Moser DOHC heads for SBC info..
Eugene Blanchard
My nephew dropped off a stack of old Hot Rod mags and the cover of the
August 1971 issue had a set of Moser DOHC heads for the sbc. There is a
detailed article on the heads inside with quite a few pictures. I kind
of remember that there was a discussion here about OHC heads for the sbc
a while back. So here's some info on the Moser's heads which I don't
know if they ever made it to production:
Developed by Richard Moser (Moser Engine corp) and Harver Crane Jr.
(Crane Cams). 4 valves per cylinder: intake valves were 1.50" dia and no
specs for the exhaust valves. The exhaust cam and intake cam are
identical at 250 deg duration at 0.050" lift and 0.450 lift. Cause there
are separate cams for exhaust and intake, it is easy to change lobe
centers by changing one in relation to the other via the belt drive. Cam
timing is adjustable in 1 1/2 deg increments.
There are no hp figures but according to an intake port flow comparison,
it flows 100 ACFM @ 3" H2O versus 50 ACFM for a stock head and 75 ACFM
for a ported head.
The intake ports are siamesed so there's only 8 intake ports like a
normal sbc and the only intake available was a Moser fuel injection unit
similar to a Hillborn fuel injection. There are 16 exhaust ports - 8 per
side. The eight 1 1/2" exhaust ports are all in a row and they were Y'd
into four 1 3/4" tubes and from there it looks like a normal sbc
header.
The engine becomes very wide. Picture a normal engine and heads and slap
on another set of wider heads on top of the existing heads and put a
huge belt drive on the front where you would normally put your
alternator and power steering pump. That'll give you an idea of how big
it is.
--
Eugene Blanchard
Please change the DOT to . on my return address
(It's there to stop spammers)
http://www.therockies.com/blanchas
J Forbes
Sounds really neat! but I think the aftermarket race heads for
the small block nowadays will easily outflow them...
Jim
Talladega Greg
and small block Chevy & Ford, first link is Chevy small block, 2nd
is main page.
Pretty cool!
http://www.araoengineering.com/Chevy/chevysmb.htm
http://www.araoengineering.com/
Talladega Greg
"J Forbes" <jfor...@yahoo.com> wrote in message
news:3D8752A3...@yahoo.com...
Eugene Blanchard
to a pushrod style? Say you could take the same head and just put a cam
on top. What advantage would it have?
Pontiac in the early 60s developed two overhead cam engines: 389 and a
421 for research purposes. They put the cam in the removeable valve
cover and ran the cams from the rear of the engine. They put in a dummy
cam in the regular spot and hung a gear on the back of it to drive the
overhead cams. So this and the moser's heads has led me to think a bit
about overhead cams.
--
cheflee
overhead cam- less weight, fewer moving parts, no long pushrods to bend or
break. As a general rule, overhead cam engines will rev higher than pushrod
engines.
J Forbes
Which is helpful if you're after max hp (at high rpm).
But I still don't understand why Caddy has a dohc engine for
their luxury cars..and why Ford has ohc engines in trucks. It's
just silly.
Chevy seems to do just fine (they have more power and more
mileage than Ford trucks with comparable displacement engines)
with one cam in the block....
Jim
Ted Spradley
>
> Is there a technical advantage to having an overhead cam engine compared
> to a pushrod style? Say you could take the same head and just put a cam
> on top. What advantage would it have?
Better question is, "why pushrods and rocker arms?" More parts to
manufacture, assemble, and go out of adjustment, and more mass to
accelerate. Disadvantages of overhead cams are larger external
dimensions of the complete engine, and a longer cam chain that adds cost
and noise and can stretch. Alfa Romeo, for example, used two short
chains and an idler sprocket between, which adds cost and complexity and
doesn't reduce noise. Modern OHC engines use rubber cam "chains" to
reduce noise, but they have to be replaced periodically because they
stretch and break, leading to bent valves.
--
Remember, more computing power was thrown away last week than existed in
the world in 1982. -- http://www.tom.womack.net/computing/prices.html
J Forbes
>
> Eugene Blanchard wrote:
> >
> > Is there a technical advantage to having an overhead cam engine compared
> > to a pushrod style? Say you could take the same head and just put a cam
> > on top. What advantage would it have?
