5th Gen Z28, Gen V Engine.

[thePill]

Valve sizes: you don't build a 4.00" bore engine with 2.20"/1.60"+ valves..."shrouding" happens. Take a look at LS1/LS6 engines: smallish bore = smallish valves. Pretty much max'd @ 2.05".

Valve sizes, alone, do NOT correlate to greater revs. In fact, a smaller valve weighs less, and theoretically can be rev'd higher... That's part of the reason that a 4-valve engine revs higher than an equivalent 2-valve.

With a 4 inch bore, you would still have some room for a 3.80 combined valve radius, it would be tight but it could happen. The LS7 has a 4.125 bore and a combined valve radius of 3.81, as that is a tight squeeze, valve angle could help in that situation. Although larger valves do slow down the valvetrain and limit RPM, there is a substantial trade off here. 2 valve engines are limited by their total valve area by design. Large intake valves are a requirement if high RPM's are desired. Limiting the intake valves size will start a chain reaction of events, all of which are parasitic losses and inefficiency. If an OHV engine wants to breathe above 7000rpm. All the high rise intakes and head design in the world will be stopped dead at the choke point (intake valve). We will have to wait to see this "new combustion design" GM is working on to really say what’s going to happen. This also would solidify my squared bore and stroke option. I would like to see a bore and stroke between 3.80 and 3.90 but this would naturally see the valve size decrease unless major angles were used on the valves (I would like to keep them similar to the LS7).

Well, you tried. I really have learned a lot from your thread, it's just that the average enthusiast,(like me), don't have a real understanding of how all of the basic parts of an internal combustion engine work. Some of this stuff is over my head,(for now), but is still a great read. Thanks for sharing. I hope you're just not a really smart Mustang fan trying to throw us all off, cause right now I wouldn't be able to tell the difference.

The Cam in Cam design is new to me, this is why I naturally pick at the people I know and do quick diagram concepts of operation. I won't sneak around and try to throw Camaro guys off... I am usually very direct but I have to be on my best behavior for awhile so I can gain access to the ZL1 section again. I started this thread as a workshop for me. Sometimes you will see me post something and then correct myself in the very next post. I like to leave the mistakes up so I can go back to my original idea if I can't think any further. I can also link this directly to some of my helpers and they can trace my steps. Anyway, thanks for reading...

I agree this is the motor we want in the Z28, but sadly I just don’t see it making it into the Camaro until 2014 and in the new alpha platform.

It depends on where GM is at in development, If the 2012 C7 Corvette is going to be using the Gen V, then it isn't crazy to think that a 2013 Camaro could carry one. I simultaneous release in both the Corvette and the Camaro would tell me that GM is ready to over step the Corvette or at least meet it evenly with their sport coupe entry. This would also let the Camaro fans know that the Camaro is no longer a solid second.

[Blizzard]

Originally Posted by thePill

It depends on where GM is at in development, If the 2012 C7 Corvette is going to be using the Gen V, then it isn't crazy to think that a 2013 Camaro could carry one. I simultaneous release in both the Corvette and the Camaro would tell me that GM is ready to over step the Corvette or at least meet it evenly with their sport coupe entry. This would also let the Camaro fans know that the Camaro is no longer a solid second.

Thats if we get the C7 in 2012, but has there been any hint of this? i dont remember any real concepts.

[brandotron]

Originally Posted by thePill

[FONT=Verdana][COLOR=black]It depends on where GM is at in development, If the 2012 C7 Corvette is going to be using the Gen V, then it isn't crazy to think that a 2013 Camaro could carry one. I simultaneous release in both the Corvette and the Camaro would tell me that GM is ready to over step the Corvette or at least meet it evenly with their sport coupe entry. This would also let the Camaro fans know that the Camaro is no longer a solid second.

And we've seen engine changes mid-generation on the Camaro before. Cool thread. I've been hearing about this forever, but this is the first I've seen of it.

[Blizzard]

Doing some research says we dont see a C7 until 2013 model year so still 2014 model year for Camaro wich most likely means alpha platform to help meet Cafe standards

[LOWDOWN]

Your "theory" here is based on all-out rpm/racing...which ISN'T the stated purpose, day-in and day-out of ANY regular production engine...especially with design features and technology necessary for TRUCKS, the overwhelming volume-required use for this architecture.

Cylinder head tech. will be slanted, generally, to TORQUE as opposed to HP...where velocity is most important. Think "small port" vs. "large port"... Small for trucks and "regular" passenger requirements with low- and mid-range usage (generally), large(r) for performance applications. Emissions and fuel economy will be at least as important as all-out rpm/power. And at lower speeds, TORQUE moves the "load". More torque, less pedal...less emissions...less fuel consumption. And THAT'S where VVT (regardless of methods used) will have its every-day applications.

