Next gen 8100 V8

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Thread: Next gen 8100 V8

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    Next gen 8100 V8

    The Mark IV big block V8 started life with multiple issues ... the biggest being it's like having four different V-twins stuck together. The 8100 made several improvements, but the most important was ignored. It still has a combustion chamber meant for a 4.47" bore slapped onto a 4.25" bore. The valves were tiny for its displacement. Now in 2019, there is technology to make a cohesive new engine, aimed at maximizing BSFC, lowering friction, and pumping losses. You can also find some efficiencies in leveraging the Gen V small block tech and parts. If you're going to reintroduce a big block, DO IT RIGHT. It could be your last chance!

    I'd use a 111 mm bore and 105 mm stroke. This makes the best use of the bore spacing while still allowing cooling between cylinders. The shorter stroke simultaneously lowers the piston speed and attendant friction, and the longer rod also reduces friction. Since torque is proportional to displacement and volumetric efficiency, NOT stroke, this engine would make much more torque at the same rpm as the 8100, and with lower pumping losses it would get almost 20% better fuel economy.

    A 8.1L needs 58.4mm intake valves to lower pumping loss, and a fairly large exhaust valve (46mm) to maximize torque at part throttle. Big ports don't hurt torque. 360 cfm intake and 270 cfm exhaust may sound high, but it's what a 496 needs. Raised ports and short cam duration will boost torque and response. Short ram intake also reduces pumping loss, reduces cross-talk (similar to a dual plane intake), and boosts low rpm torque by 15%. Like the Ford 7.3L V8, use port fuel injection with Denso UC injectors; it's cheap, quiet, and resist carbon build up. If you do stick with GDI in order to leverage the current EMU, go to 350bar.

    The basic Gen V combustion system is pretty good, but the port between the pushrods was the "bad" port on the Mark IV. The 8100 actually got this right by putting the port outside the pushrod (too bad the port itself was horrible). Ideally you would use the NASCAR R07 valve layout. It optimizes in-cylinder mixture motion with ports between the pushrods, while being more compact than the Mark IV.

    The 8100 should be brought into the small block fold and benefit from its technologies. Stretching a gen V V8 will make the 8100 only 2" longer. A cast iron block and aluminum heads would be marginally heavier than the 6.6L. Share LTX parts, like water and oil pumps, VVT, flex plate, 8 and 10 speed transmissions, and dynamic skip fire.

    The sum of all this is a reasonable 425 bhp @ 4600 rpm, minimum of 525 lb-ft @ 3500 rpm, with at least 400 lb-ft just off idle, and approaching 20 mpg highway. The eventual crate engines will out power the ZZ572, on pump gas. It can also be bored and stroked beyond 9.0L.

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    Re: Next gen 8100 V8

    Interesting idea. I question whether the business case will support developing an entire new block casting, which reintroducing the BBC would be (unless is GM still casting BBC's for the aftermarket business?). I suppose this will depend on if the larger displacement gas engines such as the new 6.6 and Ford 7.3 really catch on and diesels start to fall by the wayside.

    I think 20mpg highway is probably really asking a lot for a large bore V8. And we know gassers suffer badly when towing.

    But to go with a bigger displacement V8 they'd have to cast a new block, the LS/LT architecture isn't going to go much bigger than 6.6 at the expense of durability.
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    Re: Next gen 8100 V8

    wonder dimensionally how the "PSI" 8.8L engine is
    it is derived from the BBC

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    Re: Next gen 8100 V8

    Interesting. There are rumors that a new gasoline engine may be under development, something larger than 8L destined for future Navistar/GM joint venture trucks. There is no hard information on the program yet, and some speculation that PSI may be involved in its development.

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    Re: Next gen 8100 V8

    Quote Originally Posted by richmond2000 View Post
    wonder dimensionally how the "PSI" 8.8L engine is
    it is derived from the BBC
    That's a neat engine. Looks like a mildly reworked 8100. It has a 4.35" bore, but still has many of the same issues of regular BBC.

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    Re: Next gen 8100 V8

    Quote Originally Posted by NHRATA01 View Post
    Interesting idea. I question whether the business case will support developing an entire new block casting, which reintroducing the BBC would be (unless is GM still casting BBC's for the aftermarket business?). I suppose this will depend on if the larger displacement gas engines such as the new 6.6 and Ford 7.3 really catch on and diesels start to fall by the wayside.

