C6 Z06 vs. FGT vs. SRTC. *Edmunds review*

Orr89rocz

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^ well i'm running 245/50/16's on my iroc

later this summer i'll be switchin to 275/40/17's up front and either the same on the rear, or 315s. i want the wider tires. this spring i'm jumping up from 3.27's to 3.42's

i'll see what gas mileage i get and we'll compare it. cuz 245's to 315's is HUGE
 

Jman20427

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Formula51 said:
I think we will certainly find out how strong or weak this engine is. There are already various cam's in development and talk of spinning the engine to 7500 and possibly even 8000rpm (very questionable in my opinion, based on the extreme piston velocities). It will be interesting to see if the LS7 is as strong as the LS1, LS6, and LS2. My gut tells me maybe not, but I would hope GM torture tested the hell out of this thing because lots of engine failures would be very bad for their reputation and that of future high performance Corvettes.


If GM is thinking about making a cam that can rev in the 7500-8000 RPM Range, that is Very Very Very Questionable. The LS7 will not(IMO) with stand a 8k redline reliably with a cam swap and nothing else based on Maximum and Average Pistons velocities.

Average Pistons Velocity is stroke x RPM/6. So a 4.0 stroke LS7 at 8000 would have an average speed of of 5333 ft/min. That it higher then a F1 engine (around 5200)! And you would need a very very stable valvetrain to keep those numbers, which the Z06 does not. Close, but not quite. Not to mention it is going to take some serious heads to flow at that range, which even with the heads on it now, its iffy. Not to mention some serious lightweight pistons. It can be done, but in the end, to have that car redline at 8k is going to take alot of money for it to be doable, alot more then just a cam swap.
 

Formula51

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Jman20427 said:
If GM is thinking about making a cam that can rev in the 7500-8000 RPM Range, that is Very Very Very Questionable. The LS7 will not(IMO) with stand a 8k redline reliably with a cam swap and nothing else based on Maximum and Average Pistons velocities.

Average Pistons Velocity is stroke x RPM/6. So a 4.0 stroke LS7 at 8000 would have an average speed of of 5333 ft/min. That it higher then a F1 engine (around 5200)! And you would need a very very stable valvetrain to keep those numbers, which the Z06 does not. Close, but not quite. Not to mention it is going to take some serious heads to flow at that range, which even with the heads on it now, its iffy. Not to mention some serious lightweight pistons. It can be done, but in the end, to have that car redline at 8k is going to take alot of money for it to be doable, alot more then just a cam swap.

I completely agree with you and I mentioned the same thing about the high piston velocities earlier, but regardless there is talk of it. We shall see. I too have my doubts.
 

Orr89rocz

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ls7heads flow pretty good. the exhaust side needs work but the heads support intake lift to .700+ lift. stock cam is .600. Ls7 with some valve train upgrades should support 8000rpms
 

Jman20427

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Orr89rocz said:
ls7heads flow pretty good. the exhaust side needs work but the heads support intake lift to .700+ lift. stock cam is .600. Ls7 with some valve train upgrades should support 8000rpms


I think the heads will need a little more umph then what they have if they wanna support an NA cam that goes at 8k. Even with valvetrain upgrades and support to .700 lift, you need alot of CFM out of those heads to get that baby moving at 8 thou. Im not sure off hand what they flow out of the box. Dont get me wrong, the car will go fine at 8k with these heads, but to maximize the cam potential, you need more, like 350+, probably more.
 
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Formula51

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E. Green Cobra:

Look up the weight of the Viper tires and wheels vs. the Z06 tires and wheels so we can have something to go on. I did it for the gears and it turned out you were wrong.

I have never said the LS7 is SOLELY the reason for the better gas mileage, just that it is a major contributing factor. The larger tires and increased weight will have a "slight" effect on the Viper, but I believe it to be insignificant and we have to have some numbers to try and figure it out.

We are talking about 6MPG highway, that is NOT a small amount. And 4MPG city is not that small of an amount either. "slightly" larger tires and 200-300lbs of weight just are not going to account for 6mpg at highway speeds no matter how you slice it. That is what I am trying to tell you. I would argue that the larger tires and higher weight probably account for the Vipers better gearing. Thus, the majority of the difference is in the engines and tunning.