Performance applications? Time the VVT, and design the cylinder heads, accordingly. With 7- and 8-speed trannies for both emissions and CAFE compliance at part-throttle.

BTW, contact LPE or Katech and request 3.8" worth of valves in your 3.98" bore LS1...ain't gonna happen...

...and all other things being equal, which they never are, an over-square engine (bigger bore than stroke) will out-rev an under square one (stroke bigger than bore) every time. Compare the characteristics of a 302 (Z/28) to a 307 long-stroke... Bore makes rpm, stroke makes torque.

[thePill]

A huge factor here would be the valve sizes, what would be the point of increasing the RPM's of an OHV pushrod engine if the valve sized limited the airflow beyond 7000rpm's. I had a square bore and stroke 5.739 liter (350.17 cubic inch) engine laid out for fun and nostalgia. I went with a 3.81 bore and a 3.84 stroke but that would greatly reduce the size of the valves. The old Chevy 350 had a 4.0 inch bore and a 3.48 inch stroke, it is becoming more obvious that GM will maintain a 4.00 inch bore just to accommodate larger valves. So, for nostalgia’s sake, a Gen V 5.7 liter V8, using the LS7's 4.125 bore (which is likely and would be a good move if you asked me). We could make a 5.7/350 with a 4.125 bore and a 3.27 stroke (5.728 liter/349.53 ci), and could go up to a 3.279 stroke for a maximum 5.744 liter/350.49 liter). That would allow for HUGE valves 2.20i and 1.61e and would be more than enough valve area to allow deep breathing at high RPM. They will probably share the 12 degree valve angle and would help with the valve shrouding. Valve shrouding is usually a problem for OHC's and OHV's that use huge valves. Angling the valves provides more room between the valve and the cylinder wall, angling too much is not good either but most engineers have found a happy medium between cylinder wall shrouding and maintaining a flat valve area.

But... a 5.7 might defeat the whole purpose of having a global block design. GM would typically like to cover a wide range of applications with a global block. I heard before that a 5.3 and a 6.2 would be offered. That would be a very nice range of applications. The 5.3 would be for entry level sports coupes/cars, lightweight trucks and light-medium sedans. The 6.2 would cover the remaining high level sport coupe/cars, medium-heavy trucks and large sedans. Using a 5.7 would be right in the middle of that range. Think about the GT500's 5.4 in the middle of the 5.0 and 6.2. The only thing different about that situation is that the 5.0, 5.4 and 6.2 are two completely different engines, therefore... one of them are about to "terminated" (pun). GM could cover a 5.3, 5.7 and 6.2 and a fraction of the cost in which Ford does it, the DOHC 6.2 is just way to big to be a sports car engine and a 5.4 replacement will be coming very shortly.

So, a 6.2 carries a 4.065 bore and 3.622 stroke (375.98 ci/6.1623 liter) although it would be even closer as far as valve size though. If we could use the LS7's 4.125 bore to achieve a 6.2, we could use a 3.513 (375.51ci/6.154 liters) to 3.522 (376.47ci/6.170 liter). That would give us enough room for the large valves that would be optimal for high RPM deep breathing. Just some free writing here...

[LOWDOWN]

You're confusing valve size with port size...

You can have a 2.20" intake valve, oversized in a small-port head, where a 2.00" was (theoretically), but it may not flow much more and/or make much more usable power. Made of the same materials, the 2.20 may not rev to the same limits as the 2.00. In fact, a 2.00's revability may allow the engine to make MORE power than the 2.20 might achieve.

Taken in the other direction, if you increase port size to flow more (to accommodate the bigger valve), you may in fact decrease port velocity at part-throttle, thereby disturbing the intake mixture to a less-than-ideal combustible state and dropping power while increasing emissions...less efficiency can be the result, caused by lower port velocity. What works great at 7,000 rpm may be terrible at 2,500...even with VVT...

Ford learned this many years' back with their street-version Cleveland heads...the smaller-port 2V heads were preferred for the street over 4V or BOSS versions..."port velocity"... The same lessons learned by Chev with "peanut port" Big Block heads vs. large-port versions in less-than all-out, steetable set-ups.

Again, what works at the track does NOT necessarily translate "inch-for-inch" on non-track engines that you'll see coming out of Oshawa or Bowling Green on production line-built engines/vehicles...

The Gen-V version will ultimately have several head-port, valve-size configurations available (just as LS-versions have now), but extreme port-valve combos will not likely be assembly-line available. As with the LS and other SBC versions, the Aftermarket will provide many answers GM can't/won't offer.

