Re: Cams

[moparbikeguy@xxxxxxxxxxxx]

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I had Racer Brown grind the cam for my stroker and couldn't be happier. 
I will never use anyone else.

'65 Coronet 500
500 CID Wedge

-----Original Message-----
From: Darwin <65Val@xxxxxxxxx>
To: Don Dulmage <big-d@xxxxxxxxxxxx>
Cc: 1962to1965mopars@xxxxxxxxxx
Sent: Sat, 3 Dec 2005 20:45:24 -0800
Subject: Re: Cams

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""Sorry to go on so long""

 Don,dont EVER say that. I love your emails as feel I'm getting a great 
education and insight into building high performance motors from 
someone who's really "been there,done that". I've saved almost all your 
messages in a special folder and refer to it if I ever need the info. I 
thank you very much for your knowledge and your willingness to share it 
with us.

Darwin/Victoria BC/Canada
'65 Cdn.Val.Cust.100 'vert
Slant 6/factory 4 speed

----- Original Message ----- From: "Don Dulmage" <big-d@xxxxxxxxxxxx>
To: <1962to1965mopars@xxxxxxxxxx>
Sent: Saturday, December 03, 2005 5:22 PM
Subject: Cams

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 It is true i like Racer b s cams but only becase hey really really 
work. Putting all that aside here is what i found out in my years of 
playing and testing BB Mopars.

 Biggest problem is getting enough duration. We are conditioned to 
being overcautious because we are constantly reading Chevy stuff and we 
some how get ingrained in our mind that it applys to BB mopars too. But 
not necesarily.
 First if you are buying a cam you want a grind that is Mopar Specific 
meaning it has actually been designed and tested on a Mopar . Most cams 
are designed on a 350 chev and then transferred to everything else in 
manufacture.

 The Comp cam extreme energy series are specifically designed to take 
advantage of the Mopars large lifter diameter (904) so even though I 
prefer the Racer brown they are good cams for these engines.

