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new motor break in suggestions

Discussion in 'The Garage' started by DUKE, Oct 29, 2002.

  1. DUKE

    DUKE 1/2 ton status

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    have a new toy, with a new 350 in it. I've heard lots of ways to break em in, but I have to ask the ones I trust here. The concern is I might be forced to drive it upto 300miles from the nearest drop off place. It also dose not have pipes on it, just headers. Best way to break it in before the trip?







    for those that need to know it is a 73 nova almost ss
     
  2. ABO

    ABO Registered Member

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    I'd say to brake in the cam first, Run it around 2300 rpm constantly for about 20 minutes, that is unless thats already done. Change the oil and filter. Keep it under 50-55. Try to keep vairing the speeds. Don't put a load on the engine like going up a hill in third. I think It was Car Craft that recomended for the first drive to gun it to 35 drop it to 10 like 10 times, so that everything starts to seat correctly. I'm staying under 50 for at least 500 miles with my new rebuild. The open headders, I would suggest getting something on it but I don't know what type of adverse effect the open exhaust would have on the engine just know that you'll have a hell of a headace. Good Luck
     
  3. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    but I don't know what type of adverse effect the open exhaust would have on the engine

    [/ QUOTE ]

    You run the risk of burning a valve with too little restriction. I would put some sort of exhaust/muffler on it, even if you change it later. Just my $.02
     
  4. zakk

    zakk 1/2 ton status

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    i have never heard of this. i broke mine in w/o mufflers and nothing happened.

    THE most important thing is to prime the oiling system. if everything is nice and lubed up, start up will be less of a shock to the system.

    Second: vary RPM's for 10-200 minutes between 2200-3000 AFTER a good ten minutes of 2500 or so RPMs. this will ensure you do no flatten a cam lobe. having another person on hand to make and obvious carb tuning or timing adjustments would also be a big help.

    I am no mechanic, but this is how i broke in my 350 a few months back and it got me to school this morning so that i can type this to you. /forums/images/graemlins/thumb.gif
     
  5. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I'd put mufflers on it, with open exhaust you may not be able to hear any important sounds. /forums/images/graemlins/shocked.gif
     
  6. txbluethunder

    txbluethunder 1/2 ton status

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  7. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Exactly, I said you run the risk (not you would do damage). I should have clarified:
    Alot depends on head temps, timing, and jetting. If you are running really rich (good idea for new motor break-in) and proper timing you will most likely not have a problem.
    Burnt valves can happen for several reasons but all have one thing in common (excessive heating of the valve). One cause is is age. As the valve wears, it contact area with the head is diminished and doesn't trasfer heat as well. The valve gets "super warm" (sorry for the non-technical term) and distorts as it seats. The distortion allows gasses to pass (even when closed). Poor timing or lean mixture can also elevate temps of the head/valve and cause the same problem. Although running less restrictive/no exhaust in itself is not the issue (although you will lose low end power), the "side-effects" may. Proper exhaust will scavenge the hot exhaust gasses and transfer them down the pipes (reason for coating headers with ceramic coatings or wrap), this will keep the engine and compartment cooler. By using short/no exhaust, heat transfer becomes less efficient, head temps can increase (reason for high performance motors and diesels to use pyrometers on heads and/or exhaust). This can lead to valves running too hot and distorting. One issue too, is that is some damage may be done without even knowing it initially, but as the valve wears a little it will become a problem (reduced life).

    Again you/he may be alright, but it is something I wouldn't leave to chance. /forums/images/graemlins/thumb.gif
     
  8. bigblock454

    bigblock454 Clack Clack Clack Premium Member

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    besides the CAM breakin, engine breakin is almost worthless. Just like when you buy a new car, every single person that test drove that car before you got it hammered it several times to see how fast it was. Like racecar engines, you don't see Jeff Gordon (first one that came to mind) driving the first 500 miles at 50mph.
     

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