RE: Cams

[Richard Kinsley <r.kinsley@xxxxxxxxxxxxxxxx>]

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. wrote:
> 
> ""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)
> ------------------------------------------------------------------

Ditto and then some.
> 
>
Rich Kinsley  '64 Polara 4 dr 318poly w/goodies

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