I wish we had engine dyno tests of fuel consumption over a period of time at a given rpm for each engine, but we dont. Who knows, I'm sure that info exists, but we may not be able to see it.

To say the engines in these two cars are not major contributing factors to the miles per gallon achieved by them just does not make sense.

I don't understand why you will not give credit where credit is due.
 

GTSpartan

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Jman20427 said:
I think the heads will need a little more umph then what they have if they wanna support an NA cam that goes at 8k. Even with valvetrain upgrades and support to .700 lift, you need alot of CFM out of those heads to get that baby moving at 8 thou. Im not sure off hand what they flow out of the box. Dont get me wrong, the car will go fine at 8k with these heads, but to maximize the cam potential, you need more, like 300+, probably more.


Yeah, as sweet as that motor is, it will take some major work to hit 8k. That's hella lot of rpm for a motor that size. Also, try shifting a syncro tranny at that rpm :nono:
 

Formula51

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Jman20427 said:
I think the heads will need a little more umph then what they have if they wanna support an NA cam that goes at 8k. Even with valvetrain upgrades and support to .700 lift, you need alot of CFM out of those heads to get that baby moving at 8 thou. Im not sure off hand what they flow out of the box. Dont get me wrong, the car will go fine at 8k with these heads, but to maximize the cam potential, you need more, like 300+, probably more.


I believe they flow over 300cfm stock.
 

Jman20427

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Formula51 said:
I completely agree with you and I mentioned the same thing about the high piston velocities earlier, but regardless there is talk of it. We shall see. I too have my doubts.

Yep, I guess you could say I was further solidifying your statement. But I was also just baffled to hear that GM would even try such a thing. Especially if they market them. People start buying and motors start going= More bad news for GM and their flagship car.
 

Jman20427

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GTSpartan said:
I believe they are in the ~350 range on intake

Yeah, quick google Check and many posts seem to concur with an average of 360 CFM @.591 and 214 on the exhuast. Quite impressive on the intake side. Sounds like the heads are up to the task to breathe *farily* well at 8k, however that exhaust side is killer, and like you said GT, the tranny wont like that to much.
 

Orr89rocz

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^ yeah the intake side is amazing

the exhaust side tho is abit weak... i think the heads have a 69% exhaust intake ratio which isnt very impressive and it will require a large split duration cam. hence the stock cams 211/230 degree duration setup.

the heads should support 8K rpms but like you said, only with the modded valvetrain and internals. stock it can rev to 7K so i'm sure 8 wouldnt be out of the question

heres some info on the head flow
http://www.ls1tech.com/forums/showthread.php?t=438754

looks like 360ish/240's not bad from a production head. thats more than ported LS1/Ls6 heads
 

satx

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Orr89rocz said:
^ yeah the intake side is amazing

the exhaust side tho is abit weak... i think the heads have a 69% exhaust intake ratio which isnt very impressive and it will require a large split duration cam. hence the stock cams 211/230 degree duration setup.

the heads should support 8K rpms but like you said, only with the modded valvetrain and internals. stock it can rev to 7K so i'm sure 8 wouldnt be out of the question

heres some info on the head flow
http://www.ls1tech.com/forums/showthread.php?t=438754

looks like 360ish/240's not bad from a production head. thats more than ported LS1/Ls6 heads

Not bad for a production head? How about that is rediculous for a production head.......even for a 4V head (at least on the intake). On the flip side the heads have been CNC'd at the factory and there won't be much left.
 

GTSpartan

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satx said:
On the flip side the heads have been CNC'd at the factory and there won't be much left.

Not exactly true, the intake could still take some and the exhaust side could take a good amount of porting
 

E. Green Cobra

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Formula51 said:
E. Green Cobra:

Look up the weight of the Viper tires and wheels vs. the Z06 tires and wheels so we can have something to go on. I did it for the gears and it turned out you were wrong.

