GM has to make another Big Block

[ChevyTech77]

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

[C/K Man]

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

[C/K Man]

And after all that I forgot to mention what a disaster iron cylinder heads are! Anyway, the 8.1L was a good engine, but you have to keep in mind it is an update on '60's technology, and it has some limitations. I used to really like ther old GMC V-6's, and they were outdated in the early '70's. They, like the BBC's, would get the job done. But, not very efficient.

[ChevyTech77]

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

 

 

I know the theory but again, I've seen side by side HC testing done between over square and square engines and they are no where near far enough apart to cause serious issues. They can be cleaned up with other methods and used quite nicely.

 

I can get as much GM Powertrain information as you'd like but on the street, loaded especially, there isn't a 6.0 VVT/6L90 TOUCHING an 8.1 with an Ally, period. That 8.1/Ally combo will pull circles around the 6.0 VVT/6L90 combo all day long and twice on Sunday.

[C/K Man]

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

 

 

I know the theory but again, I've seen side by side HC testing done between over square and square engines and they are no where near far enough apart to cause serious issues. They can be cleaned up with other methods and used quite nicely.

 

I can get as much GM Powertrain information as you'd like but on the street, loaded especially, there isn't a 6.0 VVT/6L90 TOUCHING an 8.1 with an Ally, period. That 8.1/Ally combo will pull circles around the 6.0 VVT/6L90 combo all day long and twice on Sunday.

 

 

GM did clean up the 8.1L enough to pass regulations, but that came at a cost. Terrible volumetric efficiency and poor fuel economy. It was better than the old TBI 7.4's, the head design of the 8.1L helps.

 

Really ashame GM Powertrain didn't go ahead with the V-10 LS. At 7.5L, it killed the 7.4L Vortec. Better emissions characteristics allowed higher compression ratios and more aggressive valve and ignition timing.

[ChevyTech77]

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

 

 

I know the theory but again, I've seen side by side HC testing done between over square and square engines and they are no where near far enough apart to cause serious issues. They can be cleaned up with other methods and used quite nicely.

 

I can get as much GM Powertrain information as you'd like but on the street, loaded especially, there isn't a 6.0 VVT/6L90 TOUCHING an 8.1 with an Ally, period. That 8.1/Ally combo will pull circles around the 6.0 VVT/6L90 combo all day long and twice on Sunday.

 

 

GM did clean up the 8.1L enough to pass regulations, but that came at a cost. Terrible volumetric efficiency and poor fuel economy. It was better than the old TBI 7.4's, the head design of the 8.1L helps.

 

Really ashame GM Powertrain didn't go ahead with the V-10 LS. At 7.5L, it killed the 7.4L Vortec. Better emissions characteristics allowed higher compression ratios and more aggressive valve and ignition timing.

 

Agreed on the 10 cyl LS engine but I think the huge spike in LD Diesel sales put that engine on the shelf.

[yukon25008.1]

I dont completly undertand all of it..but i get what your trying to explain,

I just dont see why with todays technology thy cant make a 400 hp 600 tq big block, thats effecient like the smaller newer motors..is it because they dont want to put the time into it?

I can understand it from the business point, they just want to stamp them out quick and easy to make money,

If a porsche for instance can make 500 hp with like a 3.0 why cant gm take some time and engineering and make big hp and tq effeciently with a new big block?

Also is it not possible to make a new big block with the engine design that only uses 4 cyl,s until you get into it or the demand is required..This way you have a great effecient mpg getter while cruising..and when you have to pull/tow its there.

 

If there was a new/newer big block offered i would own a new body stlye GMC, and they have to know that..that theres a ton of us out here want more than the 6.0 but dont want a d-max.

It would be great if you could get and HD with a 7.0 that made good TQ..someone said the 7.0 is vettes only??

Dont you guys think they would sell great if there was a new improved 8.1 or even 7.4,escpecially if gm garunteed better mpg,s than previous. They also should realize alot of guys dont care what the gas mileage is when buying a truck to do what they want..I pull/haul alot of crap..campers,firewood,work stuff,stone,etc...but dont need a diesel but want more than a 6.0 for sure. Thanks guys for listening..; )

[Daryl Z71]

I dont completly undertand all of it..but i get what your trying to explain,

I just dont see why with todays technology thy cant make a 400 hp 600 tq big block, thats effecient like the smaller newer motors..is it because they dont want to put the time into it?