Remember, CAFE '16 approaches...

[thePill]

Originally Posted by LOWDOWN

Your "theory" here is based on all-out rpm/racing...which ISN'T the stated purpose, day-in and day-out of ANY regular production engine...especially with design features and technology necessary for TRUCKS, the overwhelming volume-required use for this architecture.

This would be a Z28 engine, most "day-in and day-out" practices can be left at the door. Air flow is the single biggest concern in a 2 valve engine when race level RPM's are concerned. Heads that are designed with superior intake ports mated to a high rise intake would only be restricted by maximum valve capabilities. Lift and duration could be an easy fix, but once VVT comes into play, could be very complicated. We already see a huge .591 lift in the LS7 and a 2.20 intake valve just to supply the engine what it needs at redline. If you really think about it, a .591 lft and 2.20 intake is pretty extreme. The Z28 will have a race engine in it.

Cylinder head tech. will be slanted, generally, to TORQUE as opposed to HP...where velocity is most important. Think "small port" vs. "large port"... Small for trucks and "regular" passenger requirements with low- and mid-range usage (generally), large(r) for performance applications. Emissions and fuel economy will be at least as important as all-out rpm/power. And at lower speeds, TORQUE moves the "load". More torque, less pedal...less emissions...less fuel consumption. And THAT'S where VVT (regardless of methods used) will have its every-day applications.

Let VVT worry about emissions, if an LS7 can pass then a Gen V w/VVT can. There might be circular ports on this generation V8, the ports were blocked in the pictures of the LS5.5 but of course that could change.

Performance applications? Time the VVT, and design the cylinder heads, accordingly. With 7- and 8-speed trannies for both emissions and CAFE compliance at part-throttle.

Easy on the 7 and 8 speed transmissions for now. I would rather these guys (Ford included) maximized the engine's capabilities first before they take the expensive and heavy way out. VVT is a very powerful weapon against emissions and fuel economy.

BTW, contact LPE or Katech and request 3.8" worth of valves in your 3.98" bore LS1...ain't gonna happen...

That is probably correct, although we are talking about an advanced cylinder head design and not the LS1. The LS1's intake would max out a 2.05 and would start to shroud at 2.08. The stock exhaust was 1.55 and if I remember correctly, they could be taken out to 1.61. That was at a 15 degree valve angle though putting us at 3.66 combined valve radius and not to shabby for a 3.89 bore (0.23 of play). Working with the LS7's 4.125 bore and a 2.20i/1.61e for a combined valve radius of 3.81 (w/ a 12 degree valve angle) gives us a 0.315 play area at the valves widest point, much more than the LS1's.

...and all other things being equal, which they never are, an over-square engine (bigger bore than stroke) will out-rev an under square one (stroke bigger than bore) every time. Compare the characteristics of a 302 (Z/28) to a 307 long-stroke... Bore makes rpm, stroke makes torque.

This is true, a smaller/lighter crank directly benefits the reciprocating motion of the pistons, lighter/shorter rods creates a lighter, internal drivetrain and those two things combined increases RPM's.... However, if the size of the piston becomes so large, as most OHV's are, it will begin to diminish any returns a small, lightweight internal drivetrain would produce. It is also the initial flaw of the pushrod design, as it presents numerous parasitic losses in those moving parts and fails to maintain positive valve control at high RPM's... This design is also limited by a single intake and exhaust valve, so where the internal potential for higher RPM's exist in the bottom end of an over square setup, those advantages are immediately defeated by the top end by design. This is why I believe that a square (or at least close to it) bore/stroke could benefit in an OHV design that would see an increase in RPM's through mass and rod length reduction in the internal drivetrain and an increase in valvetrain speed with shorter pushrods via the raised cam.

Very good conversation by the way....

[thePill]

Originally Posted by LOWDOWN

You're confusing valve size with port size...

You can have a 2.20" intake valve, oversized in a small-port head, where a 2.00" was (theoretically), but it may not flow much more and/or make much more usable power. Made of the same materials, the 2.20 may not rev to the same limits as the 2.00. In fact, a 2.00's revability may allow the engine to make MORE power than the 2.20 might achieve.

I am using the LS7's intake valve size of 2.20, If your referring to the circular ports I was talking about. I meant circular vs. the rectangular ports that are commonly used. There was a small write up about the differences that I will post later. DOHC's are using an O port instead of a rectangular port, I will put it up if I can find it again... I would like to get the valve's discussed in full first.

[LOWDOWN]

You can change valve timing with VVT. But you have to "optimize" valve SIZE to "port dimensions"...which are predicated by overall volumetric efficiency and port velocity at a given rpm. What, therefore, is our intended rpm range? Knowing, of course, that what's ideal at off-idle and low/mid-range will NOT be "ideal" at high(er) rpm...and the REVERSE is true, too.

