7.0L Development Motor!
Posting Guru
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i think ford needs to return at least its powerhouse (F350, f450) trucks offer an engine with pushrod design, modular engines are great for a balance between a useable power band and fuel economy + emissions control...but pushrod design has so much better power to offer, a fuller longer power curve...
Postmaster
Joined: Feb 2003
Posts: 4,074
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From: Las Vegas
Originally Posted by godblessmud
..but pushrod design has so much better power to offer, a fuller longer power curve...
Like a motor has any clue where its cam(s) are located concerning powerband.
Where do people come up with this stuff??????
Laughing Gas
Joined: Mar 2006
Posts: 1,164
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From: Tri-Cities, TN
Originally Posted by DOHCmarauder
Like a motor has any clue where its cam(s) are located concerning powerband.
Where do people come up with this stuff??????
Hotshot
Joined: Jun 2003
Posts: 12,360
Likes: 4,394
From: SW VA
I also highly doubt we will ever see this in a production vehicle (much less a truck). It might...might, be offered as a crate engine.
I don't see the HP wars comming back with the strict emissions control and the gas prices the way they are.
I don't see the HP wars comming back with the strict emissions control and the gas prices the way they are.
Postmaster
Joined: Nov 2004
Posts: 2,511
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From: Marion, VA
Originally Posted by DOHCmarauder
Like a motor has any clue where its cam(s) are located concerning powerband.
Where do people come up with this stuff??????
Emissions is what is killing big blocks. To get the same power out of smaller engines (for emissions), you have to get it at higher RPMs. Push rod engines has so much more reciprocating mass that OHC is the logical way to go.
Postmaster
Joined: Feb 2003
Posts: 4,074
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From: Las Vegas
Originally Posted by osbornk
Very true. I guess they don't recognize that most pushrod engines are very large. Size does matter. When towing, there is no replacement for displacement.
Emissions is what is killing big blocks. To get the same power out of smaller engines (for emissions), you have to get it at higher RPMs. Push rod engines has so much more reciprocating mass that OHC is the logical way to go.
Emissions is what is killing big blocks. To get the same power out of smaller engines (for emissions), you have to get it at higher RPMs. Push rod engines has so much more reciprocating mass that OHC is the logical way to go.
Originally Posted by snowdog79
I can't imagine where people get this stuff either! Bore/stroke ratio, compression, programming, etc. are what make a difference in power delivery. OHC designs have the advantage of lower reciprocating mass and the easier adaptation of four valve heads and variable valve timing, although both are possible with OHV motors too, it's just harder to do. (For a OHV motor with variable valve timing, check out the new Viper V10).
Reciprocating mass is a viable debate.
I believe that a pushrod motor may actually have LESS RECIPROCATING mass if it's a V type motor...and also an inline motor with DOHC has an extra cam to turn.
The debate is whether pushrods are considered reciprocating.
In theory, pushrods are a detriment as far as valvetrain stability.....but GM LSx motors seem to have a handle on that.
I don't don't think there is any debate that multivalve technology most certanly benefits from DOHC architecture......
I've always thought the 2 valve wedge SOHC MOD motor to be more complicated then it needed to be.....but it was a stepping stone to later 4 valve (and goofy 3 valve) designs.
Last edited by DOHCmarauder; Oct 5, 2007 at 04:25 PM.
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Postmaster
Joined: Nov 2004
Posts: 2,511
Likes: 0
From: Marion, VA
Originally Posted by DOHCmarauder
Reciprocating mass is a viable debate.
I believe that a pushrod motor may actually have LESS RECIPROCATING mass if it's a V type motor...and also an inline motor with DOHC has an extra cam to turn.
The debate is whether pushrods are considered reciprocating.
In theory, pushrods are a detriment as far as valvetrain stability.....but GM LSx motors seem to have a handle on that.
I don't don't think there is any debate that multivalve technology most certainly benefits from DOHC architecture......
I believe that a pushrod motor may actually have LESS RECIPROCATING mass if it's a V type motor...and also an inline motor with DOHC has an extra cam to turn.