    I think 20mpg highway is probably really asking a lot for a large bore V8. And we know gassers suffer badly when towing.

    But to go with a bigger displacement V8 they'd have to cast a new block, the LS/LT architecture isn't going to go much bigger than 6.6 at the expense of durability.
    I started a thread several years back about an all aluminum 4.5L V6 based on the gen IV architecture, and they gave us the 4.3. I just want them to do a proper, state-of-the-art V8 instead of just rehashing the BBC, again. I think a lot of people would be very happy with a scaled up LV3 (not many people know that the V6 was the focus of GM's 10 million hours of simulation work and just modified for the 5.3 and 6.2).

    You're right about mpg under towing going to heck. That's why I emphasized optimized operation under part throttle. Low pumping loss and low friction are key. I agree that 6.6L is a realistic size limit to an OE truck engine. The Ford 7.3L looks to be a small block with ~4.5" bore centers.

    Ford did a clean sheet engine, why can't GM? Ford figures 7.3L is ideal for the HD market. tbh, 7.4L might be a more practical displacement. 496 (cid) is a perfect/ideal number. In fact, 8128 (cc) is the next perfect number in the sequence. Doubly perfect. Just a little math geek for you

    As displacement grows, it gets much harder to use large enough valves. The 8.1 has to be quite oversquare to accommodate large enough valves. If you scale up a 4.3L, you get 58 mm intake and 46 mm exhaust valves (scaling up the 5.3L gives 60 mm intake valve). Bigger exhaust valve gives you much better low end torque and part throttle operation. It needs a 4.47" bore to comfortably fit those valves for a mass produced, low cost engine.
    Thus stroke becomes 3.95".

    The 4.47" bore should be the largest bore with non-siamesed block. BBC can obviously go up to 4.60" bore. Pro stock uses 4.70" bores and are the quickest accelerating cars on the planet ... so big bore is not an issue with the right combustion system. If fuel is injected directly into the center of the bore, the air swirling around the cylinder acts as insulation, which reduces heat lost to the cooling system. The house-sized engines on ships get over 50% brake thermal efficiency. With 11:1 compression, the larger the bore, the flatter the combustion chamber, which also reduces heat loss.

    The pro to the short stroke is that the crankshaft gets lighter, rods get much shorter, which allows the "short" deck (9.8") and the engine becomes much lighter (the con is slightly lower BSFC). The 8100 is 750 lb, and with aluminum heads this hypothetical engine would be around 620 lb.

    The 4.3L produces 11.18 bar BMEP at 16.25 m/s piston speed. If the 8.1 had 15 mm lift with the same 193 degree cam, (I think that's possible with a 60 mm cam and a hollow intake valve at such low rpm) it would produce 490 bhp @ 4800 rpm, and 575 lb-ft on gasoline. E85 gives 4.5% more power and bumps that up to 515 bhp and 602 lb-ft. That's what the math says. GM would probably limit it to 14mm lift so they can use their standard valve spring. With cam/heads/headers we'd be looking at well over 700 bhp...from a "truck" engine. It would be a great crate engine, or salvage swap down the line.

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    Re: Next gen 8100 V8

    Quote Originally Posted by ogg vorbis View Post
    I started a thread several years back about an all aluminum 4.5L V6 based on the gen IV architecture, and they gave us the 4.3. I just want them to do a proper, state-of-the-art V8 instead of just rehashing the BBC, again. I think a lot of people would be very happy with a scaled up LV3 (not many people know that the V6 was the focus of GM's 10 million hours of simulation work and just modified for the 5.3 and 6.2).

    You're right about mpg under towing going to heck. That's why I emphasized optimized operation under part throttle. Low pumping loss and low friction are key. I agree that 6.6L is a realistic size limit to an OE truck engine. The Ford 7.3L looks to be a small block with ~4.5" bore centers.

    Ford did a clean sheet engine, why can't GM? Ford figures 7.3L is ideal for the HD market. tbh, 7.4L might be a more practical displacement. 496 (cid) is a perfect/ideal number. In fact, 8128 (cc) is the next perfect number in the sequence. Doubly perfect. Just a little math geek for you

    As displacement grows, it gets much harder to use large enough valves. The 8.1 has to be quite oversquare to accommodate large enough valves. If you scale up a 4.3L, you get 58 mm intake and 46 mm exhaust valves (scaling up the 5.3L gives 60 mm intake valve). Bigger exhaust valve gives you much better low end torque and part throttle operation. It needs a 4.47" bore to comfortably fit those valves for a mass produced, low cost engine.
    Thus stroke becomes 3.95".

