[Bhobbs]

Originally Posted by NW-99SS

Will wait and see - I don't see GM building two completely different sets of heads for the same engine family (AKA Blackwing Block)...they may have different flow rates, chamber sizes, valve, etc, but the overall architecture will most likely be the same.

The Blackwing block won't be used if its actually a 5.5 liter engine. The entire Blackwing design was optimized around the 4.2 liter displacement and there is no way to get anywhere near 5.5 liters with it. The 4.2 is already a small bore and long stroke to reduce bore centers.

I'd rather see a clean sheet design with large enough bore centers to get a big bore and short stroke set up, which should rev and breath much better.

[Rodan]

Originally Posted by newmoon

Well it looks pretty quick, definitely faster than the R.

Always difficult to tell from video, but it appears the GT350 is carrying more midcorner speed than the GT500... that would make sense with the weight numbers. But it doesn't bode well for beating a ZLE...

Can't wait to see an unbiased shootout...

[BlaqWhole]

Originally Posted by RobbyBeefcake87

You're comparing a 15k crate engine to engines that are north of 70k. Not exactly apples to apples.

That is what I was trying to tell him.

Originally Posted by Martinjlm

The question then becomes, why didn't GM and FCA go to turbos instead of SC? I think the answer lies in the fact that they had not yet gone to DI at the time that they started boosting their V8s. Look at what GM did choose when they started adding power to DOHC engines. 3.0TT and 3.6TT versions of the HFV6 for Cadillac, as well as the 2.0T for Pontiac Solstice and Cobalt SS.

In V6 and I4 applications I do believe that DOHC engines are superior due to size limitations. Even if a DOHC V6 is larger in size than a pushrod V6, the extra HP they are capable of making by far outweighs the size disadvantage. In that case that is a clear nod for DOHC. And I would never argue that.


However I believe those advantages start to wane and ultimately disappear once you get into V8s and displacement can be exploited. DOHC engines seem to be limited to around 5.5 when it comes to what you can stuff into a car realistically. Although the S197 GT500 was a 5.8. There is a 6.2 DOHC out there but I doubt those engines are practical for street use and I really doubt they would end up in a car. Back to the point. Where a DOHC V6 clearly outpunches the pushrod V6, the DOHC V8s struggle to keep up with the pushrod V8s as we have seen. And the cost factor is still there.

So it isn't a power or efficiency thing because we've seen some of the fastest cars with the most powerful engines all using a pushrod setup. The only answer that I have heard is that the Euro market taxes based on displacement and GM has to comply. Therefore since they are limited in displacement they have to go with a 5.5. Basically the pushrod engine is getting handicapped from it's advantages and that is why we'll be seeing DOHC engines in the future.

Originally Posted by IneedAZ

Funny how since the announcement of the C8, it seems like nobody is talking about what is next with the ZL1 anymore. If by 2021 there is no plans for an engine upgrade i will go C8. I still plan to mod the 17 ZL1 and get rid of the Mopar.

ps...Chevy needs a better sound system...I still find my Harmon Kardon in the Dodge way better.

I think it's more because the C8 just took the world by storm and is the most exciting thing going on right now. GM could drop the LT5 in the ZL1 now and everyone would still be talking about the C8, lol!!

Originally Posted by L78toLT1

Completely agree. No doubt that engine packaging is easier with OHV motors vs. DOHC. Engines are also lighter, cheaper, and less complex. However, if size/packaging is not an issue, DOHC is the way to go. How many pushrod 4 cylinder's do you see these days?

This seems to be the answer. Not that DOHC engines are better. But that displacement is being capped or taxed and manufacturers have to limit the engine sizes.

[BlaqWhole]

Originally Posted by shaffe

I guess we can agree on that, but maybe the people telling you DOHC are better suited for turbo applications are on to something because there are no modern pushrod turbo set ups lol



I said I don't know from an OEM stand point. All I said was that if turbos were that much more expensive than superchargers why is every automaker using them. I also said I am not sure on the upkeep.



