Attn Don - compression

[Earl Helm <earlh@xxxxxxxxxxxxxx>]

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Don,

I am putting a low compression 72 440 in a truck. I called up Jim
and had him grind me an advanced cam, about 5 degrees. I am
anxious to see how it works. All I want is low end power for
towing. You know Jim, he has an answer for everything. 

Earl


"I put in a 509 cam and now the compression is 130"
Give the man a cigar!
You are a very observant fellow. Why did that happen? Because the valves
with the new cam are open longer . No compression takes place until the
intake valve closes at the end of the induction stroke. Actually it is
held open into the early part of the compression stroke as the air/ fuel
mixture is flowing into the cylinder at a high rate and does't want to
stop (Intertia) So we can hold the valve open there for a tiny bit as
the flow coming in is strong enough that the slight upward movement of
the piston doesn't upset the flow. Eventually it does and we close the
valve just before that point . Unfortunately we lost a few pound per
square inch of compression while we were waiting for the intake flow to
slow up. 
What do we do now? Can we get that back? YES. That is why we raise the
compression when we lengthen the camshaft intake duration. The two are
inseperable and this is the key to making horsepower. We don't raise
compression to get more compression (after we reach about 10 to 1) we
raise it to get back what we lost from holding the intake valve open
longer. 
Once you understand this the rest is a piece of cake. 
There is a book which is more of an engineering type book than an fun to
read book called Design and Tuning of Competition Engines. It is by
Philip H Smith and I believe it was written across the pond (aka
England) It is a very very good book and if you can stand that type of
intensive reading and study will help you understand many of the things
that go on in the engine. It has few photos and those that are are
engines we would have little interest in but it is good solid engine
sceince unlike much of the Bullschlage that we are often subjected to
from our magazine articles. 
Actualy compression can tell you a lot more than one would think. It
could take about 4 or 5 pages to cover the subject but i am impressed
with your direction of thought! NEVER stop being curious. Don 


[Non-text portions of this message have been removed]

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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. 

===========================================================
Are you looking for savings on products you use everyday? 
Visit Quality Health today and see the coupons, free 
samples and special offers our members enjoy each and 
everyday.
caab3ozb7yoMzf/ Ivo Interactive
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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. 



b7yoMz.