turbocharged) with a 7.4L, 8.1L and possibly larger engines like the 8.8L. A 6.6L S/C variant would be easy to do a utilize GM's experience with the LS S/C engines and a 6.6L Turbo would be even more powerful and that technology could be applied to the smaller 5.3L and 6.2L LS engines. The larger engines would be quite powerful with the 7.4L S/C capable of over 600 HP in HD trim (HD power levels tend to be lower for durability) and the larger engines could produce Torque figures rivaling recent Turbo Diesels. Turbocharged versions would produce even more power and could use a single large Turbo since Turbo Lag is not as important in HD trucks and most Fleets have experience with them.

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