I am with you there. If I was building a car it would be blower all the way, but that is mostly because I love the supercahrger whine lol. Agreed on the factory set up




This is where I disagree with you. You have been given answers why DOHC is better for a TT. The answer is in the 4V head design commonly found in DOHC set ups. Martin and Whiteboy both confirmed this. Turbos use exhaust gasses, DOHC have dedicated exhaust valves, gives the OEM better platform to tune both engine and turbo for max driveability and performance than a 2V pushrod would... That is what makes a DOHC set up better for turbos from an OEM standpoint

There has not been one answer from anyone who outright said that DOHC engines are better than pushrod engines when both setups can be used to their advantages. The only answer that resonates is that the Euro market taxes on displacement and therefore GM has to switch to DOHC since they are limited on how much displacement can be used. That basically goes with everything I've said from the start. That if you handicap the pushrod engine and exploit the DOHC engine's advantages, then that is the only time a DOHC engine would be better.

But to be fair, I asked if anyone could prove that a DOHC engine is superior when both engine's advantages and disadvantages are explored and not one person answered that a DOHC engine is better.

[crysalis_01]

Why can't we just do both, large displacement WITH dohc?

https://www.mercuryracing.com/mercur...-crate-engine/

Benefits of the DOHC four-valve design versus the typical LS pushrod layout include:

•Improved intake and exhaust flow enables increased engine performance
•Efficient, high tumble four valve combustion
•Low mass, high stiffness design reduces stresses and enables smooth high RPM operation and long life
•Improved drivability due to optimized camshaft timing at comparable horsepower levels

[Martinjlm]

Originally Posted by BlaqWhole

There has not been one answer from anyone who outright said that DOHC engines are better than pushrod engines when both setups can be used to their advantages. The only answer that resonates is that the Euro market taxes on displacement and therefore GM has to switch to DOHC since they are limited on how much displacement can be used. That basically goes with everything I've said from the start. That if you handicap the pushrod engine and exploit the DOHC engine's advantages, then that is the only time a DOHC engine would be better.

But to be fair, I asked if anyone could prove that a DOHC engine is superior when both engine's advantages and disadvantages are explored and not one person answered that a DOHC engine is better.

Originally Posted by crysalis_01

Why can't we just do both, large displacement WITH dohc?

https://www.mercuryracing.com/mercur...-crate-engine/

Benefits of the DOHC four-valve design versus the typical LS pushrod layout include:

•Improved intake and exhaust flow enables increased engine performance
•Efficient, high tumble four valve combustion
•Low mass, high stiffness design reduces stresses and enables smooth high RPM operation and long life
•Improved drivability due to optimized camshaft timing at comparable horsepower levels

The answer to both of these questions is pretty much the same. Fuel economy and emissions. There IS a replacement for displacement. It’s called boosting. I’m not certain that there is any advantage to OHC or OHV when it comes to supercharging, because that is primarily providing a mechanical boost. But the main emphasis to creating power is creating maximum airflow. That’s what turbochargers do. They push more air per cycle through the combustion chamber. By virtue of 4 separate camshafts (2 intake / two exhaust) and 4 valves per cylinder (two intake, two exhaust) engineers have more levers to pull to calibrate a turbocharged DOHC engine for max fuel economy, max performance, or optimal mixes of the two in between. That’s how you can get a Malibu 2.0T with 250 hp with 26 mpg combined EPA or a Mercedes CLA 45 AMG with 2.0T making 421 hp. If you just go max displacement with naturally aspirated DOHCs (Voodoo) you can get outstanding performance. But if you back off of the displacement and add boost (Ferrari 3.9TT V8 / McLaren 3.8TT V8) you can get a bit of both.

For the Ferrari and the McLaren, fuel economy may not be the issue so much as emissions. The bigger the holes, the more stuff you have to clean up when it’s all said and done. Ferrari and McLaren have to engineer to the really tough Euro 6 emissions standards, as well as have fuel economy measured on the WLTP fuel consumption standards. Much more difficult than the proposed US standards, including California. Smaller displacement is just the beginning of what they have to do to get there. There is a reason most European car brands offer 2.0L 4-cylinders, 3.0L 6-cylinders, and 4.0L 8-cylinders. They are trying to economize engineering effort to meet these restrictions by developing around 0.5L cylinder sets. That way, the same solution that works for a 4-cylinder can be scaled up to work for an inline 6 which is basically the 2.0L 4-cyl with two more cylinders added.