    The 4.47" bore should be the largest bore with non-siamesed block. BBC can obviously go up to 4.60" bore. Pro stock uses 4.70" bores and are the quickest accelerating cars on the planet ... so big bore is not an issue with the right combustion system. If fuel is injected directly into the center of the bore, the air swirling around the cylinder acts as insulation, which reduces heat lost to the cooling system. The house-sized engines on ships get over 50% brake thermal efficiency. With 11:1 compression, the larger the bore, the flatter the combustion chamber, which also reduces heat loss.

    The pro to the short stroke is that the crankshaft gets lighter, rods get much shorter, which allows the "short" deck (9.8") and the engine becomes much lighter (the con is slightly lower BSFC). The 8100 is 750 lb, and with aluminum heads this hypothetical engine would be around 620 lb.

    The 4.3L produces 11.18 bar BMEP at 16.25 m/s piston speed. If the 8.1 had 15 mm lift with the same 193 degree cam, (I think that's possible with a 60 mm cam and a hollow intake valve at such low rpm) it would produce 490 bhp @ 4800 rpm, and 575 lb-ft on gasoline. E85 gives 4.5% more power and bumps that up to 515 bhp and 602 lb-ft. That's what the math says. GM would probably limit it to 14mm lift so they can use their standard valve spring. With cam/heads/headers we'd be looking at well over 700 bhp...from a "truck" engine. It would be a great crate engine, or salvage swap down the line.
    Great Ideas and would work.

    What do you think of a RB LS/LT?

    Thinking of ~4.125 Bore and Stroke lengthened to create a 7.0L to 7.4L.

    Would be lower cost to develop than "All New" and could still use LS/LT heads (with valve sizes adjusted for displacement).

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    Re: Next gen 8100 V8

    Speaking of the Ford 7.3L, I was surprised it didn't have greater bore centers.

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    Re: Next gen 8100 V8

    Quote Originally Posted by SierraGS View Post
    Great Ideas and would work.

    What do you think of a RB LS/LT?

    Thinking of ~4.125 Bore and Stroke lengthened to create a 7.0L to 7.4L.

    Would be lower cost to develop than "All New" and could still use LS/LT heads (with valve sizes adjusted for displacement).
    There are may reasons that would be a smart move. It would be reasonably cheap to do, compact and light (530 lb), and be plug and play with any LT. You need cooling between cylinders for CNG, so bore has to stay at 4.065". A 9.75" tall deck would comfortably fit 4.125" stroke, for 7.0L (requires a new intake manifold). The heads, imho, are sports car heads and have relatively small exhaust valves. They make good numbers at WOT, and will give up lots of low rpm torque and at part throttle - which will impact real world fuel economy. The 6.6 makes 10.5 bar @ 17 m/s piston speed. A 7L would make 400 bhp @ 4900 rpm and 490 lb*ft with the same cam.

    If they went siamesed bore, they can get 454 cid. Would they just use the LT1 head, or a specialized head? LT1 heads would still make 400 hp @ 4600 and 525 lb*ft. Scaling up the LV3 calls for a 56mm intake valve and 44.45mm exhaust and would give 430 bhp @ 4900 rpm, and 525 lb*ft, with much better part throttle torque. Ford's 7.3 makes 400 lb*ft @ 1500 rpm ... I'd expect more from the 454.

    I understand a specialized engine with only 10% more torque seems frivolous ... but darn it, I want them to fix the BBC. There are plenty of applications that call for an 8.1. Realistically, they will do the bare minimum to have "class leading" performance. GM has said they "could" do a big block, so let's see what they deliver.

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    Re: Next gen 8100 V8

    A reborn Big Block would be something that could be marketed to other OEM's. Look how many commercial vehicles from other OEM's are running around with L96's in them. Not to mention Navistar.

