ZL1 v GT500

Why don't drag cars use ohc engines, if there so good at everything? Ever head one of those rev up? It's up and down to idle faster ten you can blink, and turns 8k rpm. NASCAR engine turn over 9k rpm for hours on end during a race.. Ohv don't rev??

Ferrari's rev because of their small components. Tiny pistons, ity bitty little cams, light weight everything. Build a 6.0l liter Ferrari engine and see how high you could rev it.

 

Americans cars don't have weak blocks. The new cobra block will hold a TON of whp the last ones held easily 1000hp with built internals no issue. Furthermore the LSX series of motors are very strong while weighing pratically nothing. If Im not mistaken a shortblock which is a motor without heads or accessories weighs in at 350lbs. This is why they are so common in swaps no matter what the origin of the shell is.

 

Lee actually has a point. The race OHV engines out there are milled out of a single block, and the tolerances are extraordinarily tight. They are high tech, and built to a price. With that said, the durability standards of American engines far out-perform that of most of the european performance competitive counterparts.

 

Say what you will, except for the 427 in the ZO6 they really are not great, kinda vibratey and while the power is there they are slow to respond and kinda thrashy. Plus the rev range is limited and if you do actualy drive on the track a broad powerband makes a huge difference.

The Mustang motor by comparison is considered sweet and a free rever.

While I drive neither of these at the track, I do track a lot and there are several mustangs and camaros that show up. I can say that around the bends the current camaro(ie not zl1) is a bloated pig, and reall just an obstacle to get around,(and some are modded and supercharged) while the mustangs at least seem the be driven far harder, maybe it is the drivers eact type attracts. Neither one really corners. The only fast newer mustang I have seen around the track was the laguna seca edition running slicks.

The fast street cars that I see running around the track are Ferrari 458's Porche Gt3's Nissan GTR's ZO6 vettes and lotuses and maybe the laguna seca mustang. . All the other street cars that I see(including new M3's, various porches) are way off pace whether running slicks or not.

Stripped and Moded e36 BMWs are fast but tracked out cars are a different category.

To really run hard at the track you need light weight, great brakes that hold up, and power helps but not necessarily in abundance. The GTR is the one car that gets away with the weight, but they also struggle to hold up doing hard laps on a hot day. A heavier car is also going to eat a lot of tires and brakes.

BTW I hear that if youre going to seriously consider tracking a porche GT3 figure $1500 per day in consumable and maint, lord knows what a 458 costs to track. Lets see how the ZL1 and GT500 hold up and do around the bends when people start to track them.

The appeal of detroit iron on the track is things like brakes wheels and tires are going to be so much less than running a porche or a ferrari, plus the upfront cost is way lower for an out the box "track capable" car. The downside is a lack of finesse precision and refinement which can detract from the driving pleasure.

Seems to me that if your going to track, a laguna seca mustang or vette pref a zO6 are great domestic products, and the vette is objectively pretty hard to beat.

 

yea i've been planning on buying a second car next year. the practical side of me says "get a 4 door car, you can keep it for 20 years and grow into it with a family, etc." the 27 year old male in me says "boss 302 mustang... now. keep it forever". i may do both, just not sure which one first lol

 

Get the mustang, there is plenty of time to be stuck in a 4 door. Sometimes loife, wife kids negate getting that fast car, so buy it and keep it if the opportunity is there now.

 

Point is if youre going to be fast on the road/track light weight and broad powrband is the way to go, along with compact design.

Drag cars like boats have different engine requirements, as do aeroplanes. The ZL1 and to a lesser extent GT500 claim to be track capable cars.

 

Pushrod vs OHC


"Mercury Racing president Fred Kiekhaefer says that the QC4v project sprang from the reality that pushrod big-block V-8s have reached their limits, power-wise. "The valvetrain is the weak link at these power levels," Kiekhaefer says. "When you get into the really high loads, it's hazardous duty for the valves and springs. We've built 2000-hp pushrod V-8s, but they're not pretty for very long."