[BlaqWhole]

Originally Posted by Martinjlm

The answer to both of these questions is pretty much the same. Fuel economy and emissions. There IS a replacement for displacement. It’s called boosting. I’m not certain that there is any advantage to OHC or OHV when it comes to supercharging, because that is primarily providing a mechanical boost. But the main emphasis to creating power is creating maximum airflow. That’s what turbochargers do. They push more air per cycle through the combustion chamber. By virtue of 4 separate camshafts (2 intake / two exhaust) and 4 valves per cylinder (two intake, two exhaust) engineers have more levers to pull to calibrate a turbocharged DOHC engine for max fuel economy, max performance, or optimal mixes of the two in between. That’s how you can get a Malibu 2.0T with 250 hp with 26 mpg combined EPA or a Mercedes CLA 45 AMG with 2.0T making 421 hp. If you just go max displacement with naturally aspirated DOHCs (Voodoo) you can get outstanding performance. But if you back off of the displacement and add boost (Ferrari 3.9TT V8 / McLaren 3.8TT V8) you can get a bit of both.

For the Ferrari and the McLaren, fuel economy may not be the issue so much as emissions. The bigger the holes, the more stuff you have to clean up when it’s all said and done. Ferrari and McLaren have to engineer to the really tough Euro 6 emissions standards, as well as have fuel economy measured on the WLTP fuel consumption standards. Much more difficult than the proposed US standards, including California. Smaller displacement is just the beginning of what they have to do to get there. There is a reason most European car brands offer 2.0L 4-cylinders, 3.0L 6-cylinders, and 4.0L 8-cylinders. They are trying to economize engineering effort to meet these restrictions by developing around 0.5L cylinder sets. That way, the same solution that works for a 4-cylinder can be scaled up to work for an inline 6 which is basically the 2.0L 4-cyl with two more cylinders added.

I don't think I'm asking my question the way I want to. So I will explain it a different way.

Here is what I see.

The move to a DOHC twin turbo setup to me does not seem to be a necessity given the advantages/disadvantages of it vs the advantages/disadvantages of a supercharged pushrod setup. These pros/cons include HP, TQ, efficiency, cost, maintenance, physical size, displacement, overall performance. I don't see GM ever saying "hey guys, we can't make any more power out of these supercharged 6.2 liter pushrod engines so we HAVE to switch to a DOHC TT setup". The switch seems more like they are being forced to do so based on a market they are trying to reach. Or a market that they have to satisfy. Displacement being taxed is the only explanation I could see for them having to switch. Because like I said, we have 6.2 liter supercharged pushrods engines making 650, 707, 717, 755, and 808/840 HP. Now if the market that GM has to reach limits displacement to, let's say, 5.5 liters, then GM would have to switch to a DOHC setup since a 5.5 DOHC would have more potential than a 5.5 pushrod. Catch what I'm saying? I'm saying that GM is not switching from 6.2 supercharged engines to 5.5 DOHC TT engines because the latter is a better platform when all the pros and cons are explored. They are switching because they have no other choice. Otherwise they would have switched a long time ago.

So that is my point. And that is why I there has not been one answer from anyone to prove that DOHC engines are better than pushrod engines when both setups can be used to their advantages. If there was no cap on displacement and if the Euro market wasn't as influential on engine types as they are then GM would not be changing things.

[Martinjlm]

BlaqWhole,

There is not a ceiling on displacement. In China and in some countries in Europe there are displacement taxes. If there was a cap there would be no V12 Lambos, or Rolls Royce’s or V10 Audi R8. The issue is for mainstream cars which constitute the majority of most manufacturers portfolios. So the VWs, Audis, and even BMWs and Mercedes of the world have learned to develop engines that get best hp/l. That gets them to DOHC. And also to diesel. Many of the really impactful technologies in modern gas engines started as diesel technologies. Direct injection, turbocharging, multi-event injection, increased compression ratio.

The other part of the equation, which you seem to be setting off to the side, looms much larger. The serious move to more strict fuel economy and emissions regulations is driving automakers to produce smaller, more fuel efficient and power efficient engines. The one place where displacement makes a definite difference, beyond the issue of displacement based taxes, is emissions. The bigger the hole, the greater the emissions and the challenge to clean them up.

