Vortec Cylinder Heads: The Definitive Guide

Discussion in 'Engine Topic' started by MikeM79, Jul 4, 2006.

  1. fiscus

    fiscus Veteran Member

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    I bought the ARPs because I read something about vortecs requiring a special bolt, but I felt I would have been just as well off using hardware store bolts, they are just a basic bolt made from fancy material; for 11lb-ft, I don't think they are necessary.
     
  2. 73 DEVILLE

    73 DEVILLE Member

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    Thanks again Dirt. I just PM you.
     
  3. Alex71RS

    Alex71RS Veteran Member

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    Dirt, if you could PM me with the same article, I would be most appreciative.
     
  4. Alex71RS

    Alex71RS Veteran Member

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    I just received Brian's (Hardline_42) cutter tool in the mail tonight, and decided to see how well it worked. I went slow to ensure that I didn't cut too much, and the tool cuts the cast iron easily.

    Here's my question: The Comp tool makes two cuts at once (the guide diameter and the guide height). I'm using a Lunati spring (73943) that has the same o.d. as the stock Vortec spring, so cutting the pockets for a bigger spring is not required. I removed the stock GM valve seals and measured the distance between the uncut (stock height) guide boss and the bottom of the retainer and got a measurement of .703" . I went to an adjacent guide boss and began to cut. The o.d. of the guide gets cut first, and when you get to a certain point, the top of the guide boss begins to get cut. I cut the guide boss height to a point where measuring from the same points as I noted above, I got a measurement of .814" , a gain of .111". Where is a good stopping point? All of the pictures I have seen of modified guide bosses also shows the larger spring pockets, and it appears from those pictures that the .531" o.d. that the cutter tool created goes all the way down to the spring contact area. Every factory cylinder head (487, 461, 186) I have in the shop has at least a .200" boss height from the spring pocket. Is this because the factory used single wire springs and the boss diameter at the base wasn't critical? If I keep cutting the guide boss diameter (.531") all the way down to the spring pocket, then the guide boss height is going to be really short. Is this what the cutter is designed to do? I would rather stop and ask questions than cut away and possibly do damage that I can't reverse. Plus, my Lunati springs have an inner spring, and if I left my guide boss as it is right now, it would appear that the inner spring would be resting directly on top of the boss with the spring installed. What do you think? Keep cutting and make the guide .531" all the way to the spring pocket?

    Sorry for the long-winded explanation......
     
  5. Dirt Reynolds

    Dirt Reynolds Veteran Member Lifetime Gold Member

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    Story is sent, guys. :cool:

    Anyone else who wants it, just PM me instead of posting here. That way we minimize clutter of the topic with requests, thanks. :)
     
  6. hardline_42

    hardline_42 Veteran Member Lifetime Gold Member

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    Alex, the cutter is designed to cut the boss so that it will accept a .530 postive type valve seal with the relationship between the OD cut and the height cut being exact for the seal to seat correctly. You don't need to cut the boss down to the spring pocket, only as much as is necessary to get the clearance you need. I assumed the same on the first set of heads I ever did and cut the boss down to the spring seat. There were no catastrophic results except that the valve guide wore a little faster because of less material. If your springs are drop-in, the extra meat left on the boss at the spring seat shouldn't be a problem. Let me know how it works out. Pics would be helpful too if you have any additional q's. Good luck!
     
  7. Alex71RS

    Alex71RS Veteran Member

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    Thanks for the reply, Brian. That puts me at ease. Yesterday, I called my buddy who builds race motors and he echoed exactly what you said. It was those pictures in the Car Craft article that showed the guide at .530 all the way down to the spring seat that was throwing me. Now I just need to figure out by doing the math if I need to cut any more.

    I am going to figure in the .030 safety margin and the thickness of the PC seal, and add in my max lift (.507). I think I'm good to go with what I've got right now. I may possibly go with a 1.6 rocker on the intake, so I'll figure that in, too.
     
  8. stickles

    stickles Veteran Member

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    i read somewhere that the vortecs better with a cam that had a .01 difference from front to back(.484 to .494). is this true or would it run just as well with a .484 lift cam?
     
  9. hardline_42

    hardline_42 Veteran Member Lifetime Gold Member

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    Personally, I've never heard of the ".01" being a magic number or anything. In most cases though, stock Vortecs do better with a split pattern cam that has more lift and duration on the exhaust side to make up for the low exhaust flow.
     
  10. stickles

    stickles Veteran Member

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    the .01 was just an example is all. i have a set of vortecs that are going on my 350. i know they have .202 valves with z28 springs and have been ported.
     

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