RE: Intake question

["Earl H. " <earlh@xxxxxxxxxxxxxx>]

Paul,

Now you have done it. This can be a bottomless pit involving complex 
engine theory including CFM (computational fluid dynamics), cam theory, 
all revolving around the physical limits of the parts you have available and

the limit on your Visa. 

Remember, things change, and technology advances. Xram manifolds IMHO 
were quite an advancement by Chrysler, but like a lot of evolution became 
a dead branch in the tree of evolution. This technology has advanced to 
the level of sheet metal manifolds now used by Pro Stock motors. That is not

to say that the Xram manifold does not work, or is not cool, but in the 
realm of max performance, it has seen its days. Here in lies the rub. It
works 
well with parts of that era, but putting an Xram on a new set of Indy heads 
would not be the best overall application for that manifold.

My recommendation if you're going to build a motor, and you do not have 
the engineering back ground or experience of building thousands of motors 
over many year's (like Don) is to pick a proven combo that a know engine
builder has 
proven works and use it, if it is in alignment with your intended usage. 
Everyone gets in trouble when they try to out think the experts based on 
a magazine article they just read...

I happen, as you know to love RPM manifold's. Based on my past usage, they 
always have given me the best bang for the buck. Many recent articles have 
backed this opinion I developed up with dyno facts. Remember, the true
runner 
length is measured from the butterflies to the valve. We could get into raw
flow 
vs velocity and burn up a good night of bench racing. For a street motor, I
will 
take velocity over raw flow every time. This feed's into what I think you
want to 
know and what is causing you some issues. In theory you're correct regarding

dual plane vs single plane. But technology advances have narrowed that gap.
The 
RPM works almost as well as a Victor, and better when you take into
consideration 
the over all curve for a street motor. Just like head flow, it is not always
the raw 
flow that matters, but what is the flow rate under the curve that makes the
great 
combo. Many times less flow on top, but more flow under the curve makes the 
best motor.

Call Don and ask him to build you a motor. I know he claims to be retired,
but 
he just might be glad to help a guy out.

I have most likely put more mud in the water than you liked, but my point is

don't over think this thing. 

Earl




I read the "Crossram Chronicles" article that Gary added to the website. 
 It talks about a runner length of 15" being the magic number to 
scavenge the resonant pressure waves which result from the intake valve 
opening and closing.  And that this length was tuned to an engine rpm of 
5400. Giving the max wedge crossram manifold a distinct advantage over 
the earlier long ram  manifold which was tuned to provide more torque 
and power from rpm's in the low 2000's to @ 4800.

In reading general theory about intake manifolds it is stated that a 
single plane manifold generally works better at higher rpm than a dual 
plane which will give you more torque at lower rpm & better idle 
quality.  Since a dual plane has longer runners this would seem to put 
these two theories at odds with each other.  

I don't think any of the commonly available street type intakes have 
runner lengths anywhere near 15".  I'm thinking about The Holley Street 
Dominator and the Edelbrock Performer RPM in particular.  But since the 
Performer is a dual plane it should have the longer runners, making it a 
better intake for low end torque and the Street Dominator a better top 
end unit.  I am in the process of making some performance modifications 
to my 440 so I'm trying to understand this a little better.

Can anyone clear this up for me, Earl, Don, anyone?

Paul L.
'63 Sport Fury
440/727
http://www.1962to1965mopar.ornocar.org/ml-lennemann63.html


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Please address private mail -- mail of interest to only one person -- directly to that person.  I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic.  Thanks!

'62 to '65 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html.