>
> Better question is, "why pushrods and rocker arms?" More parts to
> manufacture, assemble, and go out of adjustment, and more mass to
> accelerate. Disadvantages of overhead cams are larger external
> dimensions of the complete engine, and a longer cam chain that adds cost
> and noise and can stretch. Alfa Romeo, for example, used two short
> chains and an idler sprocket between, which adds cost and complexity and
> doesn't reduce noise. Modern OHC engines use rubber cam "chains" to
> reduce noise, but they have to be replaced periodically because they
> stretch and break, leading to bent valves.
The part about more mass to accelerate means you can
theoretically run higher rpm with the overhead came...assuming
that valve float is the limiting factor.
Also, pushrods get in the way of intake ports on most V8 cam in
block engines....but with the tall, narrow ports on the late
model Chevy LS1 type engine, it's not a real concern.
Jim
lifespeed
> Which is helpful if you're after max hp (at high rpm).
>
> But I still don't understand why Caddy has a dohc engine for
> their luxury cars..and why Ford has ohc engines in trucks. It's
> just silly.
>
> Chevy seems to do just fine (they have more power and more
> mileage than Ford trucks with comparable displacement engines)
> with one cam in the block....
>
> Jim
Actually, both Ford SOHC V8's are smaller displacement than the
Chevy's. 4.6L and 5.4L vs 5.3L and 6.0L for the Chevy. I've heard the
4.6L trucks don't get as good fuel economy as the Chevy. Like I said,
the Chev's are still good engines. I suspect a 4.6L may be slightly
overloaded in a 4500 lb truck. My '97 Crown Vic gets 25 mpg at 70 mph
on the highway. Now, If I run at 85+ mph, the economy drops below 20
mpg.
I've always been a fan of Chevy engines. Where else can you easily get
the HP like a Big Block Chevy offers?
That said, I've recently had the opportunity to modify an SOHC 4.6L
Ford. They can be strong engines, and OHC is a huge advantage in
high-revving and reducing friction. It's obvious from the drivers
seat. Ford even makes a DOHC 4.6L V8 with 32 valves. 300 HP.
- Lifespeed
lifespeed
> arao engineering has 32 valve heads for Big Block Chevy & Ford,
> and small block Chevy & Ford, first link is Chevy small block, 2nd
> is main page.
> Pretty cool!
>
> http://www.araoengineering.com/Chevy/chevysmb.htm
> http://www.araoengineering.com/
>
>
> Talladega Greg
Gotta have the overhead cams.
- Lifespeed
Eugene Blanchard
for one about 2 years ago and gathered a whack of info about it. I
posted what I found on my website at:
http://www.therockies.com/blanchas/54pontiac/sprint-codes.txt
--
Eugene Blanchard
rockers and roller cams are to pushrod cams? My understanding is that a
roller cam with roller lifters and rockers will gain about 40 hp from
reduced friction.
--
J Forbes
>
> Is there an advantage to an overhead cam of reduced friction like roller
> rockers and roller cams are to pushrod cams? My understanding is that a
> roller cam with roller lifters and rockers will gain about 40 hp from
> reduced friction.
It woudl have to be a very powerful engine to gain 40 hp...but
there is some benefit, after all even lowly Chevy truck engines
are full roller these days...
Jim
Ted Spradley
>
> Is there an advantage to an overhead cam of reduced friction like roller
> rockers and roller cams are to pushrod cams? My understanding is that a
> roller cam with roller lifters and rockers will gain about 40 hp from
> reduced friction.
I have no idea what sort of magic they use to reduce friction, but the
BMW V10 turned 19,000 RPM at Monza a few days ago.
http://www.formula1.com/news/headlines02/09/s10590.html
One of 'em blew up in four laps, though. Anyone have any URLs for
technical info on these F1 engines? Always lots of gossip about the
drivers, but it's hard to find even pictures of the engines.
Talladega Greg
there are definite benefits to overhead cam engines.
No pushrod means no deflection-better & more precise valve control.
Less mass in the valvetrain, better control & less "stacking" of variance,
(better control once again).
With double overhead cam you can get even more precise control,
and you can advance or retard either cam, or both.
Overhead cam is also able to vary valve action (Honda's VTEC is an
example of variable valve timing), and the Auto makers are getting real
Good, we'll see pneumatic valve activation (a.k.a. F1 engines, which are
now getting into the 19,000 rpm range! Normally aspirated! Exotic &
expensive).