That’s why I am very certain that the next wave of engine development is smaller engines with stronger electric motor assist. And, as has been stated before, to get the most power out of a given displacement, DOHC is the way to go. Also, the flexibility provided by cam phasing, valve timing and valve lift and airflow management is simpler to achieve with multi-cam multi-valve engines. Again, an advantage for DOHC.

If all GM has to be concerned with was making the highest powered engine they could fit under a hood, supercharged OHV makes a lot of sense. But they have to do that while meeting stringent fuel economy and emissions regulations. DOHC engines with variable valve train technology provides a better option to achieve that.


***EDIT*** "for" not "over"

[shaffe]

Originally Posted by BlaqWhole

I don't think I'm asking my question the way I want to. So I will explain it a different way.

Here is what I see.

The move to a DOHC twin turbo setup to me does not seem to be a necessity given the advantages/disadvantages of it vs the advantages/disadvantages of a supercharged pushrod setup. These pros/cons include HP, TQ, efficiency, cost, maintenance, physical size, displacement, overall performance. I don't see GM ever saying "hey guys, we can't make any more power out of these supercharged 6.2 liter pushrod engines so we HAVE to switch to a DOHC TT setup". The switch seems more like they are being forced to do so based on a market they are trying to reach. Or a market that they have to satisfy. Displacement being taxed is the only explanation I could see for them having to switch. Because like I said, we have 6.2 liter supercharged pushrods engines making 650, 707, 717, 755, and 808/840 HP. Now if the market that GM has to reach limits displacement to, let's say, 5.5 liters, then GM would have to switch to a DOHC setup since a 5.5 DOHC would have more potential than a 5.5 pushrod. Catch what I'm saying? I'm saying that GM is not switching from 6.2 supercharged engines to 5.5 DOHC TT engines because the latter is a better platform when all the pros and cons are explored. They are switching because they have no other choice. Otherwise they would have switched a long time ago.

So that is my point. And that is why I there has not been one answer from anyone to prove that DOHC engines are better than pushrod engines when both setups can be used to their advantages. If there was no cap on displacement and if the Euro market wasn't as influential on engine types as they are then GM would not be changing things.

Ok then, so basically you are asking what makes a DOHC TT engine better than a supercharged OHV engine. That kind of becomes a tricky question because there is so many factors going into it. For just making big power, yep supercharged OHV. Dealing with stuff like emissions , regulations and all that stuff OHC set up is better as Martin sums up pretty nicely below.

Originally Posted by Martinjlm

BlaqWhole,

There is not a ceiling on displacement. In China and in some countries in Europe there are displacement taxes. If there was a cap there would be no V12 Lambos, or Rolls Royce’s or V10 Audi R8. The issue is for mainstream cars which constitute the majority of most manufacturers portfolios. So the VWs, Audis, and even BMWs and Mercedes of the world have learned to develop engines that get best hp/l. That gets them to DOHC. And also to diesel. Many of the really impactful technologies in modern gas engines started as diesel technologies. Direct injection, turbocharging, multi-event injection, increased compression ratio.

The other part of the equation, which you seem to be setting off to the side, looms much larger. The serious move to more strict fuel economy and emissions regulations is driving automakers to produce smaller, more fuel efficient and power efficient engines. The one place where displacement makes a definite difference, beyond the issue of displacement based taxes, is emissions. The bigger the hole, the greater the emissions and the challenge to clean them up.

That’s why I am very certain that the next wave of engine development is smaller engines with stronger electric motor assist. And, as has been stated before, to get the most power out of a given displacement, DOHC is the way to go. Also, the flexibility provided by can phasing, valve timing and valve lift and airflow management is simpler to achieve with multi-cam multi-valve engines. Again, an advantage over DOHC.

If all GM has to be concerned with was making the highest powered engine they could fit under a hood, supercharged OHV makes a lot of sense. But they have to do that while meeting stringent fuel economy and emissions regulations. DOHC engines with variable valve train technology provides a better option to achieve that.

Basically, from what I have learned from the really smart people here is that despite OHC engines being physically larger, the "smaller" displacement can help pass emissions because the things martin mentions above like valve timing, lift and having multiple cams.

[rocket403]

Oldsmobile was set to unleash the W43 on the automotive world for 71 72 but GM changed direction and the work on this engine was shelved. This engine was Hemi and a DOHC 455 so you can have the best of both worlds limiting factor would just be size.

one engine the OW43 was able to get 700hp at 7000rpm

https://www.streetmusclemag.com/news...hat-never-was/

[rocket403]

W43 engine

[Gunkk]

Originally Posted by rocket403

W43 engine

Holy EGR, Batman!