So Mercury Racing engineering director Erik Christiansen got to start with a clean sheet of paper for the new monster motor. The original target was something in the 1250-hp range, but dyno tests revealed that there was more power to unlock. "The engine was just so happy at that power level that we realized we could get more out of it," Kiekhaefer says. "The air got down into the cylinders and said, 'Wow, I've never had an easier time getting into a combustion chamber.' " And that's surely the last thing the air said"

 

Great discussion

I wanted to check a few facts so I called my freind who races drag cars nationaly and is a shop owner for these engines.

Drag engines are mostley Billet. These engine which do 2500 to 2800hp are machined out of a solid chunk of virgin Billet. I assumed aluminum probably T6 or better but I did not ask him.

They use push rod desings because they need the valve lift to be excessive, about an inch of lift plus or minus. Do do excessive lift and to make it easily adjustible at the track, they employ two fulcrums.
One is the cam which is machined in and the rocker arms which can be changed in the field easily for track conditions. My freind says most drag blocks have multiple rockers lengths or lifts to chose from.

I asked him about sand cast versus investment cast. I knew in the past what a wrote was true but things change as technology moves ahead and may have changed. He feels the same way I wrote my initial discussion, He indicated several of the lower drag classes still use sand cast motors becuase they and can be replaced cheaply. he also said even the lower drag classes have become more competitive and some of the better financed teams are starting to move to investment cast. They are still alot cheaper than his $250k motors to race in the upper classes.

He also indicated that OHC motors go as high as 20k RPMs red line where OHV engines about 5.8k or less max rpms.

Lee

 

the more i think about it, the more that^ makes sense. "get your toys now" has always been what dad has told me :stirthepot:

 

http://www.caranddriver.com/features/flat-out-we-gun-for-200-mph-in-the-2013-ford-mustang-shelby-gt500-feature

I have my own theories as to why; namely how heat-soak kills it at a certain point in a high speed run. You cannot simply just run with that much heat building up and that much velocity on the rotors like you can on a slower turning supercharger, or a more aerodynamic, and better cooled vehicle. You have one opportunity with each run to hit 200 with an engine like this.

 

Wow, fascinating! Thanks for the info.

 

http://www.camaro5.com/forums/showthread.php?t=236658
Post # 154:
After waiting most of today, I decided to give the dealership service manager a call to see about any progress. He informed me that the car has not been looked into, let alone worked on since last Friday. He was in contact with the GM service manager, who authorized the order of a replacement crate motor, which he was quite certain didn't include the supercharger assembly. He said that delivery would be either Thursday or Friday from somewhere in Ohio.

I asked if the engineer previously consulted or any engineer was coming to the dealership and what he responded was quite shocking. The GM engineer he had talked with said explicitly, "The LSA engine block has known porosity issues and an engineer doesn't need to oversee the process." Given the fact that the service tech found no existing bulletins on any source of oil leaks in a ZL1 or LSA motor, it seems like Chevy and GM are trying to keep secret what is internally a known issue.

I asked about getting the damaged exhaust replaced, as can be seen in the photos on page 1, the oil did quite severe damage. The dealership service manager said he inquired with the GM service manager about replacement, and he responded toward the side of cleaning it. At this point, I think that the oil burns on the exhaust warrant a replacement along with another new flywheel if scoring is present, which I stressed to the service manager.

With the delivery date of sometime this week, the estimated time of repair (best case scenario) is set at next Wednesday. By which the car will have been in for service 21 days of the 40 since I took delivery. It will be interesting whether this porosity issue rears its head anywhere else or if GM does already know the situation and is trying to keep it as quiet as possible. At this point, I am at the mercy of GM and as many people have pointed out, they seem to be trying to resolve my problem as cheaply as possible.

 

How does a push rod engine have "both less reciprocating weight and less initial resistance to deal with"???!!....an OHV engine eliminates push rods & lifters & rocker arms that equals LESS reciprocating weight than a push rod engine & also LESS initial resistance....Mark

 

I can NOT think of "1" performance handling car with a SOLID AXLE!!!....the Mustang GT 500 has a SOLID AXLE!!!....WAKE UP FORD!!!!!.....Mark

 

Please explain to me....how less moving parts ( OHC) motor can weight MORE than a motor (OHV) with MORE moving parts....with everything else being equal...as far as initial resistance....lifters in a bore cause resistance, rocker arms on a rocker shaft cause resistance, pushrods cause resistance....an OHC motor eliminates those resistances...eliminate moving parts (friction = resistance).....Mark

 

Really sorry to hear about this. You buy your dream car, there is a problem and then you get jacked around by GM. I mean how much would it cost to replace the exhaust.