That needs no valve springs, less propensity to break & ability to vary the
valve timing according to load, throttle position, rpm etc!
Talladega Greg (hopefully this made sense, is accurate & helped)
"Eugene Blanchard" <blan...@therockies.com> wrote in message
news:3D87F1AB...@therockies.com...
Talladega Greg
those F1 guys guard their engines (and everything else!) With passion!
I'd be surprised if there was accurate information on the latest iteration
of
that BMW V10, I haven't seen a picture of one (and I generally watch the
F1 races, and every other type of Racing on 4 wheels, Drag boats, some
Motorcycle-basically anything automotive or Racing related I'm there!),
And don't expect to! Sure would be nice to have a few pictures & maybe
a cutaway drawing or picture! 19,000 rpm! Jesus!! 316.66 Revolutions
PER SECOND! that's exotic!
on a vaguely related topic, did anyone watch the IRL this year?
The IRL races in the last few weeks were totally incredible! Margin of
victory at Chicago was .0024 secs.! 9.2 inches at around 200 mph,
Texas was .0096 secs. I believe, at around 225 mph-219 lap average!
Truly incredible Racing, the last 25-30 laps side by side, 4 or 5 deep!
At Chicago, with around 5 laps to go the difference between first & 9 or 10
was .9 secs. ! now that's close Racing!
/end off topic dissertation
Talladega Greg
"Ted Spradley" <tsp...@spradley.org> wrote in message
news:3D89D8E0...@spradley.org...
Talladega Greg
On a Big Block Ford!
In Rufus the Wonder Truck! (My wheelchair van).
Talladega Greg (accepting donations for major Overhaul!)
"lifespeed" <life_...@yahoo.com> wrote in message
news:2c507ad7.0209...@posting.google.com...
J Forbes
>
> Eugene,
> there are definite benefits to overhead cam engines.
> No pushrod means no deflection-better & more precise valve control.
> Less mass in the valvetrain, better control & less "stacking" of variance,
> (better control once again).
> With double overhead cam you can get even more precise control,
> and you can advance or retard either cam, or both.
> Overhead cam is also able to vary valve action (Honda's VTEC is an
> example of variable valve timing), and the Auto makers are getting real
> Good, we'll see pneumatic valve activation (a.k.a. F1 engines, which are
> now getting into the 19,000 rpm range! Normally aspirated! Exotic &
> expensive).
> That needs no valve springs, less propensity to break & ability to vary the
> valve timing according to load, throttle position, rpm etc!
>
> Talladega Greg (hopefully this made sense, is accurate & helped)
Sort of...but also more relevant to racing cars than street
driven rods....where big inches and low rpm and gobs of torque
is still more pleasnt to drive, imho.
Jim
Eugene Blanchard
across an ad for a variable cam timing gear called Varicam. From the
description and picture it looked like it allowed the cam timing gear to
rotate about 10-20 deg as the engine revved up. A strong spring kept it
from rotating a low rpm. The write-up said that as the rpm climbed, the
cam timing would retard. So a hot cam would act like a mild cam at low
rpm and "open" up at high rpm. It was even patented... Interesting to
see how the patent is described versus Honda's VTEC design.
--
Eugene Blanchard
The simplest thing I ever saw for this cam timing thing was a Varicam
mfgd. in
the 60's it was patented, but the company failed I heard...
it was a large pair of springs on an adjustable tension arrangement and
an
adjustable travel arrangement....just screw down the springs to delay
retard
and set the amount of advance retard where you wanted it....all located
on the
cam gear....simple as hell...don't know why company failed....they
worked well
in cars that had them.....in dragracing...GENE
Raymond C Drouillard wrote:
>
> On Mon, 29 Jun 1998 11:42:40 -0700 Sandy <sg...@wgn.net> writes:
> >Saw the idea in the 60's hot rod mags where some gizmo was attached to
> the
> >timing gear of the cam and it did some magical adjustmet by letting the
> >assembly slip and slide to alter the cam timing. Never saw one in action
> or
> >knew if they really worked, the idea was good.
> >
> >Sandy
Talladega Greg
Checkout the website.
They are expensive as Hell, but if you're building a street thumper,
well worth the effort, less valve spring tension, cam lift & more
airflow. Milder camshaft makes better power.
(On the aforementioned heads).
Checkout the website Jim.
Talladega Greg
Talladega Greg
Duh!
