cam suggestions

Discussion in 'Street/strip 400/430/455' started by ramzee1, Jan 12, 2018 at 2:53 PM.

  1. ramzee1

    ramzee1 Active Member

    right now I'm running a 455 with ta212.....looking for something with a little more lope...i have stock rocker arms with non adjustable push rods..stock rocker shaft....i don't nothing 2crazy
     

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  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    The next cam up from the 212 is the TA284-88H. If you go bigger on the cam, you may need more static compression. It is very possible to change the cam in an engine, to one that sounds better at idle, and actually make the car slower. Also, you need adjust ability in the valve train. The only alternative to that is to measure for correct push rod length and then order the correct ones.
     
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  3. ramzee1

    ramzee1 Active Member

    make it slower why so?...guess i might as well keep what i have
     
  4. 300sbb_overkill

    300sbb_overkill Well-Known Member

    Because you need to match your static compression ratio with what cam you chose or you could end up with a dog that eats WAY to much. GL
     
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  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Because of a term called Dynamic Compression. Read up.

    http://www.empirenet.com/pkelley2/DynamicCR.html

    As you go bigger on the cam, the intake valve closes later. When choosing a cam, you need to take everything into consideration. Your static compression ratio, gearing, power brakes or not. What do you expect from the car? It isn't as simple as stuff in a bigger cam, you get more power.
     
  6. ramzee1

    ramzee1 Active Member

    thanks....im just going 2 keep what i have...lol
     
  7. alvareracing

    alvareracing Well-Known Member

    Larry is correct but I think he didn't quite explained for you to understand. You have to understand what is happening to the squeeze as the piston is coming up. Like he said, normally the bigger cam keeps the intake valve open longer, the squeeze of air and fuel is going right out (lost of compression)and there is a lot less power to drive that piston back down, in few words. That is why when doing this is real important to plot the cam and record every crank degree so you can see where the piston is in relation to the valves. That is why more static is recommended. The whole understanding of how it works is not as simple as people think, and why it takes sooooo long to build one right. It can sometimes over whelm people when you get deep into it. You can use your ta212 as a mock up and see where you can improve on the profile. That is another reason to have a cam ground instead of buying off the shelf. You can zero in exactly at what degree to close the intake and open and close the exhaust. You will spend days and days just plotting cams and getting the dynamic where you want. On my new motor we only focused on dynamic and didn't even worry about the static, what ever it came out to be that was it. I hope I didn't ruin your idea but the more you know the MORE you have to know!
     
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  8. ramzee1

    ramzee1 Active Member

    actually I'm glad you broke the **** down like this thanks!!!!
     
  9. Bens99gtp

    Bens99gtp Well-Known Member

    As refered to, it all has the do with the squeeze. If you have a 9 to 1 motor and but too much duration in it you could end up only having let's say 125psi cranking compression, but the same motor with a smaller cam might go 170ish. The high stain compression is used with cams with a lot of duration to get the cliner pressure up. Just like to small of cam on a motor with 14 to 1 might create too much pressure.

    It would be wise to measure your cranking psi now to know where you are.

    This is one of the things a supercharger does, not only more air more fuel, but more cylinder pressure.

    To much cylinder pressure will cause fuel to auto ignite, hince why with more compression normally leads to higher octane to resist this auto ignition

    I randomly picked the 125/170 out of the air just as a reference.

    My race motor sees over 215psi, my stk 3.4 in my minivan see 185, my low compression 454 in my boat only goes 150,
     
  10. 8ad-f85

    8ad-f85 Well-Known Member

    If you are going to go through the work involved in a cam swap, do a little bit of head work and make your gain worthwhile.
    If your heads flow just a little bit better, it can make use of a slightly more aggressive cam without losing bottom end.

    'Typically speaking'............. a cam with slightly more overlap but with similar durations and having an LSA with a lower number (TA212 112* vs. 108*) will BOTH idle choppier AND have more snap or response right off idle and through all but the very top end of the powerband. The 108* or lesser nummber being the more aggressive cam.
    Also generally speaking, tighter overlap cams this small don't make the idle intolerable, just a bit more noticeable.
    What's supposed to happen is that while idling, and the extra overlap is worsening the idle...the engine will benefit from that overlap to wake up the engine sharply just above idle.