I can understand it from the business point, they just want to stamp them out quick and easy to make money,

If a porsche for instance can make 500 hp with like a 3.0 why cant gm take some time and engineering and make big hp and tq effeciently with a new big block?

Also is it not possible to make a new big block with the engine design that only uses 4 cyl,s until you get into it or the demand is required..This way you have a great effecient mpg getter while cruising..and when you have to pull/tow its there.

 

If there was a new/newer big block offered i would own a new body stlye GMC, and they have to know that..that theres a ton of us out here want more than the 6.0 but dont want a d-max.

It would be great if you could get and HD with a 7.0 that made good TQ..someone said the 7.0 is vettes only??

Dont you guys think they would sell great if there was a new improved 8.1 or even 7.4,escpecially if gm garunteed better mpg,s than previous. They also should realize alot of guys dont care what the gas mileage is when buying a truck to do what they want..I pull/haul alot of crap..campers,firewood,work stuff,stone,etc...but dont need a diesel but want more than a 6.0 for sure. Thanks guys for listening..; )

 

 

 

This^

[fajitas21]

To be honest with you, there are really not many who want larger than a 6.2L engine, that's why they aren't making them. GM spends a sizable amount of money on market trending to see where people will put their wallets...and while there's a bunch of us on HERE that agree with you, we aren't even 1% of all GM owners unfortunately.

 

Also, with CAFE coming up, GM isn't really able to listen to us, because if they don't make a truck that gets 25 MPGs in a few years, they have to stop selling it...

 

At this point, I completely believe you might be able to get a high-ranking GM guy to side with us on a 7.0L engine or something and STILL nothing would come of it, because at this point the CAFE regs are putting so much pressure on the auto industry to improve MPGs that a core staple of GM's business...truck sales...is in jeopardy.

 

Until the bleeding is stopped...expect AFM / lower gear ratios / Hybrids / better aerodymanics / Transmission efficiency improvements / Weight reductions to take precedence over any power gains.

 

One side note will likely be the introduction of Direct Injection, but that's typically a power gain AND MPG gain...and that's how GM will market it (as they should).

 

If a porsche for instance can make 500 hp with like a 3.0 why cant gm take some time and engineering and make big hp and tq effeciently with a new big block?

 

High HP and High Torque are quite different. Also, I don't want to pay $15000.00 for a premium engine option

[yukon25008.1]

What is direct injection actually?

Just aking because im not sure. If every cylinder now has its own plug,injector,and coil..What could be more direct then that?

[ChevyTech77]

What is direct injection actually?

Just aking because im not sure. If every cylinder now has its own plug,injector,and coil..What could be more direct then that?

 

 

http://en.wikipedia.org/wiki/Gasoline_direct_injection

[spitfire]

Here's a story I came across today: http://www.insideline.com/chevrolet/gm-speaks-directly-about-next-gen-small-block.html

[yukon25008.1]

Why cant they make a version of the corvette 7.0L for the HD trucks

[C/K Man]

Why cant they make a version of the corvette 7.0L for the HD trucks

 

 

I don't know the official reason, but I would imagine the siamesed cylinder walls might be part of it. If GM was going to make a larger displacement LS, my guess is they would use a longer stroke crank in a tall deck (LSX style) block. They could go to 6.6L with the same bore as the current 6.0L.. Hard to say what's coming right now since even the HD pickups will be subject to fuel economy standards. Also, GM was always against using aluminum blocks in HD pickups, but now that policy appears to be changing, as by most reports all the gasoline powered K2XX's (Gen. 5's) will feature aluminum blocks. In other news, there is considerable work being done right now to the old Big Block Chevy for use in medium duty trucks, as a CNG/LNG engine. Origin Engines and Power Solutions International are both working on CNG BBC's for highway use, some are up to 10.4L!

[bagger97]

The big block is dead, unless someone figures out a way to make gasoline from water How many semis are rolling with a gas motor? I could see a big block CNG motor to replace diesel, but not anytime soon.

 

 

They are still using Ford V10 and GM 496 cu in big block in large motor home chassis to keep the cost down. Also, the marine industry still offers the 496 GM big block.

 

2011 was the last year for the GM/Allison in motorhomes. Only the Ford V10 is left in gas.