Talladega Greg
"Talladega Greg" <gsadki...@erols.com> wrote in message
news:amhnsc$gjj$1...@bob.news.rcn.net...
J Forbes
Notice that the high zoot heads start working at 4000
rpm...that's about when I like to shift.
A blower adds gobs of torque at low rpm, which makes for a lot
of fun driving with mild gears and an automatic tranny. And one
big claim of the Arao heads is they the will let you rev to 9000
rpm without valve float. Great for race cars, but not quite
what I want in my auto tranny street car, which is usually
running between 1500-4500 rpm.
I can understand why we don't see the Arao heads on any cars....
Jim
Talladega Greg
The Dyno charts go to 6000 rpm on the SB Chevy.
They are "capable" of 9000 rpm without exotic valvetrain stuff.
Point is they can flow more, with less radical cams & less expensive
valvetrain stuff.
If the idea didn't work, then Honda, Ford & everybody else wouldn't
be using 4 valve per cylinder heads.
If you can make better power, with less valvetrain work & rev a touch
higher, then gear accordingly-if it's even necessary.
They are for retrofitting 2 valve heads,
price is why they're not on more street cars.
Talladega Greg (forgot where I was going?)
J Forbes
>
> huh?
> The Dyno charts go to 6000 rpm on the SB Chevy.
> They are "capable" of 9000 rpm without exotic valvetrain stuff.
> Point is they can flow more, with less radical cams & less expensive
> valvetrain stuff.
buck heads until you get to around 4000 rpm. And I don't get
off on buzzing the piss out of an engine just to go kind of
fast. (hint-I don't like 5 speed trannys...or even 3 or 4 speed
trannys)
> If the idea didn't work, then Honda, Ford & everybody else wouldn't
> be using 4 valve per cylinder heads.
Chevy uses 4 valve heads...in their Indy car motors, but not in
anything else. Wonder why?
> If you can make better power, with less valvetrain work & rev a touch
> higher, then gear accordingly-if it's even necessary.
Not me....I'd rather have 700 ftlbs torque from 2000-5000 rpm,
than 500 ftlbs from 4000-8000. It's nice to be able to push the
pedal halfway down at 2500 rpm and 75 mph and have the car just
take off...without even downshifting.
> They are for retrofitting 2 valve heads,
> price is why they're not on more street cars.
Possibly...because you can get more hp/$$ by other methods.
Also, I wonder how you'd fit them into some of the tighter
engine bays? Looks like trouble!
> Talladega Greg (forgot where I was going?)
you too? :)
Jim
lifespeed
> Eugene,
> there are definite benefits to overhead cam engines.
> No pushrod means no deflection-better & more precise valve control.
> Less mass in the valvetrain, better control & less "stacking" of variance,
> (better control once again).
<SNIP>
Hey guys,
The Arao heads DO NOT have overhead cams. A serious shortcoming. The
benefits of 4 valve per cylinder are real, and do not require revving
an engine to ridiculous RPM. A 4 valve head actually flows more at
lower RPM than 2 valve heads, without destroying velocity. 4V heads
rev higher with a given camshaft duration, also.
4V heads are great for both torque and high RPM. The only snag in the
Arao example is that the problem of a pushrod valvetrain has been
aggravated by operating two valvesprings off one lifter. This
mechanical aspect isn't an improvement, although the flow certainly
is. Go check what the combined valvespring pressure is, on the Arao
website.
Hell, if I could have purchased 4V DOHC heads for my BBC, I would have
done it in a heartbeat. Given practical realities, and an expectation
of valvetrain longevity, I "settled" for Brodix B2+ heads.
- Lifespeed
Talladega Greg
Got caught up in the 4 valves per cylinder syndrome &
forgot the original poster's OHC-DOHC request.
Agreed on the valve spring & other issues,
not having to rev the piss out of them works wonders.
Talladega Greg (there's a market for OHC & DOHC heads
for the "dinosaur" V8's!)
"lifespeed" <life_...@yahoo.com> wrote in message
news:2c507ad7.02092...@posting.google.com...
Talladega Greg
Talladega Greg
"J Forbes" <jfor...@yahoo.com> wrote in message
news:3D8EBDD7...@yahoo.com...
Talladega Greg
torque "curve" is virtually flat! Unbelievably so!
http://www.araoengineering.com/dnochrts/dyno_sheets.htm
Talladega Greg (a nice Big Block w/4 valve heads for
Rufus the Wonder Truck! Donations anyone?)
