[big hammer]

Originally Posted by thePill

There are mnay things wrong with a pushrod engine, the main one being the pushrods themselves. Pushrods rob major amounts of horsepower due to design and add a lot of stress on a single cam. With an OHC, it allows the more delicate camshaft to make direct contact with the rocker arms. This eliminates valve float at high RPMs and allows the engine to spin more freely. Most race OHVs can spin up to 10,000rpm, a race OHC can spin up to 20,000rpm. I understand that a 3 valve OHV can be done, but you are adding more pushrods in the engine and a single pushrod can be responsible for 2-8 horsepower per rod (RPM depending) so naturally, a larger displacement is always needed.

Another big issue with a 2 valve, and in most cases all valve configurations (but more so in a small head OHV) is valve shrouding. This is when your only intake/exhaust valve is in close proximity to the chamber wall. This restricts airflow from sometimes 50% of the valve opening, on an OHC engine, heads are naturally larger so chambers can be designed around this problem and... there are additional valves to aid airflow. DOHC cams are hollow and easy to swap out compared to the old cam in block design. With a timing suppression tool, you can literally change 4 cams in a 1/4 of the time it takes to swap out a OHV cam. There are a lot of additional measures you have to take to get a cam out of the block....

If GM would have stuck with the Northstar, it would have been a fantastic engine and for some reason, Team Corvette took offense to the LT5 since it was built overseas. Besides, if OHVs were really that good, they would have stuck with them across the board...

it's the hydraulic lifters that are the limiting factor in RPM's on a ohv configuration. they pump up at very high rpms holding the valves open, causing "float". there are ways to adjust the lifters differently to avoid this, or just go to a solid lifter.

also, you must not have ever changed a cam in an ls engine. you dont even have to pull off the intake to do it. were not talking about the 1955 small block anymore.

another big plus is it's big cube\compact design, easy to work on and cheap for parts. DOHC isn't all peaches, cream and barbie dolls. they are bulky, cumbersome and expensive to build.

the LT5 powerful engine back in the day, but it was also a troublesome POS.

[truth411]

Originally Posted by thePill

There are mnay things wrong with a pushrod engine, the main one being the pushrods themselves. Pushrods rob major amounts of horsepower due to design and add a lot of stress on a single cam. With an OHC, it allows the more delicate camshaft to make direct contact with the rocker arms. This eliminates valve float at high RPMs and allows the engine to spin more freely. Most race OHVs can spin up to 10,000rpm, a race OHC can spin up to 20,000rpm. I understand that a 3 valve OHV can be done, but you are adding more pushrods in the engine and a single pushrod can be responsible for 2-8 horsepower per rod (RPM depending) so naturally, a larger displacement is always needed.

Another big issue with a 2 valve, and in most cases all valve configurations (but more so in a small head OHV) is valve shrouding. This is when your only intake/exhaust valve is in close proximity to the chamber wall. This restricts airflow from sometimes 50% of the valve opening, on an OHC engine, heads are naturally larger so chambers can be designed around this problem and... there are additional valves to aid airflow. DOHC cams are hollow and easy to swap out compared to the old cam in block design. With a timing suppression tool, you can literally change 4 cams in a 1/4 of the time it takes to swap out a OHV cam. There are a lot of additional measures you have to take to get a cam out of the block....

If GM would have stuck with the Northstar, it would have been a fantastic engine and for some reason, Team Corvette took offense to the LT5 since it was built overseas. Besides, if OHVs were really that good, they would have stuck with them across the board...

False, as you know overseas have taxes on displacement, thus inherently favors OHC.
Also the ability to rev to 20000 rpm is pointless for real work applications. Another thing is you can increase displacement without increasing the size of the motor with ohv, so you don't have to rev to the moon to get performance out of it, so your point is moot. The northstar is a good motor, but nothing compared to the LS2 at the time. Heck the LS3 is a better motor than Ford's 5.0, more power, more torque, less weight and bullet proof durable. IMVHO in N.A. applications a well designed OHV V8 > DOHC V8.

[big hammer]

Originally Posted by truth411

False, as you know overseas have taxes on displacement, thus inherently favors OHC.
Also the ability to rev to 20000 rpm is pointless for real work applications. Another thing is you can increase displacement without increasing the size of the motor with ohv, so you don't have to rev to the moon to get performance out of it, so your point is moot. The northstar is a good motor, but nothing compared to the LS2 at the time. Heck the LS3 is a better motor than Ford's 5.0, more power, more torque, less weight and bullet proof durable. IMVHO in N.A. applications a well designed OHV V8 > DOHC V8.

nope. ford has been playing with a new engine. they call it "green". it has a triple overhead cam and makes 300 hp\ltr n\a and has more low end torque than a duramax. i have seen "green" first hand. "green" trumps anything gm could ever produce.

[Black5thgen]

Originally Posted by big hammer

nope. ford has been playing with a new engine. they call it "green". it has a triple overhead cam and makes 300 hp\ltr n\a and has more low end torque than a duramax. i have seen "green" first hand. "green" trumps anything gm could ever produce.

Maybe they should call it "blue" like a smurf because I think you have about the same chance at seeing either in real life.

[Kyle2k]

Originally Posted by Black5thgen

Maybe they should call it "blue" like a smurf because I think you have about the same chance at seeing either in real life.

Oh man, I wish you could "like" comments on here....

[ffrcobra_65]

Mustang GT500 guys are just excited about this news of 600hp+ GT500 just as we were all ecstatic about the ZL1 when rumors of its production and hp #s came to light. Win for all, Camaro and Mustang fans. Those who hate are just plain wannabe car enthusiasts, period.

