[Shotimes] (OT) Marauder

[Donald Mallinson]

Well, a 4V design has more to do with high rpm breathing 
than emissions.  IT is easy to get plenty of swirl in a 2 
valve design, and has been proven, there is no real 
emissions bonus between the two designs.  Several 
manufacturers have plenty of OHV designs that meet or exceed 
emissions for the forseeable future.

Many people forget that OHC or 4Valve designs are not 
anything new, they are just the "thing" at the moment. 
There are also several examples of 4V pushrod single cam 
motors!  The OHC design came along at almost the exact same 
time as the ion-block pushrod did, I can't say exactly why 
the pushrod won out many years ago and became the dominant 
design,(probably because of cost,but when it comes to the 
world of todays motors, not much is new other than computer 
control, pretty much everything else was thought of and 
tried in the first half of the 20th century.  Chevy made a 
V8 OHC motor many years ago, long before the small block, 
about the same time as the flathead Ford.  It was dropped.

What WILL be dropped in the near future will be ALL cams, 
OHV or OHC. I won't be upset at that moment, and I hope you 
won't be either when those to cams per head become junk heap 
fodder.  Individual control of each valve lift/duration/open 
and closing velocity is the next big thing.  Already 
happening in F1, it will happen in big diesel engines next 
because they run slower and a beginning design for an 
actuator will work.  Higher reving gas motors will come 
later, but it will come.

The hydraulic VS solid lifter is a non issue for this 
discussion since it can be done either way no matter what 
design, I never talked about maintenance since the 60k is 
really not needed till 100k, that is what experience has 
taught us.  I don't see a real difference on maintenance, 
but experience has taught us that 4V motors are MUCH more 
expensive to re-build.  Twice the valves and machine/parts 
time on the heads is the main difference, and one cam versus 
four.

As far as what wins on power?  4V motors sure don't have an 
edge there.  Ford is resorting to blowers to come close to 
the small block that is running more power, more torque and 
the same if not better mileage or emissions.  End game on 
that discussion.  If the 4V motor had such a big advantage 
as you imply, then there would be big HP motors out there 
without power adders.  Check out any fast import racer, 
virtually ALL of them rely on power adders to get numbers. 
   They don't have the low end torque to get good et's so 
they rely on top end power for MPH and help on ET.

I admire and love the 4V motor in my SHO's.  I also admire 
and have owned and enjoyed the pushrod motors.  My 66 Grand 
Prix has a smooth power that can't be duplicated in a 4V 
motor, or at least it hasn't been yet.  My SHO has a top end 
rush that isn't present in OHV cars other than extreme race 
cars.  I like both designs because they BOTH have their 
postive and negative points.

I have spent this much time on this discussion, just because 
you claim such a huge advantage for the OHC 4V design.  Yes 
it does have some breathing advantages if you want to run 
high rpm applications.  For 99.9% of the driving that 
Americans do, the OHV 2V design, that is just as old as the 
4V OHC designs, is a BETTER application, this just can't be 
disputed.  More torque down low, same basic economy/emissions.

This is getting old, and has the makings of an argument 
between two people that won't change their minds.  I choose 
to go with the evidence that we know about and experience 
that teaches us that while one design is "considered" newer, 
it isn't, and there are uses for each.

People will be hot rodding small block Chevy's till cars are 
finally outlawed and we all use Star Trek transporters.  AND 
people will probably be making fast 4V OHC designs too.  But 
the OHV 2V people will have more money in their pockets and 
easier speed on the drag strip!

Beam me up Scotty!

Don Mallinson

David P wrote:

> Since all OHV motors are two-valvers, and four valves allow more efficient
> combustions, then pushrods DO have a bit to do with emissions, at least
> until they figure out a way to cram 4V onto a single cam. Sure, injector
> placement, intake flow, etc play a large part, but when considering solely
> 2V vs. 4V, 4V is going to win on emissions and power. You think maybe there
> is another reason why the Corvette runs a 2.73 final?
> 
> As for OHC being high maintenance, I think you are forgetting that the SHO
> does not have a hydraulic tappet. Remove the hydraulic tappet from any OHV
> motor and it becomes just as maintenance intense. Not as expensive to build,
> but just as expensive to maintain. If Yamaha had inserted hydraulic tappets
> into their design, we would not be sitting here exclaiming the need to do
> the 60k on time.
> 
> Sure, the small block (or more specifically, the OHV design) will be around
> for some time, but eventually it will be dropped in lieu of more efficient
> designs in our nation's quest for emissions reduction. Don't get upset about
> it though, as OHC's days are numbered as well. There are much better
> air/fuel injections systems on the boards and in testing that don't have
> valves as we conceive them that will see fruition in the last half of this
> century, leaving OHV as the predominant valve design of the 19th, 20th and
> 21st centuries. Not too bad a run, but definitely a technology that has
> outlived it's usefulness.
> 
> 
> David P
> 
> 95MTX