"J Forbes" <jfor...@yahoo.com> wrote in message
news:3D8EBDD7...@yahoo.com...
J Forbes
>
> "Talladega Greg" <gsadki...@erols.com> wrote in message news:<amctrd$bvm$1...@bob.news.rcn.net>...
> > Eugene,
> > there are definite benefits to overhead cam engines.
> > No pushrod means no deflection-better & more precise valve control.
> > Less mass in the valvetrain, better control & less "stacking" of variance,
> > (better control once again).
>
> <SNIP>
>
> Hey guys,
>
> The Arao heads DO NOT have overhead cams. A serious shortcoming. The
> benefits of 4 valve per cylinder are real, and do not require revving
> an engine to ridiculous RPM. A 4 valve head actually flows more at
> lower RPM than 2 valve heads, without destroying velocity. 4V heads
> rev higher with a given camshaft duration, also.
Sure...but do you actually *need* more flow at lower rpm? The
whole reason to make heads flow better, is to be able to get
torque at high rpm. In street driving use, at least for someone
like me who isn't into 4.88 gears and 4500 stall converters or 6
speed rowboat trannys, high rpm performance just isn't something
I want. I want lots of low to midrange grunt...and I can get it
just fine with 2 valves/cyl and one cam in the block.
> 4V heads are great for both torque and high RPM. The only snag in the
> Arao example is that the problem of a pushrod valvetrain has been
> aggravated by operating two valvesprings off one lifter. This
> mechanical aspect isn't an improvement, although the flow certainly
> is. Go check what the combined valvespring pressure is, on the Arao
> website.
>
> Hell, if I could have purchased 4V DOHC heads for my BBC, I would have
> done it in a heartbeat. Given practical realities, and an expectation
> of valvetrain longevity, I "settled" for Brodix B2+ heads.
>
> - Lifespeed
The Arao heads might actually *fit* in a boat...I wonder how one
would squeeze them into a 55 Chevy with a big block? aside from
cutting off the front of the frame and starting over again with
a different suspension.
But yeah, they are neat heads....
Jim
Bob Raby
>whole reason to make heads flow better, is to be able to get
>torque at high rpm. In street driving use, at least for someone
>like me who isn't into 4.88 gears and 4500 stall converters or 6
>speed rowboat trannys, high rpm performance just isn't something
>I want. I want lots of low to midrange grunt...and I can get it
>just fine with 2 valves/cyl and one cam in the block.
>
midrange rpm airflow. That's what velocity is all about. That's why you need
better cylinder filling at low rpm. I think there is a misunderstanding of
terminology here. I think what Lifespeed was saying is that these heads flow
better without destroying velocity. That means they work better at low rpm.
Many heads with great flow numbers have terrible velocity and that is what
kills low end power. According to the dyno charts for these engines, they do
seem to work pretty good across the range, although I have my doubts about what
they included and left out of the engine and test descriptions. That flat
torque curve is a signature of a good street head. When we work heads, that's
exactly what we shoot for in most cases. This is not to say you can't
accomplish the same thing with a two valve, though in my experience, a two
valve won't keep working as the rpms climb like the 4 valve will unless it's an
extraordinary design. In other words, a two valve doesn't seem to have as big
a power band in most cases. A two valve big block with a blower is *plenty*
enough for most people, myself included. The power band of most two valves is
quite sufficient for most applications. If I had an unlimited budget, I'd
consider a 4 valve, but I'd make it ohc.
Bob Raby
"Bigger,Better,Faster,More!"
Remove nospam to email
lifespeed
> Sure...but do you actually *need* more flow at lower rpm? The
> whole reason to make heads flow better, is to be able to get
> torque at high rpm. In street driving use, at least for someone
> like me who isn't into 4.88 gears and 4500 stall converters or 6
> speed rowboat trannys, high rpm performance just isn't something
> I want. I want lots of low to midrange grunt...and I can get it
> just fine with 2 valves/cyl and one cam in the block.
What you need most is higher air velocity at low engine speeds. The 4V
heads provide high flow like a large 2V head, but without the 2V heads
drop in port velocity. They give you better torque at both low and
high speeds.
Quite the opposite of the high stall low gear ratio scenario.
