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Pushrod engines, why?


Mensan

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Are we still living in the stone age? Sure they are inexpensive, but I think there's a reason for that. Pushrods and 2 valve heads suck, my 4 valve heads flow more stock than most ported 2 valve heads. AND they dont need to shape the port around some weak ass pushrod. Have fun with this one.

 

Old guys, defend yourself...

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Guest BLACKBIRD99
Cheaper/easier to work on. Plus, pushrod motors are proven to have better low end power. Oh yeah, and my "ancient" pushrod motor is still getting 20+ mpg on the hwy. Not bad for 380+rwhp.
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Your heads are HUGE

 

You have to spin 4 heavy cams in your valve train.

 

Your engine is heavy as shit. (because of your massive heads)

 

There are 3 and 4 valve heads for pushrod motors.

 

A small block can fit in almost any engine bay, your DOHC needs a VAST amount of space.

 

DOHC technology has been around since the early 1900's, so what's "old tech?" (So have hybrid cars for that matter)

 

If it's so much better then way does a Mustang need a blower to make as much power as a n/a LS2?

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One word... TORQUE! Now if they were to use one set of valves for low RPm then, progressively bring in the second set, that would own the pushrod motors.

 

But look at bikes, rice burners turn silly RPM's are all OHC or DOHC motors. Harleys, V-twin, pushrod design, and really only need two gears to run, startout and drive. Try to start out in 3rd on a rice burner then go right to 5th or 6th. It's out of the hole slow, then it finally gets fast, then you shift. THen it's slow to acclerate again. Do the same thing on a Harley, it will pull out reasonably hard, then continue pulling after the shift. What I am getting at it a broader torque curve.

 

For that matter, what even happened to the powerglide. It went the way of high compression musclecar motors with carbs. The torque hopped a plane and left Detroit, and is finally trying to return, on the wings of computer controller high compression motors once again.

 

One day there will be electronic valves, and then we WILL have the best of both worlds. But until then. They both hav a place, just not in my driveway.

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Originally posted by desperado:

One day there will be electronic valves, and then we WILL have the best of both worlds. But until then. They both hav a place, just not in my driveway.

We've already got VtEc Yo!

which is pwned by VVT-i

 

VVT-i > vtec > 4.6 > pushrods

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How heavy is that engine? How many did they actually make in Mustangs?

 

Good try, but that was limited production and didn't sell terribly well. I will give ya this though, the 5.0L Cammer Crate Motor is badass, but it's not production and costs more.

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Originally posted by Mallard:

How heavy is that engine? How many did they actually make in Mustangs?

 

Good try, but that was limited production and didn't sell terribly well. I will give ya this though, the 5.0L Cammer Crate Motor is badass, but it's not production and costs more.

the LS2 isn't even on sale yet... tongue.gif

 

the n/a 4V motors in the cobra and mach 1 held their own against the LS1 f-cars. i'm sure the new mustangs/cobras won't disappoint either... smile.gif

 

[ 02. August 2004, 02:11 PM: Message edited by: recklessOP ]

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um...no. GM's best motor has to be the LS series of engines. The LS6/LS2 has as much to more power as the ZR1, and it's still a small block and doesn't cost an arm and a leg. The small block makes more power then the Mustang in a more compact package. You may think pushrods are old architecture, but the LS engines are some of the most advanced engines technologically. Overhead Cam architecture has been around just as long.

 

I'm not comparing the old 2V 4.6 to the brand new LS2, I'm comparing whats currently on sale. Whats the horsepower rating of the MACH1 compared to a Z06? How bout a new Cobra to a new Vette? How much rotational inertia is in your valvetrain?

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Originally posted by Orion:

wow, i fucked up and ended up in the tech section. i knew i should have taken that left turn at alba-...wait a sec, this IS the flame room.

 

just without flames.

 

 

god this is weak.

Shut up nutswinger!

 

better?

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Originally posted by recklessOP:

i'd be happy with double that... :D

Buy a bike, or shorten your stroke to the point where you have not powerband until 7000 rpms.

 

Who gives a shit how many rpms the engine turns if you can't use the entire rpm range?

 

*Interesting fact of the day* F1 engines turn nearly twice the rpms's as NASCAR, but they both have the same mean piston speed.

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By the time you build a pushrod motor right, you made the ports all big and lost that precious low end torque anyway.

 

Back in the real world, you trade torque for horsepower and RPM in order to win races. Even in pushrod series like NASCAR and NHRA. The only way around that tradeoff is to add inches, spray or blow it.

 

Those 4v mod motors come out of the box with some nice ports. Too bad the motors are the size of elephants and their valvetrains cost more than the GNP of Sri Lanka (sorry Morgan! tongue.gif ). Packaging and cost are their biggest downfalls. Ford ought to also gear their cars right, then people would whine less.

 

Speaking of gears, man, I can't believe the "torque, torque, torque" crowd is forgetting all about gears. What's the first thing you do when you take your pushrod motor and give it a bunch of port and cam? Maybe put gears in it? Do you think that the Fords like some gear? :D

 

Getting back to what sucks about DOHC on a V motor -- four cams is a mess. The timing chains on those cars are 50 feet long or something, and I'm sure that it's a whole day's entertainment to swap cams and time them. A cam swap on a pushrod motor is a quick and simple way to really make some power, but on the Ford DOHCs, it's an investment requiring a second mortgage and a large check to Hensler.

 

So, sum it up like this -- look at the Ford Racing catalog, and look at two engines: 5.0 pushrod and 5.0 cammer. Dollar for dollar, you can make probably make as much or more power with the pushrod. BUT...for a set displacement, you are going to make more power PERIOD with the DOHC.

 

Anyone think that there is a reason why no racing series on earth has pushrods and DOHC competing at the same displacement?

 

The world doesn't live around dollar for dollar, though. When you lose a race, you can't whip out parts receipts saying "Well, I spent less money!" That's as lame as the ricer bullshit about cubic inches.

 

Oh, interesting story about why the LS1 wasn't made as a DOHC motor. GM prepared two test mule Corvettes -- one with a prototype pushrod engine, the other with a prototype DOHC. They then let a bunch of executives drive them around the proving grounds and decide which one they liked better. The execs picked the pushrod motor, so it was decided to make the LS1 pushrod.

 

Note that engineers did not decide this. Racers did not decide this. Even Corvette buyers did not decide this. A bunch of grey-haired 50-60 year old men who spent their careers at such automotive giants as Proctor and Gamble decided this. :rolleyes:

 

Credit GM engineers with making a fine motor anyway. You can't help but wonder what might have been, though.

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Ok Mark, what advantage does DOHC give an engine when it's not utilizing variable valve timing? Are you claiming that the port shape of the DOHC motor is superior to the pushrod counterpart? Is having all that extra rotational mass in the valvetrain really worth it if you're not varying cam timing over the rpm range? Do you think that DOHC is used in racing series because they're better at high rpm's, or do you think the DOHC make them faster? I'd like to hear your reasoning.
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