[thePill]

Originally Posted by big hammer

it's the hydraulic lifters that are the limiting factor in RPM's on a ohv configuration. they pump up at very high rpms holding the valves open, causing "float". there are ways to adjust the lifters differently to avoid this, or just go to a solid lifter.

also, you must not have ever changed a cam in an ls engine. you dont even have to pull off the intake to do it. were not talking about the 1955 small block anymore.

I agree with everything above although, a solid pushrod is going to bend or break which is why hydraulic lifters were used in the first place... and, are you going to pull the engine to do the cam swap or remove the radiator and hope the grille, rad support or front fascia isn't going to get in the way?

Cheaper? sure, even though the LS3 and Coyote are about the same price out of the box.. My cams are more expensive, for now... but now that I think about it, changing cams isn't really as critical in a DOHC as they were in OHVs. All of the current 9 and 10 second 5.0s are on stock cams.

False, as you know overseas have taxes on displacement, thus inherently favors OHC.
Also the ability to rev to 20000 rpm is pointless for real work applications.

I know there are overseas taxes however, OHCs were used far before the the official formation of the European Union in 1993. Without the EU, there was NO Euro 1, 2, 3 or 4 standards. I do believe that 20,000rpm is excessive, but it does go to show you how much farther a OHC can go without mechanical limitations... The power band on a 20k 400hp engine would be nearly flat. On the other hand, a 10k 400hp engine would have weak points (beginning and end) especially if the valves were floating at higher RPM.

and you talk about less weight, the Coyote weighs 429lbs and has TiVCT, 4 extra cams, 2 timing chains, 2 extra quarts of oil and a larger oil pan. The LS3 weighs 418lbs... The LS3 is also a 3rd Gen LS series engine, the Coyote is a 1st Gen design... Who's to say that Coyote 2 won't be 450hp, 420tq?.. What about Coyote 3 when PTWA liners come in and save another 8lbs and increase output by another 8hp/tq? The LS series engines are at the same point in its life as the SRA is, both doing well, but won't survive another generation.

[ViperTomcat]

Originally Posted by Blue Maro Demon

Like Truth 411 said GM>Ford when it comes to performance cars. Theres a reason everytime you watch Pinks on SPEED and when you go to car shows and drag races Mustangs have a Chevy engine in them-hint its not for giggles and laughs.

Get into the real world and watch drag racing, get into the pits and staging lanes. I have, and let me tell you this honest truth I have seen both Camaros and Mustangs win and never ONCE in the REAL WORLD have I seen a Mustang with a GM engine or a Camaro with a Ford engine.

Most of the stuff on TV is crap, if you havent been in pits, wandered staging lanes and actually raced you are in no position to talk about the "real world" of drag racing.

[big hammer]

Originally Posted by thePill

I agree with everything above although, a solid pushrod is going to bend or break which is why hydraulic lifters were used in the first place... and, are you going to pull the engine to do the cam swap or remove the radiator and hope the grille, rad support or front fascia isn't going to get in the way?

Cheaper? sure, even though the LS3 and Coyote are about the same price out of the box.. My cams are more expensive, for now... but now that I think about it, changing cams isn't really as critical in a DOHC as they were in OHVs. All of the current 9 and 10 second 5.0s are on stock cams.

.

lol did you seriously just compare pulling the engine to having to remove the rad and maybe the grill? holy shit.....

[Crowley]

Originally Posted by big hammer

nope. ford has been playing with a new engine. they call it "green". it has a triple overhead cam and makes 300 hp\ltr n\a and has more low end torque than a duramax. i have seen "green" first hand. "green" trumps anything gm could ever produce.

LOL .. you are kidding yourself if you think GM isn't on the same page ..

Crowley

[thePill]

Originally Posted by big hammer

lol did you seriously just compare pulling the engine to having to remove the rad and maybe the grill? holy shit.....

Most professional jobs pull the engine, backyard jobs pull the radiator.. either way, I will be almost done before you take your intake off.... It also depends on the car...

[big hammer]

Originally Posted by thePill

Most professional jobs pull the engine, backyard jobs pull the radiator.. either way, I will be almost done before you take your intake off.... It also depends on the car...

bullshit you will. changing dual overhead cams in an extremely cramped engine compartment... and again you dont have to take the intake off an ls engine to change the cam. man you are FOS.

[8cd03gro]

Originally Posted by big hammer

it's the hydraulic lifters that are the limiting factor in RPM's on a ohv configuration. they pump up at very high rpms holding the valves open, causing "float". there are ways to adjust the lifters differently to avoid this, or just go to a solid lifter.

also, you must not have ever changed a cam in an ls engine. you dont even have to pull off the intake to do it. were not talking about the 1955 small block anymore.

another big plus is it's big cube\compact design, easy to work on and cheap for parts. DOHC isn't all peaches, cream and barbie dolls. they are bulky, cumbersome and expensive to build.

the LT5 powerful engine back in the day, but it was also a troublesome POS.

Clearance between all of the valvetrain components in an OHV also restricts timing precision at a given rpm, sepcifically higher rpm, in comparison to an OHC configuration. The concentric cam design would be most effective in an SOHC configuration. This would allow for multi-valve(4+) heads, centrally located spark and DI, and dual independent VVT with little added weight as SOHC packaging isn't much larger than OHV.

[big hammer]

Originally Posted by 8cd03gro

Clearance between all of the valvetrain components in an OHV also restricts timing precision at a given rpm, sepcifically higher rpm, in comparison to an OHC configuration. The concentric cam design would be most effective in an SOHC configuration. This would allow for multi-valve(4+) heads, centrally located spark and DI, and dual independent VVT with little added weight as SOHC packaging isn't much larger than OHV.

mechanical clearance on a hydraulic lifter setup is zero, unless you count the small pocket of oil between the lifter piston and lifter body as clearance. and again there are ways around that.