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Help with 350 rebuild- cam question

Discussion in 'The Garage' started by odoa3, Jul 6, 2004.

  1. odoa3

    odoa3 1/2 ton status

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    We are rebuilding the 350 out of my '75 K5. This is my first rebuild- newer than a newbie at this game- so I am relying on friends who have rebuilt a number of engines and have been wheeling for a while. The block is a late 60's early 70's - casting number 3970010.

    So here is the issue. Two people are saying that we have the right cam and two people are saying that the cam is the wrong one. When the cam gear and crank gear were install the dot on the cam gear was at 6 o'clock and the crank gear dot was at 12 o'clock. Timing mark on the harmonic balancer was about 180 degrees from where it was supposed to be according to the timing tab on the timing chain cover at top dead center. Two of my friends said this shows that we have the wrong cam. They say that in the mid 80's Chevy changed the cams and this is a cam for a mid 80's 350.

    My other two friends are saying that according to book (we are using the How to Rebuild Your Small-Block Chevy from HPBooks as a guide) everything is right. When it is on TDC the dot on the crank gear is at 12 o'clock and the dot on the cam gear is at 12 o'clock as well. Is this configuration the timing mark on the harmonic balancer matches up at 0 degrees with the timing tab on the timing chain cover.
    So, as you can imagine- with every single part in the engine other that connecting rods and intake being out of the box brand new- I want to be 100 percent sure before we we fire it up and start to ruin parts. Can you guys help me out? I hope I gave you enough information. If not let me know. Anyone help me out with this. Thanks. /forums/images/graemlins/1zhelp.gif
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Don't worry about where the crank is in reference to TDC. You did it right....line the dots up when you install a cam, which is 180* from TDC.
     
  3. backcountry

    backcountry 1/2 ton status

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    You shoud degree the cam in for max performance. Set it up as per your cam card. I did mine that way and used an offset bushing to set it 4 degrees advanced. /forums/images/graemlins/peace.gif

    Also, I have seen harmonic balancers that are messed up. For example: the inner section on the crank was fixed as per keyway, but outer portion had slipped on the rubber and rotated out of wack.

    There is a way to check if it has moved however i forgot the method. /forums/images/graemlins/dunno.gif
     
  4. odoa3

    odoa3 1/2 ton status

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    Thanks for the information guys.

    Another question. If we did have the wrong cam in- or the wrong grind on the cam wouldn't the firing order be random? I am thinking we have the right cam in - and when we were 180 out we hadn't turned the engine like Soulmate said. Any double checks or little tricks I can use to check the cam while it is in the engine. Or, just quit worrying and slap it in? /forums/images/graemlins/thinking.gif
     

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