    The danger of higher overlap and longer cam durations is that the wake up point on the cam could be at a high enough rpm to be a rough idling turd that sounds mean and never wakes up.
    The stock 350's will then run right by you, even with the 2bbl and the Dynaflow trans :D :D :D JK!
     
  11. 8ad-f85

    8ad-f85 Well-Known Member

    You don't see many useful dyno comparisons of this because the industry standard water brake dynos cannot hold a big beast like a 455 very well (if at all) at low enough rpms for a relevant comparison, such as near the converter flash rpm or lower. Were talking below 3000 rpms here.

    Also, the benefits of long tube headers by themselves or in conjunction with higher overlap cams with cams this tame are similarly not seen real well if compared using the aforementioned water brake dyno.

    Talking non-brand specific here now...similar sized engines 'can' see an 80-100 lb torque increase AT those lower rpms, before the two different cams begin to run a closer torque curve to each other.
    This Might not be verifiable at a drag strip where the engine spends more time running well above that rpm range, but will noticeably rip your head off on the street IF you can keep the tires from blowing off the pavement.
     
  12. gsgtx

    gsgtx Silver Level contributor

    i could never understand why someone would want a cam with more lope or says i want a cam with a rougher idle. WHY. i guess am different, i want a cam with the smoothest idle i can get and still makes my car go faster.
     
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  13. 8ad-f85

    8ad-f85 Well-Known Member

    The idle can see significant improvements with different carbs and head characteristics.
    It isn't exclusively 'the cam' or it's relationship to dynamic compression.
     
  14. RG67BEAST

    RG67BEAST Well-Known Member

    Without any engine specs. (comp. ratio, head work and or flow, exhaust, etc.) and the converter stall and rear gear it would be hard to recommend any cam. All the posts are very informative to say the least. If just basically stock I'd stick with the 212.
    Ray
     
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  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Because that lope is a sign of increased overlap, and overlap helps cylinder scavenging at higher RPM. More duration lets the engine breathe at higher RPM where it can make more power, but as you increase duration, you increase overlap, and the rough idle. That is why cylinder head flow is so important and why anyone wanting more power with less downsides should start with good head flow. Great flowing heads let you use less cam so you get the power with more street ability.
     
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  16. gsgtx

    gsgtx Silver Level contributor

    lope is not always a sign of power. a wider LSA gives you less lope, a higher advertise duration compared to a low duration @.050 gives you more lope, a low advertise duration with more duration @.050 would have less lope. so would a tight LSA cam with lots of advertise duration and little duration @.050 with a rough idle make your car faster ? maybe, maybe not.
     
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Agreed, but my point is that some think lope = more power, probably because a bigger cam usually produces a rougher idle. Maybe, but not always. The OP definitely thought so. Now he knows there is more to it than that.:)
     
    Last edited: Jan 13, 2018 at 10:15 AM
  18. gsgtx

    gsgtx Silver Level contributor

    i guess when you ask what cam they are 3 ways to go. want a cam with the rough idle and dont care about power. want a cam with the most power with a smoothest possible idle. or want a cam with the most power and idle is not a factor.
     
  19. 8ad-f85

    8ad-f85 Well-Known Member

    For clarity...

    It helps it wherever the cam wakes up the powerband, not just high rpm.
    Higher overlap cams having short durations wake up right off idle, and sharply.
    They do not always idle roughly with such small specs.

    Again, the cam is not the sole determiner of idle quality.
    This thread is discussing fairly tame spec'ed cams in a large engine.
    The idle won't change that much.
    Besides...with a non-stock cam, the OP is going to use a different initial timing setting and doesn't have to use the same idle speed spec as stock.
    That +150 rpm with a few more degrees timing is going to idle pretty good yet.
     
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  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I think I have the best compromise. My engine easily idles at 750 in gear, a little rough, but not objectionable. I have good flowing heads with a relatively small roller cam. I can drive it anywhere in any traffic conditions. Gonna put the A/C back in this year and expect it to be fine. It will still run easy mid 11's.
     
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