On another note you would expect they would wan't the whole engine back, supercharger and all just to see what went wrong. Sadly GM culture is alive and well. Stick it to the customer, repair for a little as possible and take a 2 million dollar pr future sales hit.

This folks is why GM is in the shape its in, its their attitude and no ammount of MBA BS is going to change the facts. What they shouyld have done ius replace the car, at the very least the whole motor assemble and a credit on a future purchase. Then this story would have read completly differently.

BTW saw a Z06 eat a valve at a trackday recently.

 

OHC has fewer "moving parts" yet more moving mass, further away from the center of gravity.

Even if by some miracle, the cam's are ultra-light weight, and the weight of the rods adds up to more weight than the additional 3 cams, the rotational forces on the cam offer greater resistance to motion than the pushrods do... IE one cam = less rotational mass.

It is once the engine is at higher RPM ranges where the advantages of DOHC comes into play with superior fluid dynamics of the inlet, cylinder head, and piston geometries come into play.

The LSa redlines somwhere around 6300 +- where the 5.8 Modular redlines at 7000. HP vs. TQ curves tell a lot about the positives and negatives of each engine's power delivery.

Both are incredibly high tech masterpieces of high production

 

Hello Isaac; That is why I mentioned "All things being equal"....a "single" OHC engine is going to weight LESS than a "single" cam OHV engine.....NOW!!!!...if you bring into the comparsion a "4" valve per cylinder "4" cams DOHC V-8 engine...then "YES" that engine will weight MORE than a "single" cam OHV V-8.....that is why I specified..."All things being equal"...I believe a DOHC engine is Superior to a OHV engine at ALL rpms...superior cylinder head flow/design is superior at ALL rpms....the cam lift/duration determines "How Much".....Mark

 

Please.....4 cams will ALWAYS weigh MORE than 1.....32 valves will ALWAYS weight MORE than 16....even if the 16 valves were titanium...if push rod motors are so effective as you claim, producing as you claim less friction....then why are ALL Indy Car Series motors...Dual Overhead Cam Motors!!???....Mark

IndyCar Series engines are rev-limited to 10,300 rpm and produce approximately 650 hp. The valve train is a dual overhead camshaft configuration with four valves per cylinder. The crankshaft is made of alloy steel, with five main bearing caps. The pistons are forged aluminum alloy, while the connecting rods are machined alloy steel. The electronic engine management system is supplied by Motorola, firing a CDI ignition system. The engine lubrication is a dry sump type, cooled by a single water pump.

 

Yes so a camaro with a Mustang 650 hp motor and mustang weight is goimng to be pretty awesome, plus a decnt inerior. Given the costs of the bits already there such a machine would be a slight prtemium to the current offerings.

There would be no excuses world class. that it does not exist tells you all about how detroit is not only not world class by comparrison but not even world class in its own backyard ie pony cars. They just dont aspire to top standards even though clearly if you look at a CTS(interior) Camaro(styling suspension) and mustang(motor weight) all the bits exist. Maybe the new mustang will hit this sweet spot.

Still it is amazing that detroit which really could lead misses the mark because they "save" $1500 per car in an expensive car where the price sensitivity for the extra $$ is not a factor. Same with the vette. The germans having no such qualms can charge much more than the extra they invest.

Maybe the viper will break the mold, but that 300 crt instrument display says don't hold your breath yet.

Given that at ZR1 costs porche 911 money how about a great interior, great build and possibly an OHC engine. Even a Z06 motor and light weight with superlativer build and inerior.

My opinion, not going to happen. Detroit will always compromise the product just too much so sales are listed as patriotic and bang for the buck, We can do so much better, even the Italians make a great product these days. If we can have a ford focus and a chevy equinox, why not the rest. Come on detroit the consumer may be ignorant but they are not dumb and the japanese are on the ropes and the germans have really high production costs.

Its lack of confidence, poor attitude to product and customer, with a logic that we still need to make cheap crap that holds us back.