[BlaqWhole]

Originally Posted by Martinjlm

BlaqWhole,

There is not a ceiling on displacement. In China and in some countries in Europe there are displacement taxes. If there was a cap there would be no V12 Lambos, or Rolls Royce’s or V10 Audi R8. The issue is for mainstream cars which constitute the majority of most manufacturers portfolios. So the VWs, Audis, and even BMWs and Mercedes of the world have learned to develop engines that get best hp/l. That gets them to DOHC. And also to diesel. Many of the really impactful technologies in modern gas engines started as diesel technologies. Direct injection, turbocharging, multi-event injection, increased compression ratio.

The other part of the equation, which you seem to be setting off to the side, looms much larger. The serious move to more strict fuel economy and emissions regulations is driving automakers to produce smaller, more fuel efficient and power efficient engines. The one place where displacement makes a definite difference, beyond the issue of displacement based taxes, is emissions. The bigger the hole, the greater the emissions and the challenge to clean them up.

That’s why I am very certain that the next wave of engine development is smaller engines with stronger electric motor assist. And, as has been stated before, to get the most power out of a given displacement, DOHC is the way to go. Also, the flexibility provided by cam phasing, valve timing and valve lift and airflow management is simpler to achieve with multi-cam multi-valve engines. Again, an advantage for DOHC.

If all GM has to be concerned with was making the highest powered engine they could fit under a hood, supercharged OHV makes a lot of sense. But they have to do that while meeting stringent fuel economy and emissions regulations. DOHC engines with variable valve train technology provides a better option to achieve that.


***EDIT*** "for" not "over"

I was enjoying the last few days of my vacation so that is why it took this long to respond. Anyway, Mexico was great to me as always. But I'm back home and it is back to reality.

In reply, when I mentioned a cap on displacement I did not mean that GM could not go over a specific size. I meant that the more displacement an engine has the more they will be taxed on it. When you are mass producing vehicles a taxation of this sort might as well cap your displacement. That extra money is multiplied thousands of times. When these manufacturers discuss budgets and such all that gets counted in. Obviously. And that extra money doesn't just affect the Vette or whatever vehicle they are considering. it affects the entire company since they are looking at things as a whole. So there might as well be a cap on it. I'd wager that this was the intended purpose anyway. But that's a debate for a different day. So basically GM has to stay under a specific displacement to avoid being taxed extra. And even if it isn't ALL countries it certainly is enough that it will affect the entire lineup. Are they going to make specific engines for specific countries? Of course not. I'm not delving into an entire explanation of any of this. LOL!!

Now that we got that out of the way...

Like I said, since GM is now limited on engine displacement (as I explained), then it makes sense that they would switch to DOHC engines and also TT setups for a power adder. TT is the most readily available and used method that cars on this level are using. So to me all of this goes back to displacement limits and popularity of this type of setup among a huge market.

Regardless tho, none of this matters as this is what the future has in store anyway.

Originally Posted by shaffe

Ok then, so basically you are asking what makes a DOHC TT engine better than a supercharged OHV engine. That kind of becomes a tricky question because there is so many factors going into it. For just making big power, yep supercharged OHV. Dealing with stuff like emissions , regulations and all that stuff OHC set up is better as Martin sums up pretty nicely below.



Basically, from what I have learned from the really smart people here is that despite OHC engines being physically larger, the "smaller" displacement can help pass emissions because the things martin mentions above like valve timing, lift and having multiple cams.

Technically I was not asking...it was always a rhetorical question that I was debating. I know how both engines operate including the pros and cons of each. I know both setups including their costs and sizes etc inside and out. And from what I have seen, when everything is factored in, pushrod engines are superior when you can use them to their advantages (displacement) and when space is a limiting factor. When being limited on displacement and/or when it comes to 6cyl and 4cyl turbo engines then I do believe that DOHC engines are more reliable and have more potential.

[BlaqWhole]

Anyway, the dealership called yesterday and left a message saying they want to put my C8 order in by the end of the day today. So it is bye bye to one or both of my current vehicles in the next few months.