 Secondly when you modify a set of IRON heads you discover that valve 
lifts over 540 (Dvorak says even 530) cause a reduction in flow. (You 
can port the head differently so this is not the case but the end flow 
figure will be no higher that when you do it properly so you have 
gained nothing. In other words if you can get 275 cfm 2@540 or 275 cfm 
@600 you still have only 275 cfm so other than spending more for valve 
springs for the extra lift you are in exactly the same place)
 So assuming you want the lift to be no more than 540 you need to 
decide on the duration. Every degree of duration produces a specific 
number of rpms. That is what duration does. It controls the engine 
speed available.
 Too much will kill torque and to lttle will limit engine speed. this 
is where it get tricky. To get a 440 to run strong to 6150 we need 
approx 253 deg at .050 duration in an hydraulic (About 268 in a solid 
cam)
 When we look for a cam with that much duration it is hard to find one 
with 540 lift or less. Racer brown had this figured out years ago but 
the rest are just catching on now. That is why we really like the 
ST-H-42. It is an absolutley BRUTAL cam that suits these engines really 
really well. (because it was designed for them) Sig Erson used to make 
a cam with 525 lift and 310 adv duration which was pretty close at the 
050 mark but when Mallory and them got in bed together they stopped 
making it. Both these cams require really good tuning skills but power 
is unbelievable.
Comp has been working lately in this same vien .
 So what about if I have too much diration I will loose torque thingy 
you ask?
 Well the BB mopar 440 has about the second highest stock torque rating 
of any of the engines. If you had any more you probably couldnt stick 
it to the ground anyway so it is a non-issue. Even with these big cams 
and more we were backing the cams off (retarding ) a few degrees to get 
rid of some of the monster toque we were generating. So bottom line is 
with this particular engine it is not a relevant issue. With a 383 or 
400 it would of course be much more important.
 When you go to Alum heads like Indys or Edddys the 540 lift limit goes 
away and you can run as big a number as you have guts and gold for 
(Pick your cam lift to match the cylinder head fow rating. See whare 
the highest point is (ie like peak flow at 650 lift would use an 
hydraulic cam of 650 lift (A solid would need more because its lift is 
given at .000: lash so it would need a cam with more lift minus the 
lash to arrive at the same figure.
 For instance a solid cam for a head with peak flow at 650 lift would 
need a cam with 678 lift - .028" valve lash = 650 lift. (Some cams are 
rated at 020 as well. Check the specs before you buy.
 This is the type of thing that no one ever tells us which is why I 
wrote the articles I did in the first place that turned into the book.
 We ran, in the course of a few years, some 23 cams. Racer Brown Cams 
matched the one cam exactly (but was much easier on the valve train so 
we still like it best) and beat all the rest. That is why i prefer his 
STX 20 for instance.
 How do you find out what duration you need? You start by keeping a log 
book of every cam you run and its peak power (often RPM trough the 
traps in a properly set up car.) You have to be honest as well. If you 
BS yourself your results are meaningless. After awhile you get a 
feeling for what the motor wants. I use 25.34 RPM for every deg @050 
myself for Hydraulic cams and 25.35 for Solids because they need extra 
ramps to accel and decel the valve lifter that a hydraulic does not 
need in the same fashion.
 This has worked very well for me and for others I have given it to. 
Even some Ford racers have used it with excellant results.
 Dont expect the cam guy on the phone to understand this . It comes 
about by lots of trial and error but never the less it works. 
Understanding how much lift you need and how much duration you require 
will get you to above average performance from seemily mundane parts in 
a big hurry.
The next secret is to match the cam to the compression ratio.
 No compression takes place until the intake valve closes at the early 
stage of the beginning of the compression stroke. That leaves less 
distance of piston travel or compression stroke to build pressure but 
the longer we hold the valve open at the bottom of the intake stroke 
and into the beginning of the compression stroke the more cylinder 
filling at higher RPM we have (to a point , everything has its limits. 
)The only way to get the cylinder pressure back where we want it is to 
use a piston of a higher compression ratio or reduce clyinder head 
combustion chamber volumes. That is why you can ran engine with 10 or 
even 10.5 compression ratio on the street on pump gas with a big cam.
 the 10 or 10.5 ratio is a strictly mechanical rating and assumes the 
valves are all closed at the BDC (bottom) of the intake stroke and the 
beginning of the compression stroke and that is how the ratio is 
determined. In fact especially with a prefiomance cam they are not and 
compression does not take place till the intake valve is fully colosed. 
By that time the piston is already moving up the bore , all be it 
slowly , so the distance of the ACTUAL or REAL compression stroke will 
be somewhat less than the 3.75 stroke (say only 3.70" for instance) 
that we would normaly use to caculate it. and cylinder pressure at the 
end of the compression stroke would be reduced.
 IE I once tested this for a local fellow. We took a stock 327 mouse 
and measured the compression. It was 135# on my gauge. We installed a 
350 Hp chevy grind in the motor and measured it again. It was now 
between 95 to 97 #. He would need to raise the compression by 30 to 35 
# to get it back where it should be. Because of a whole host of other 
factors too long to go into right now he would need to raise te ratio 
about 15 to 18 % . The factory by the way did this when they built the 
350 Hp engine. The subject is kinda complicated but not too bad of you 
just go one step at a time.
 Anyway. These are some of the major factors ueed for cam picking for 
max bang for your buck. (While i have not personally run one I have 
raced against cars with the Mopar 533 hydraulic grond and have come to 
believe it is also a very good cam.
 The vast majoriity though offered to us are just pure crap and were 
desgned and tested for a 350 mouse and nothin else.
 This stuff is much easier to explain with a blackboard and a few 
chairs that with a keyboard. Sorry to go on so long.
Don
Author of
Return to Deutschland (True Adventure)
Old Reliable (Mopar)
http://stores.ebay.ca/Don-Dulmage-Enterprises
[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 
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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!

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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!

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