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1.6 rockers and elongating the heads to support them????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by twenty_below0, May 17, 2002.

  1. twenty_below0

    twenty_below0 1/2 ton status

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    OK, just as it says, I need to do this to support the rockers and am wondering how much?? ( these heads have the rectangular holes for the pushrods not round like the newer heads) , can I drill these out an 1/8" wider and longer ?? Is this enough, and do i need to worrry about damaging the head by drilling to much ? Any other idea's welcomed!
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If you make the slots wider then there is nothing to guide the pushrods unless you install screw-in studs and guide plates. You need to make the slots longer not wider. You really should not even need to do anything to the slots with 1.6 ratio rockers unless you have tons of valve lift.
     
  3. rusty79

    rusty79 1/2 ton status

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    not to butt in on your post but 1.6 rockers just make the cam act like it is bigger right extending your valve lift?
     
  4. twenty_below0

    twenty_below0 1/2 ton status

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    Yes in a way,.. I was told by the tech's at P.A.W. that it would increase the bottom end torque noticeably, .....so I will run them and see if it's worth it.
     
  5. twenty_below0

    twenty_below0 1/2 ton status

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    The cam I am running is going to have a total lift of .498 intake and .510 exhaust with the 1.6 rockers, and as far as wider I am running self centering roller rockers with pinned studs they said that with the self centering rockers, guide plates aren't necessary ....is this accurate and will they need to be longer with this cam lift or not? THX appreciate the info!!
     
  6. chevyracing

    chevyracing 1/2 ton status

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    Never heard of anyone having to machine a head to make longer rockers fit. I have read articles in Hot Rod and Chevy High Performance where they have run 1.6 rockers on the corners and 1.5 everywhere else and got results that way and never mentioned any machining..
    The thing you need to watch for with a high lift cam is bind. Make sure the push rods will not bind against the guide and seat for the rocker. Also make sure your springs will not have coil bind.
    I am wandering off topic here. Later.

    John
     
  7. m j

    m j 1/2 ton status

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    it is funny how for decades chev guys poo poo'd that ford used that style of rocker alignment, touting the dangers of dropin a valve.
    then chev copies it and it is all cool again...
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I personally do not like the self aligning rockers. I would rather install guide plates and screw-in studs that are much stronger than any factory stud especially since there is going to be an aftermarket cam with more lift and duration than stock which happens to stress the valve train more. I also would use a true roller rocker of a qaulity brand such as comp cams or crane that have a higher rocker ratio accuracy rate than cheaper brands.
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I may not be understanding you correctly but, when a cam is installed in an engine that has enough valve lift the pushrod may bind in the slot in the head which aligns the rocker. You must either elongate the slot to accommodate the high lift or drill the pushrod slot to 3/8" and then use screw-in studs and guide plates. And don't forget if using guide plates you must also use hardened pushrods or the pushrods will fail where they rub on the guide plates. You are very correct about checking for coil bind on the valve springs. As a general rule you should have at least .100" clearance on the exhaust springs and .050" on the intake springs. These are safe limits to adhere by.
     
  10. m j

    m j 1/2 ton status

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    from what I have seen comp and crane rollers (at least the common ones) are not very high quality looking
     
  11. twenty_below0

    twenty_below0 1/2 ton status

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    I have used comp in the past and never had a problem just not the 1.6 ratio, I am going to run a different set of heads in a few months (Canfields) but for now I will use these and the pinned studs, they are an old set of double humps, I guess I will just have to check bind and clearance when they are on it.I talked with another tech at P.A.W. today and he said with older GM heads you shouldn't have to longate them unless it's a really large cam.......... it's funny how one tech says this and another says you must longate them??? Go figure
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Yer using the correct valves for self centering (also known as "rail") rockers right?

    With standard length valve stems and rail rockers, you run the risk of pushing the spring retainer down, and letting the locks loose. Stock rail rocker types (like Vortec) use different length valve stems to prevent this from happening.
     

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