I have never said the LS7 is SOLELY the reason for the better gas mileage, just that it is a major contributing factor. The larger tires and increased weight will have a "slight" effect on the Viper, but I believe it to be insignificant and we have to have some numbers to try and figure it out.

We are talking about 6MPG highway, that is NOT a small amount. And 4MPG city is not that small of an amount either. "slightly" larger tires and 200-300lbs of weight just are not going to account for 6mpg at highway speeds no matter how you slice it. That is what I am trying to tell you. I would argue that the larger tires and higher weight probably account for the Vipers better gearing. Thus, the majority of the difference is in the engines and tunning.

I wish we had engine dyno tests of fuel consumption over a period of time at a given rpm for each engine, but we dont. Who knows, I'm sure that info exists, but we may not be able to see it.

To say the engines in these two cars are not major contributing factors to the miles per gallon achieved by them just does not make sense.

I don't understand why you will not give credit where credit is due.
I'm not taking anything away from the LS7, it is obviously a beast, I feel however that the gas mileage is due more from the total configuration, I was under the impression you were saying it was more the LS7, perhaps I read a post wrong, or it was another person... I'll look for wheel weights on the two vehicles when I get a chance....BTW I never said the Vette had better gearing(than the viper), I said it had good gearing (specifically the two overdrive gears, its hard to argue with a .50 6th gear), I was aware of the overall gearing of the two vehicles....it would be nice to have complete information on the consumption rates, but its not a big deal....
 

Jman20427

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satx said:
Not bad for a production head? How about that is rediculous for a production head.......even for a 4V head (at least on the intake). On the flip side the heads have been CNC'd at the factory and there won't be much left.


Actually, theres still room left over to port those babies. 375 can be obtained quite easily, and a more radical job can net you 390+. Just because it is CNC ported, does not mean there wont be much left. This thought was first raised when AFR first came out with the heads for the 5.0 motor. There were CNC ported and everyone thought that you couldnt get much more out of them. But it was found that you most definetly could.

Edit: Sorry GT, didnt see your post!
 

Orr89rocz

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Not bad for a production head? How about that is rediculous for a production head.......even for a 4V head (at least on the intake). On the flip side the heads have been CNC'd at the factory and there won't be much left

check these flow numbers on 2 and 4 valve heads and tell me if they look good. i thought they would be higher than that. other values for chevy heads are good so these are probly correct.
http://users.erols.com/srweiss/tablehdc.htm#Ford

seems to me ohc heads dont flow all that much better than ohv heads that are set up right. in this case the LS7 head is substantially higher than even ported 4v's. the only thing i can see is ohc heads haveing better exhaust to intake flow ratios.
 

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Orr89rocz said:
check these flow numbers on 2 and 4 valve heads and tell me if they look good. i thought they would be higher than that. other values for chevy heads are good so these are probly correct.
http://users.erols.com/srweiss/tablehdc.htm#Ford

seems to me ohc heads dont flow all that much better than ohv heads that are set up right. in this case the LS7 head is substantially higher than even ported 4v's. the only thing i can see is ohc heads haveing better exhaust to intake flow ratios.

I would agree that the LS7 head outflows many 4V designs, but if you are trying to say that a 2V OHV design is superior you are mistaken.

4V OHC > 2V OHV

Just think if chevy dropped some 4v OHC heads on that 7.0L displacement and rev'd it to 8k.


BTW, what was this thread about?
 

Orr89rocz

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comparsion of the Z06, to Ford GT, and Viper i think. but this is about the Z06 now which is good for info in comparison of the cars


anyway, if 2 valve ohv designs flow more and make more power, then how is 4v OHC motors/heads any better? flow makes power. i dont care how it gets in there, as long as it mixes with fuel and burns well. only thing about OHC is less parts up there and they can rev. also they seem to have better low lift flow numbers to a point to comparable flowing 2 valve OHV heads. but when setup right, OHV seems to be unbeatable. no need for super high revs when you can make that power abit lower rpms with more cubes. i see no need for GM to pursue OHC designs. Ls heads are the main reason for the power behind the Lsx's.
 
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