Good point. AFAIK, there are no multiple-valve OHV engines (yet).
However, 2 valves per cylinder is certainly not the death knell that
some make it out to be. Witness current offerings by Chrysler and GM.
I basically agree with everything you've said, but keep in mind that I
only said that the OHC design doesn't have a _clear_ advantage. It can
be argued that the DOHC is more complex and has more moving parts to
wear out and/or break, thereby possibly negating the advantages of the
extra valves per cylinder.
All things considered, current technology enables OHV and OHC engines to
be on par with each other. I believe it all comes down to preference.
The two valve engines make for good low end torque numbers. They can't
hang with the high end breathing and high rpm redline potential of an
OHC engine without some very expensive machining and/or compromises in
low end performance. Matching VVT with a multi-valve OHC engine makes
for some very potent potential regarding hp/torque across the entire rpm
range to well over 7,000 rpm. IMO, Ford is getting hp from their
modular motors very easily where GM and Chrysler can only get high hp
numbers from their OHV engines by increasing displacement. Making hp
through sheer displacement isn't that difficult or impressive, IMO.
Saying that, don't forget I plan to put a 427W in the old Mustang. ;)
This is where I have to disagree. I think the OHC engines are less
complex and are more reliable due to their design. Look at the
complexity of the VVT on the OHV engines. If they ever get multi-valve
technology then they will be even more complex. Whether these OHV
engines with VVT are durable remains to be seen. We know for certain
VVT is durable on OHC motors. One of the major problems for any OHV
engine is the frailty of push rods, lifters and rocker arms. This is a
lot of moving mass to account for, especially in the upper rpm range.
The OHC engines don't have this issue. Although they may be percieved
as more complex I think they are actually simpler. We perceive them as
complex because we think it is new technology. It really isn't. All
you have to do is look at the track record of the OHC engines in the
cars that use them. It is stellar. The 4.6L is proving to be even
more durable than the 302 and that is saying something.
I agree. The one big advantage I see with OHV engines is their smaller
size. Take that away and, IMO, there isn't much of a reason for their
existence in today's automobile world.
If I had my druthers I would LOVE to stuff an '03/'04 Cobra motor with a
Kenne Bell blower on top into the engine bay. The 427W is easier and
less expensive but, make no mistake, the Cobra motor would bitch slap it
HP/liter means something when talking about an engine's power production
efficiency. A Viper engine weighs in at about 650 lbs. and a Z06 at
about 460 lbs. The 4.6L weighs in at around 440 lbs. The Ford Triton
V-10 weighs in at 635 lbs. fully dressed. I will give you that the
external size of OHC engines are greater than OHV engines. The weight
looks to be nearly equal.
" Here is the latest info... 5500 produced in 2008, they will be
SRT8's only w the 6.1L hemi and AutoStick Transmission.
2009 they will have a 3.5L V6, 5.7L Hemi, and 6.1L Hemi w/ Optional
6-Speed Manual. Looks like it will be very close to the concept.
Different wheels and a few small changes but overall it is pretty
Pictures and conjecture at:
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.