Re: Cams
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Re: Cams

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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 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:
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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:
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