Point/Counterpoint: DOHC v OHV

[KILLSHOTS]

Originally Posted by Mystic ZR-1

And I suppose you FEEL Elvis and Hitler are still alive?

As I'm sure you can tell, I'm simply illustrating the absurd by being absurd. FEELING that a certain engine is reliable - or that a certain one isn't so - does not make said feeling even remotely true.

[Meanmyz]

I don't really have time write, but will punch this out now anyhow...

I just got back from Arnold, Nebraska on Sunday night. This is the area where the Sand Hills Open Road Challenge was held as well as the Loup to Loup road race. They also had half mile and one mile shootouts.

The winner of the one mile was a modified 2004 Lamborghini putting out 2000 HP. It ran a best of 228 mph through the mile. ...that is another story.

There were three ZR-1's running. They were all modified 350's and I am not sure to which degree. One '90 ZR-1 had Marc's 350/510 package...his actually said 350/515. I believe his one mile run was at 160 mph... that was on older Borla mufflers. The others averaged around 157 mph.

There were three new C7 Z06's there with very experience drivers. A friend of mine had one of them and it has the Z07 package. He had removed the rear wicker extensions from his spoiler.

His car was the fastest of the new Z06's. What did he run??? He was around 165 mph through the mile! He was only five miles per hour faster than the fastest ZR-1!

The stock C6 ZR1's ran faster than the new Z06's.

That is not a put down to the Z06, but there are some issues out there yet for the new car. The Z06 drivers said their car fell flat when hitting fifth gear.

Is this all the aero/down force bits on the car??? Or is this a tuning, supercharger heat issue? I don't know.


One poster here seems down on our "old" ZR-1's. Yes, we are not in a vacuum, but don't cut the ol' LT5 short!

When building the LT5, Chevrolet didn't reverse engineer every part to the cheapest price per widget before failure. They went with world class suppliers on a "we are going to show the world" basis that had the bean counters screaming.

I like the new Corvettes. I like old Corvettes. But, don't deny it... The old ZR-1's are a special breed. Our LT5's don't drop valves. Another friend is scared when his C6 Z06 warranty will go off. Is he going overboard? Maybe. But in the end, I am proud of my LT5!

[edram454]

???? what is he talking about?? decided to feel??? the lt5 did pass the 200 hour durability test and did set the record at nearly 176 mph for 24 hours. You dont have to feel it. It is what it is. How about the lt4?? Has it done anything or set any records?? I am perplexed to hear people trying to poke holes in the lt5 on this forum. This is one place I thought that most people would be in agreement but guess not. If its a joke I dont get it. whatever.

[Meanmyz]

In re-reading my earlier post now, I just wanted to add...in the shootout, the cars each got three runs. The cars mentioned all had very consistant runs. I am not sure how much difference it makes, but the 1990 ZR-1 mentioned had the "ballast" of a passenger. Not sure about the others.

Oh, I was there as a navigator for the road races. Maybe I will enter next year.

[XfireZ51]

Ed,

I started this thread as a means of discussing the pros and cons of the different engine architecture with their inherent advantages and disadvantages. I'd like to keep this on a technical level if possible. Many of us are fans of the C4 ZR-1 due to the unique power delivery we get from the LT-5. Many would like to see GM re-create that and believe that DOHC should be the future direction for Corvette in order for it to take its place among world-class automobiles. So far, GM doesn't seem to agree but they have also done a heck of a job refining the OHV architecture. My premise is that as good as the LT4 platform is, it's near topping out due to inherent limitations.
So your thoughts?

[mike100]

Originally Posted by XfireZ51

Ed,

... Many of us are fans of the C4 ZR-1 due to the unique power delivery we get from the LT-5. ...

I don't know when GM will break away from OHV V8's, but I feel it is somewhat on topic to point out the LT4's deficiencies as not a totally improved product while we all wish for something a little more exotic. My biggest point is the fact that there were a ton of you tube vids from week one that showed just about everything handing the new Z06's azz to it on roll races. Then came the GM apologists etc...

My take is that GM is holding back...way back... the engine only has a 1.75l supercharger that has to spin faster than the previous ZR1's LS9 unit which was 2.3l. I think it is blowing hot air and running with more internal parasitic drag. All the new cam phasing, direct injection, and all of that just to get the same power as the LS9??

Makes you wonder what the mid cycle refresh is going to bring.

[WVZR-1]

Originally Posted by mike100

Makes you wonder what the mid cycle refresh is going to bring.

Every LT4 out there is doing the "dependability/reliability" R&D for the corporate folks. The future?

[XfireZ51]

Originally Posted by WVZR-1

Every LT4 out there is doing the "dependability/reliability" R&D for the corporate folks. The future?

Frankly, I learned my lesson when I bought a brand new 1984 C4 4+3 Z-51. Love the car,
BUT I won't do that again.

[Mr Blue]

Originally Posted by mike100

I don't know when GM will break away from OHV V8's, My take is that GM is holding back...way back...
Makes you wonder what the mid cycle refresh is going to bring.

GM made a decision for the C5 to develop pushrod V8s and abandon the LT5. Much has been said whether or not that was the correct decision. People have pointed to the power levels of present day LSx engines and said it was the right decision. That can not be established from the data. They can rightly say that their program has been successful and they have achieved good gains in power. However the LT5 was, at the time of the decision, a viable 400+ HP engine.. It took GM 10 years of development to regain that level of power. Further increases came with increases in displacement and FI. All of us know that the existing LT5 was capable of much more. We would all like to have seen what development of the LT5 would have wrought. The supposed superiority of OHV engines in my mind is answered by the racing classes that do not penalize any valve configuration. In those classes OHC engines are dominant. The lone exception is unlimited drag racing. All that being said, we can and do enjoy the unique position that the ZR-1 hold in the Corvette lineage. It does not have to compete with a 25 year newer car. My hope is that GM corrects the LT1/LT4 problems soon. If they are holding back it's not working. Maybe they will adapt OHC heads to the latter block, but I doubt it.

[XfireZ51]

If you want an idea of where the LT-5 could have gone, just look at the Gen2 prototype Graham Behan discussed. 475hp without any displacement increase. And that was 25 years ago. Look at what Mercury Marine is doing with a VERY similar platform. They learned their lesson. If I was GM, I would be partnering w them on "productizing" the LS/LT block w the MM DOHC cylinder heads.The demise of the LT-5 was a combination of "penis envy" on the part of the Powertrain guys, and bean counter myopia from the green eye shade people.
Both of which I think we have seen too often from the RenCen and Warren.
I hope Mary Barra is changing that.