The debate is whether pushrods are considered reciprocating.
In theory, pushrods are a detriment as far as valvetrain stability.....but GM LSx motors seem to have a handle on that.
I don't don't think there is any debate that multivalve technology most certainly benefits from DOHC architecture......
Posting Guru
Joined: Jan 2005
Posts: 1,574
Likes: 0
From: Seattle
Off topic for a moment (Fred)...
So where the heck has NumberDummy been???
The dude went from like 29 posts a day, to NO posts in the last three weeks?.........freaky.
Bill, are you and your manuals out there.........?
So where the heck has NumberDummy been???
The dude went from like 29 posts a day, to NO posts in the last three weeks?.........freaky.
Bill, are you and your manuals out there.........?
Postmaster
Joined: Feb 2003
Posts: 4,074
Likes: 1
From: Las Vegas
Originally Posted by osbornk
Back in my wasted youth, the debate was between OHV and flat head motors. OHC were only found in exotic European cars and Fiats. I found out early that OHV engines don't like high RPMs. You would get valve float and sometimes bent pushrods. I think the pushrods, rocker arms and lifters held the valves open at high speeds because the spring had to push them back in addition to closing the valves.
Right on.....it's known as valve float. And like you said, it's the inability of the spring to close the valve. Modern tech and lighter valve trains have allowed higher RELIABLE revs with pushrods than ever thought possible.
And TRUE OHC designs actually have the cam lobe DIRECTLY on top of the valve stem.....adjustment is done by shims between the two.
Most of the automotive OHC designs use a rocker or finger follower so that a hydraulic plunger or lifter takes up the slack. In other words, the cam lobe does NOT act directly on the valve.
The new Ford 3.5L V6 in the Lincoln actually uses a lobe on tappet method....supposedly no need for adjustment for at least 150,000 miles.
Most high performance DOHC bilkes also use this method......but adjustments are more frequent.
Last edited by DOHCmarauder; Oct 5, 2007 at 07:45 PM.
Lead Driver
Joined: Jul 2007
Posts: 7,868
Likes: 9
From: Rhode Island
Originally Posted by osbornk
Back in my wasted youth, the debate was between OHV and flat head motors. OHC were only found in exotic European cars and Fiats. I found out early that OHV engines don't like high RPMs. You would get valve float and sometimes bent pushrods. I think the pushrods, rocker arms and lifters held the valves open at high speeds because the spring had to push them back in addition to closing the valves.
Postmaster
Joined: Feb 2003
Posts: 4,074
Likes: 1
From: Las Vegas
Originally Posted by Lead Head
What is high RPMs defined? 5k, 6k, 13k?
I know you didn't axe me but solid lifter BOSS 302's could rev to 7,000 RPM but needed constant valve adjustment.
Modern day OHV motors run around 6,000 RPM safely.
DOHC motors run 7,000 RPM PLUS with a lot of the limitation being the accessories running too fast!!!
Torrque and low speed power is dependant on filling the cylinder quickly....that's why big, slow revving motors make all their power down low and then basically run out of breath,
What's cool about VVT is you can "restrict" the opening which speeds up cylinder filling making a smaller motor have decent low end.....then as the revs rise, open up the lift/duration to let all the air the motor can handle in for that top end charge.......much easier to do using VVT with multivalves.
Look at the Tundra motor some time (sorry for the blasphemy) every bit as much low end torque as the 5.4 Ford with over 100Hp more at the rear wheels.
And Ford has just as many resources/parts to do it also!!!
decadent and depraved
Joined: Jan 2005
Posts: 6,703
Likes: 6
From: Right Behind You
Originally Posted by RocketScience
Off topic for a moment (Fred)...
So where the heck has NumberDummy been???
The dude went from like 29 posts a day, to NO posts in the last three weeks?.........freaky.
Bill, are you and your manuals out there.........?
So where the heck has NumberDummy been???
The dude went from like 29 posts a day, to NO posts in the last three weeks?.........freaky.
Bill, are you and your manuals out there.........?
Tim