> > 4V heads are great for both torque and high RPM. The only snag in the
> > Arao example is that the problem of a pushrod valvetrain has been
> > aggravated by operating two valvesprings off one lifter. This
> > mechanical aspect isn't an improvement, although the flow certainly
> > is. Go check what the combined valvespring pressure is, on the Arao
> > website.
> The Arao heads might actually *fit* in a boat...I wonder how one
> would squeeze them into a 55 Chevy with a big block? aside from
> cutting off the front of the frame and starting over again with
> a different suspension.
Size is always an issue, especially with OHC. That darn 4.6L Ford is
physically larger than a BBC!
- Lifespeed
J Forbes
I'm not saying that the high buck 4 valve heads kill low rpm
torque, what I'm saying is that you can get plenty of low rpm
torque with low buck 2 valve heads....and if you don't want to
run high rpm, then the extra $$$ for the 4 valve heads is a
waste.
Hence, I'm not interested in buying Arao heads.
I think we are in agreement :)
Jim
J Forbes
>
> J Forbes <jfor...@yahoo.com> wrote in message news:<3D90C4B7...@yahoo.com>...
> > Sure...but do you actually *need* more flow at lower rpm? The
> > whole reason to make heads flow better, is to be able to get
> > torque at high rpm. In street driving use, at least for someone
> > like me who isn't into 4.88 gears and 4500 stall converters or 6
> > speed rowboat trannys, high rpm performance just isn't something
> > I want. I want lots of low to midrange grunt...and I can get it
> > just fine with 2 valves/cyl and one cam in the block.
>
> What you need most is higher air velocity at low engine speeds. The 4V
> heads provide high flow like a large 2V head, but without the 2V heads
> drop in port velocity. They give you better torque at both low and
> high speeds.
>
> Quite the opposite of the high stall low gear ratio scenario.
THe high stall/low gear thing is that you need a long duration
cam to make an engine work at high rpm (you also need heads that
flow at high rpm, of course). So, if you set up the car to work
at high rpm, then it won't be "driver friendly" at low
rpm...regardless of the heads it has.
And there are a lot of heads out there that work great at
low-mid rpm...with two valves.
> > > 4V heads are great for both torque and high RPM. The only snag in the
> > > Arao example is that the problem of a pushrod valvetrain has been
> > > aggravated by operating two valvesprings off one lifter. This
> > > mechanical aspect isn't an improvement, although the flow certainly
> > > is. Go check what the combined valvespring pressure is, on the Arao
> > > website.
>
> > The Arao heads might actually *fit* in a boat...I wonder how one
> > would squeeze them into a 55 Chevy with a big block? aside from
> > cutting off the front of the frame and starting over again with
> > a different suspension.
>
> Size is always an issue, especially with OHC. That darn 4.6L Ford is
> physically larger than a BBC!
Yeah, I've heard folks say they wanted to put one in an early
ford street rod but it was way too wide...
JIm
>
> - Lifespeed
lifespeed
> > Quite the opposite of the high stall low gear ratio scenario.
>
> THe high stall/low gear thing is that you need a long duration
> cam to make an engine work at high rpm (you also need heads that
> flow at high rpm, of course). So, if you set up the car to work
> at high rpm, then it won't be "driver friendly" at low
> rpm...regardless of the heads it has.
That's not entirely true. A 4V head flows more for a given camshaft
duration. They have a wider powerband as a result. Good low speed
torque from the higher port velocity, good high speed power because of
increased flow, even at low valve lift.
> And there are a lot of heads out there that work great at
> low-mid rpm...with two valves.
They just don't do as good a job at both ends of the powerband. There
are plenty of good 2V heads, but its hard to beat 4V.
- Lifespeed
Eugene Blanchard
low rpm? Then advance its timing at high rpm like the varicam theory
went?
--
KB
you can only do so much to alter a given grind but it sure would help
broaden out the torque curve. KB
--
Thunder Snake #9
Read the posting FAQ for AHPBBFM at
http://members.dancris.com/~cobrajet/AHPBBFMfaq.html
lifespeed
> Can you take a hot cam and retard its timing so that it performs well at
> low rpm? Then advance its timing at high rpm like the varicam theory
> went?
Advance is only one small aspect of cam timing. Lobe separation angle
and duration are also pretty significant.
Just off the top of my head, I would say changing the centerline angle
alone is not of much help.
- Lifespeed