Demanding Modular Cam Specs

Discussion in '96-04 - 2V Specific' started by 96blak54, Jun 7, 2015.

  1. 96blak54

    96blak54 Legend

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    Lets take a look at modular cams and discuss why "old school" cams specs are almost useless. My intention here is to offer insite for those confused about cam specs.

    A modulars cam lobe is big....period. Much bigger than the old in block camshafts of yesterday. These newer over head cam engines are not as restricted with cam lobe size like a cam that needs to slip through 4 bearing races located in the center of the engine block like the small blocks do. Instead, the modulars drop directly into the head and caps hold the cams in place. This allows for a cam lobe to be bigger. And since the cam lobe directly controls the follower to the valve tip...no levers, push rods, or adjusters...* their is very minimal deflection of the components.
    Deflection is where the components will be in motion under stress and have a little bit of distortion that causes the component to move away from its nominal specs. For instance the inside block camshaft creating pressure on the roller(.0005), the roller presure to the adjuster(.0005), the adjuster to the pushrod(.020), the pushrod distorts and causes its length to be reduced(.001+), aluminum rocker lever distortion(.001+), rocker stud distortion(.003+) and the gray area of all the contact points being completely intact with no amount of play(.003). Im leaving out valve stem motion from spring inertia and rocker tips not controlling it... (.005?)
    Youll notice the amount of play with in the old school block setup.

    [​IMG]

    Modular left / old windsor right

    This is why "old school" cam specs are useless in modulars. Im refering to a cams duration @.050". Back in the olden days, this was a fair measure used for what I just explained.

    Remember the modulars have big cam lobes? Compared to the old camshafts in the block...they are bigger! Much bigger, also adding the direct connection to the valve tip, eliminating chance of play. That big lobe gives more length available to valve articulation. This means subtle soft openings as well as closings. It also means holding valves open during overlap were the piston is the closest at the top(a pi head has .060" valve lift to head deck surface) You can see how the modular camshaft can hang a valve open for a good amount of duration under .050". Any builder will look at the .050" duration and crunch it with the actual seat open/close duration (normally given at .005" lift per adjuster type) to get an idea of lobe lift ramp rate.....only if the manufacturer issues the seat open/close specs.

    Seat open/close specs known as advertised duration is just that.....actual(or close to) cam duration from the cams base circle. Base circle is the low point of the lobe(imaginary circle) when the valve is shut, but when the lobe moves from that circle(valve lift)duration starts.

    Compression starts directly when the intake valve seats!(close)..period. Not .050". 70% of your exhaust exits directly when the exhaust valve cracks open. This actually is the BANG you hear(thousands of hot psi ready to leave). Overlap begins when the intake valve raises dirctly off the seat..... while the piston nears the top...... when exhaust valve starting to shut.... and this leads to overlap ending when exhaust valve seats ....shortly after the piston starts to desend......90% of this happens under .050" with a modular camshaft. Old school engines could NOT achieve this respectfully. SOOOOO..... why only issue .050" durations for a modular cam... when the seat to seat specs are the most critical. These mod camshafts are not like the old ones where valve articulation was minimum. If the manufacturer will not issue seat to seat specs (Advertised duration) ...choose a manufacturer that will!
     
  2. 96blak54

    96blak54 Legend

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    If I were to spend $600 for new camshafts, I'd better darn know every tech spec of my $600! While one cam company offers hype for $600, the other offers actual specs/ engine build potential!

    Hype = Unknowing

    Knowing = knowledge

    If you never consider building a modular engine and otherwise just want cams, get the hype.

    If you make an investment into this hobby, get the knowledge!
     
  3. Wichers123

    Wichers123 Well-Known Member

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    But what I find with mod motors vs pushrods is that our mods can't swing no more than .575 lift. .600 lift would need a complete custom piston to be able to work. As on push rod they are using .600-.650 lift gaining that much more power over mods. The idea is valve placement and angle to piston. The push rods use a valve location that is flat to the face of the piston where mod uses and high angle with shrouding to piston. I'll still take mod over Dino pushrods anyday.
     
  4. 96blak54

    96blak54 Legend

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    Good info, but didnt you know the revised heads come with all the advanced features you just described.

    Trickflow....lol
     
  5. Wichers123

    Wichers123 Well-Known Member

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    Yeah but at 2500 for heads all machine work and off the shelf cam profiles I'd like to use that money somewhere else and deal with shit valve lift.
     
  6. 96blak54

    96blak54 Legend

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    $2500 is steep!

    The pi heads ports stall at .550 lift, so really no need for any more, but thats the beauty of the ports design. The port flows like no other at low valve lift. The valve spends more time under .300lift, soo if you can maximize flow potential at low lifts, all the areas I descibed in the first post get maximized. A tall lift cam plays very well with npi heads because of its port design.
     
  7. 96blak54

    96blak54 Legend

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    Adding more info here and this has nothing to do with Fords. The chevy ls series engines, being an in block camshaft engine, also increased the cam journal dimensions to accommodate a bigger cam lobe. The cam lobe size is restricted to the blocks bearing hole size. Increase bearing hole I.D. allows for increased cam lobe radius. Old school 350chevy cam journal size is something like 1.900". Now the Ls family was increased to (possible more, im not a chevy guy) 2.300"-ish tops. This is really good for power potential as it allows lots of cam lobe radius to articulate the valve under .050". In other words, cracking a valve open for a good length of degrees and not suddenly opening or shutting like a tiny journal would. Again, knowing actual open and closing points of the valves gives insight to potential build.

    Take for instance the npi cam. This same camshaft valve opening/closing points but for a 302 in block cam would be a snotty cam just because of the rampant valve opening closing points of a tiny lobes.

    Driven by a tiny bore and more stroke than a 514cuin
     
  8. lwarrior1016

    lwarrior1016 Moderator Staff SN95 Supporter

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    Always good info coming out of ^this guy! Thanks for the education.
     
  9. 96blak54

    96blak54 Legend

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    Welcome! All inspiration from the folks at SN95forums

    Driven by a tiny bore and more stroke than a 514cuin
     
  10. PinkieT

    PinkieT Well-Known Member

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    I bought an Xtreme High Lift Comp cam for my old school 440 for $175. It has 16 lobes. Two cams with eight lobes each for my 4.6 2V is at least $600, same vendor. Can somebody please explain why the 4.6 cams don't cost $350, twice what the 440 cam cost?????
     
  11. 96blak54

    96blak54 Legend

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    Exactly! Cause your old school engine is not new technology. ...even though....the same process for machining. Actually, machining out a modular cam is cheaper because it starts from raw material instead of a casted form like the old school stuff