1968 300 camshaft questions

Engine, Transmission & Driveline

  1. brunickw

    brunickw New Member

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    So I should set it around 12 - 14 BTDC then do the break in cycle, then go drive it and adjust it by ear?
     
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  2. Ripinator

    Ripinator Senior Member

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    Yes.
     
  3. bajajoaquin

    bajajoaquin Senior Member

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    If you are torn between two cams, they say always go with the smaller one. You may have noticed that nobody recommended a cam with more than 230* of duration at 0.050” lift
     
  4. 65sporty

    65sporty Old Man with a Hat

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    12-14 initial should be good, usually about 36 total all in by 3000 rpm. You can tune it be ear, but I would check it with the light after to see how much initial timing it has. Do you have a dial back timing light so you can check total timing or a timing tape on the balancer?
     
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  5. Mike66Chryslers

    Mike66Chryslers Well-Known Member

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    I agree. Setting the initial timing does not tell you what your timing will be at high RPM, which is where it is most important to generate power and not detonation, unless you know how many degrees of mechanical advance are built into your distributor. The ideal way is to set 34-36 all-in timing, which requires a dial-back light or timing tape on the balancer. Then see what the initial timing is once you let the engine fall back to idle. If the initial is not where you want it, modify the mechanical advance in the distributor to limit the travel. Then at WOT if you get ping at mid-range RPM which goes away at high RPM, the mechanical advance is coming in too soon, so you need to change to heavier springs. Once that is all dialed-in, connect vacuum advance to the timed vacuum port and set that up.
     
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  6. brunickw

    brunickw New Member

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    Ok so I went and bought a new timing light, Its the Innova 5568 pro timing light, local tool store was going out of buisness and they had one on sale for $40 brand new in the box. So this new timing light should have the ability to check the all-in-timing, I think. The timing light has a tach built into it so I check the all in timing at 3,000 RPM correct?
     
  7. stubs300

    stubs300 Senior Member

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    Nice light, You stole that puppy!!!! Innova Pro Timing Lights 5568
    It should be able to, I haven't read the directions. What do they say you can do with it? Good Luck
     
  8. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    If distributor is stock you should go to about 3500 to set total timing. 36° is about right for a open chamber BB Mopar. Once you get the cam broken in you can use the rpm function on the light to see when the timing mark stops advancing, then just make the total of 36° at or above that rpm.
    Initial timing can be set for highest vacuum possible at idle. Then see where your total ends up at and adjust from there. Most BB have 20-22° mechanical advance from the factory. 36°- 22°= 14°, that's where the 14-16 number comes from, it's kind of generic but it works. If the engine has a lot of carbon in combustion chamber, carburetor is lean at cruise, or runs hot you may not make it to 36 ° total without pinging/detonating, then you will have to pull it back.
    Good luck
    Make sure that thing starts immediately and goes directly to 2000+ rpm. Make sure you use oil with lots of zinc, not added to regular oil.
     
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  9. saylor

    saylor Senior Member

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    for 30 minutes. i just got thru talking to comp cams about it because my engine gets too hot to run 30 minutes in one shot. i asked them if i could stop and take time to dial in the timing. they said run 3x 10 minutes. i asked them whats more important - heat cycles, or run time. they said 30 minutes.

    try not to die your cam -

    - saylor
     
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  10. bajajoaquin

    bajajoaquin Senior Member

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    Can you spray water on the radiator?
     
  11. Ripinator

    Ripinator Senior Member

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    Saylor: To keep the engine cooler during cam break-in, open the drain petcock a little and stuff a garden hose in the filler neck at the top of the radiator, and adjust the flow so the amount of water going in is about the same as the amount draining out. Also, position a running window fan in front of the radiator. You should then be able to run the engine as long as you need (in one shot) to break in the cam.
     
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  12. stubs300

    stubs300 Senior Member

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    It sounds like you need to address a cooling issue pronto!
     
  13. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    I would do the cycles back to back, allowing for cooling down between rounds. The reason for the high rpm break in is to splash the cam with oil, shutting it off is not splashing oil and the cam starts to drip dry. The time running with plenty of zinc rich oil splashing on the cam builds up a layer of ZDDP that protects when oil splash is not high ie. idle or low rpm speed.
    This is a constant build up and tear down of this layer through the life of the engine.
     
  14. brunickw

    brunickw New Member

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    Ok so I got the cam broke in and new exhaust on it, I have the timing set 12 degrees at idle but it's at 40 degrees at 3000 rpm. So I need to adjust the advance down to about 36 degrees right? How do I go about doing that in this distributor? I tried playing around with it but no luck.

    20190918_172131.jpg
     
  15. brunickw

    brunickw New Member

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    I pulled the rotor off and there was a screw and snap ring under it. But the guts still wouldn't come out.

    20190918_172123.jpg
     
  16. brunickw

    brunickw New Member

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    I also tried taking the screws out of vacuum can.

    20190918_172113.jpg
     
  17. Mike66Chryslers

    Mike66Chryslers Well-Known Member

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    I've never seen a dizzy like that. You said in your initial post that it is a Pertronix unit. Do you have the manual for it? Looked on their website for a PDF copy?
     
  18. Ripinator

    Ripinator Senior Member

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    I would drive it around a bit and see how it runs. If it doesn't ping, it may be yer engine is happy with a total of 40 degrees. If it pings, just retard the distributor in small increments, until the ping goes away.
     
  19. brunickw

    brunickw New Member

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    Ya I thought it was the pertronix but after messing with it i realized it wasn't. The previous owner had put it in so i dont have the manual or anything. I cant even find a brand name or anything on it. Ya I will drive it around and see if it pings or not. I just thought 40 would be way to high.
     
  20. Ripinator

    Ripinator Senior Member

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    One more thing: I assume you had the vacuum advance disconnected and the vacuum port at the carburetor blocked when you set the initial timing to 12 degrees, didn't you? I say this because some times when I do this, I forget to do that