Unless/until someone finds a relatively inexpensive way of varying engine displacement and/or port size (length AND cross-section) while the engine operates, all the pertinent factors required to make a streetable engine efficient at ALL engine speeds is a compromise...

[LOWDOWN]

Originally Posted by thePill

We already see a huge .591 lift in the LS7 and a 2.20 intake valve just to supply the engine what it needs at redline. If you really think about it, a .591 lft and 2.20 intake is pretty extreme. The Z28 will have a race engine in it.

A .591" lift cam in a 427" is no problem. A .591" lift cam in a 376" (or less) is extreme. I built a 346" LS6 with LPE's GT1-1 cam....631" lift...that idled like Jason Line's Pro Stock...and wasn't even close on emissions. Big-ass cams need big-ass cubes, on the street...VVT or NO VVT...

As for a Z/28 coming from Oshawa with a "race engine" in it, "I don't think so, Tim..." Emissions-compliant, and CAFE-friendly, my friend.

[thePill]

Originally Posted by Blizzard

Doing some research says we dont see a C7 until 2013 model year so still 2014 model year for Camaro wich most likely means alpha platform to help meet Cafe standards

Sorry for the late reply, I was locked into a technical discussion but, I think the time frame that most insist on is correct. I believe GM said that the C7 would be out in model year 2013, so calendar year 2012 is when we will see both the C7 and the Gen V engine at shows. Camaro fans should be praying for GM to break the usual route, as in Corvette/Camaro leap frog. A simultaneous C7/Z28 release would really draw some attention in the summer of 2012. Will GM break tradition? This would be the first time (that I know of) that GM played both aces.

[thePill]

Originally Posted by brandotron

And we've seen engine changes mid-generation on the Camaro before. Cool thread. I've been hearing about this forever, but this is the first I've seen of it.

Ah, good point. I can't say for sure what years those were but I think I remember GM doing that for the Camaro. Things I would be interested to see:

1. At what point in the year those changes were made? Was it a mid-model update?

2. How long was the Corvette offered with the engine prior to the Camaro receiving the sudden change.

3. What was the sales and performance situation compared to the competition before the updates?

4. The engine offering before the change and the performance gained after the fact.

5. What were the physical changes to the engine, were the changes improvement to the current design? (LS1>LS2>LS3) or was it a new engine altogether (LT5)

6. Where was the Camaro at in its model life when this/these mid-model year drivetrain upgrade(s) occurred?

Just trying to see if there are any circumstantial coincidences that maybe could indicate an action like that in the future. Sorry for the late reply by the way and thanks for reading man...

[thePill]

Originally Posted by LOWDOWN

You can change valve timing with VVT. But you have to "optimize" valve SIZE to "port dimensions"...which are predicated by overall volumetric efficiency and port velocity at a given rpm. What, therefore, is our intended rpm range? Knowing, of course, that what's ideal at off-idle and low/mid-range will NOT be "ideal" at high(er) rpm...and the REVERSE is true, too.

Unless/until someone finds a relatively inexpensive way of varying engine displacement and/or port size (length AND cross-section) while the engine operates, all the pertinent factors required to make a streetable engine efficient at ALL engine speeds is a compromise...

The target RPM range would depend on the size of the engine, I would love to see a 5.7 liter Z28 but that's just me. If a 5.7 was what we were shooting for, I could easily see 7200-7400RPM's (factory limited). We would be more focused on a gradual, steady power curve with horsepower peaking within that 7200-7400 range. Torque should be typically higher, (and I will use the Boss 302 for the benchmark) because of the larger bore of 4.125.

First let me get these Boss 302 measurements up (nearly square)
Bore: 3.629 inches
Stroke: 3.649 inches
Our 350 has a 3.27 to 3.279 stroke and that's where our RPM's are coming from. I need to figure out a way to paper calculate peak horsepower and torque. I would have to guesstimate a compression ratio (going to go with 11:1) and cylinder head volume (the LS7's 70cc and work down from there)... I would actually need quite a few measurements to be honest. Isn't there a guy on here that has a computer program that can run performance simulations with some of those measurements? The Hot Rod PC guy.

Edit: A quick calculation based on a 4.125x3.27 and 70cc heads gives me a 10.22:1 compression ratio. Using the max stroke of 3.279 gives me a 10.25:1 compression ratio. I need to look into head gaskets and pistons/rings now. LOL!!! I'm working with a paper thin gasket at the moment, I will need to make up the lost compression with a thicker gasket with the piston/ring setup.