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    Re: Next gen 8100 V8

    Quote Originally Posted by Sierra12 View Post
    A reborn Big Block would be something that could be marketed to other OEM's. Look how many commercial vehicles from other OEM's are running around with L96's in them. Not to mention Navistar.
    Navistar and Workhorse BOTH would use it assuming workhorse does NOT stop building chassis with "ICE" engines in there dream of electrics and helicopters

    the new 7.3L will be interesting once it starts replacing the V10 in 3RD party applications
    the PSI8.8L is said to offer the same performance as a CUMMINS 6.7 "ISB" in school bus applications and THAT IS A BIG market for petrol/GAS engines over Diesel
    with emissions systems and "derates" and downtime

    and the LION ELECTRIC is TOO expensive to buy / deploy in real numbers

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    Re: Next gen 8100 V8

    Quote Originally Posted by ogg vorbis View Post
    There are may reasons that would be a smart move. It would be reasonably cheap to do, compact and light (530 lb), and be plug and play with any LT. You need cooling between cylinders for CNG, so bore has to stay at 4.065". A 9.75" tall deck would comfortably fit 4.125" stroke, for 7.0L (requires a new intake manifold). The heads, imho, are sports car heads and have relatively small exhaust valves. They make good numbers at WOT, and will give up lots of low rpm torque and at part throttle - which will impact real world fuel economy. The 6.6 makes 10.5 bar @ 17 m/s piston speed. A 7L would make 400 bhp @ 4900 rpm and 490 lb*ft with the same cam.

    If they went siamesed bore, they can get 454 cid. Would they just use the LT1 head, or a specialized head? LT1 heads would still make 400 hp @ 4600 and 525 lb*ft. Scaling up the LV3 calls for a 56mm intake valve and 44.45mm exhaust and would give 430 bhp @ 4900 rpm, and 525 lb*ft, with much better part throttle torque. Ford's 7.3 makes 400 lb*ft @ 1500 rpm ... I'd expect more from the 454.

    I understand a specialized engine with only 10% more torque seems frivolous ... but darn it, I want them to fix the BBC. There are plenty of applications that call for an 8.1. Realistically, they will do the bare minimum to have "class leading" performance. GM has said they "could" do a big block, so let's see what they deliver.
    Thanks, lot more great information.

    I can see GM doing a 7.0L using the 4.065 Bore and 4.125 Forged Crank from the existing LSX (should be strong enough) and updating the heads similar to your guidelines. It would be a quick to market and cost effective way to become more competitive and should be able to produce power numbers ~ equal to Ford's new 7.3L. GM might be able to go up to a 4.25 Stroke for a 7.2L but not sure it would be worth the investment in a new crank. I think that the bore size max of 4.065 limits the SB to 2500/3500/4500 usage but that is a very large market and the 7.0L or 7.2L would be power and MPG competitive with Ford's 7.3L.

    The best part of creating the 7.0L from "available parts" is the low cost of development. Yes, there would need to be a new block but it can probably be machined on existing tooling with minimal modifications and it should get heads with valve sizes adjusted for "Truck" use and would probably need new pistons for long term durability.

    Creating a viable 7.0L or 7.2L for HD Pickups/Vans that could be used in 1500 Truck, SUV and Vans along with Crate Engines frees up GM to create a 7.4L to 8.1L "Big Block" (or larger) engine family that could be used in Max Tow 2500/3500/4500 and of course 5500 and up Medium Duty Truck/Van/Bus markets. The larger displacement can be efficient as you point out if it is properly designed from the beginning as a "Truck" engine and it's larger displacement would mean it is not as stressed while delivering great real world performance. And as you point out, it can easily be modified with for street performance/crate engine use and fit most applications.

    And as Sierra12 points out GM could market this to many other Medium Duty Truck makers and even to Farm and Construction Equipment makers.

    GM can do both.

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    Re: Next gen 8100 V8

    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.

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    Re: Next gen 8100 V8

    A 4.125 stroke on an LS/LT is really pushing the limits of the block design. At stock deck height the sleeves are bordlerline too short. Guys building race setups will either use a special piston and/or a resleeved block, but they more often than not end to have oil consumption issues due to the compromised piston design for a higher wristpin to allow for the longer stroke, as well as increased sidewall loading leading to quicker wear. I have a 454 cube LS in my TA which is 4.185x4.125, but its a car that sees 1k miles per year and I would never expect to get 100,000 miles out of it. We're talking commercial use as a diesel alternative, fleets are going to want an easy 200-300K and certainly without excessive oil consumption. I don't see a 4.125 LS being able to do that. Keep in mind even the new 6.6 is <4.0" stroke.
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    Re: Next gen 8100 V8

    That's true, and that leads to the question of a tall deck LS/LT.

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