Not get this started but...
1) Overhead cam vs. push rod for power/torque depends on the cam profile and
nothing else. Use the same cam profile in each, and they will make almost
exactly the same power (frictional loss accounting for the difference). The
valves could care less how they are being opened and when and how much the
valves are opened is all that matters for power.
2) Flexibility is the key with a motor, and ideally the torque curve should
be flat across the RPM band. No one likes a pushrod motor that weases like a
pig at 4000RPM so that you have to constantly shift, just like no one likes
a OHC motor that has to be wound up to 6000RPM to make any power.
3) The need for valve timing is not constant; more overlap can produce more
power at higher RPMs but blows for drivability at lower RPMs. OHC motors
make variable valve timing practical as the cams are "out of the motor". So
both low end torque and high end power are possible.
4) Power is a function of how much air goes through the motor. There are
only a limited number of ways of getting more air through a motor:
- make it bigger (more CID)
- make it rev higher
- forced induction
Rev it higher obviously produces less low end power than make it bigger
(more air per RPM in the bigger motor). Once again the valve actuation
method has nothing to do with any of these, other than OHC motors have lower
reciprocating mass, so its possible to "rev it higher".
So, whats the answer? A big ass DOHC supercharged and turbocharged motor
with variable valve timing and NO2 :-)
Craig
-----Original Message-----
From: SuperNagz@aol.com [mailto:SuperNagz@aol.com]
Sent: Monday, July 26, 1999 7:05 PM
To: dakota-truck@buffnet.net
Subject: DML: 4.7L vs. 5.2L settled!
3 words to settle the 4.7L vs. 5.2L debate:
4.6L vs. 5.0L
I hate to bring up Fords.. but, all in all.. a motor is a motor... more
specificaly.. a pushrod motor is fairly similiar to another pushrod.. and..
a
cammer to a cammer (single)
Anyways, Dodge is now doing what Ford did a few years back. (needless to
say,
this is WHY I started buying Dodge)
Pushrods will always be superior to cammers when it comes to heavy
vehicles/trucks, and/or performance machines.
The Ford 4.6 that replaced the 5.0 was only good for two things... fuel
economy, and part complexity reduction- Ford replaced nearly all their big
engines with overhead cammers with many interchangable parts)
Those two things mentioned above are great for the car company... saves them
money, and makes them look good on the fuel economy.
When it comes to performance... pushrod will just blow away the cammer that
replaced it. Gobs of lowend power... and we all know that thats all that
matters. Who cares if an overhead cammer has say 250 hp at 6,000 rpms...
think about it.. that engines STILL has to rev across that entire
underpowered rpm band to get to that high peak rpm.
On the otherhand... the pushrod monster has instant power off the line...
sure... a pushrod will run out of steam sooner than the cammer.. but who
cares, by then, you've shifted to the next gear, and your back at your lower
rpm/monster power range
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