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Technical Porting Power Pack SBC Heads

Discussion in 'The Hokey Ass Message Board' started by BOSTONCAMARO, Feb 17, 2024.

  1. I know new heads can be bought cheap and yield
    way more power, dependability etc.

    I ended up with a set of Power Pack heads, "520"
    casting number for next to nothing with tons of work done to them, just machined, bronze guides etc.

    I just want to do some mild clean up on intake and exhaust ports (have ported many sets of heads over the years etc).

    I dont think I will be using a Felpro 1205 to scribe what is to be ported.

    Does anyone have a recommendation on intake and exhaust gasket to use for port matching?

    These will go on a high compression 60 over 283 that I have all the parts for. I want it to be a period build.

    Thanks, Tim
    Deuces, GlassThamesDoug and Just.dale like this.
  2. Just.dale
    Joined: Dec 4, 2018
    Posts: 324


    Can’t answer your question but I had a 60 over 11.1 compression 283 in my 64 Chevy 11 back in high school, whew!!! What a ride!!!! The only car I wish I had kept. Have fun!!!
    Deuces and BOSTONCAMARO like this.
  3. Tossed a couple valves in

    Attached Files:

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  4. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,872

    jimmy six

    As many times as I’ve tried by standing back from my bench about 5’ and “tossing” a valve at the guide hole I’ve never had one go in. It’s an honor to meet a man on the HAMB be able to do 2 in the same combustion chamber…. I bow to you Sir BOSTONCAMARO!
    Last edited: Feb 18, 2024

  5. I have some ported power pack heads.
    My machinist gave em to me
    Putting em in my 283.
  6. Any pics of these Anthony?
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  7. Haha good one Jimmy!
    Deuces and jimmy six like this.
  8. I can get some probably tomorrow
    Probably more polished than ported
  9. Mike VV
    Joined: Sep 28, 2010
    Posts: 3,037

    Mike VV
    from SoCal

    There's no real sense in a larger gasket, and porting to it !

    Unless you properly widen the "pushrod pinch"...FULLY, from top to bottom, a huge gasket opening will net you...near zero profit !
    Add to that, a VERY careful cleanup of the short turn radius (bottom of the port just inside of the valve, both the intake and exahust.
    DO NOT LOWER THE PORT FLOOR, under ANY circumstances. Smoothing it's fine, that is removing any casting marks and smoothing the casting bumps is ALL that should be done.

    Just scribe "straight" lines at the widest point of each wall, and grind to those lines. Again...NO need in making the port larger.

    Smooth all of the sharp edges in the bowls, blend smoothly to the seat.

    And a proper three angle valve seat...WITH...a 30° back cut on the intake valves, to just shy of the seat diameter.
    NOTE - make sure that the machinist makes the 45° seat "almost" (about .02" shy of the OD.) to the edge of the valve. Specifically the intake valves.

    BOSTONCAMARO and Tow Truck Tom like this.
  10. I haven't done a 'word search' but the impression I have is that there are too few "porting" discussions around this place.
    Your skills at trimming a gasket faithfully and transferring the 'image' of the head ports are more important than what gasket you use.
  11. I have a set of ported power pack heads that were hogged WAY out. They even put 2.05 and 1.60 valves in them if that tells you anything. They looked good when I got them but I figured I should freshen them up for an engine I was building. When I took them to get checked out, they wouldn’t hold a vacuum on a couple of the intake ports. We figured out that they ported them a little too far and two intake ports had a hole across them. Anyway, we were able to weld up that screw up but I still haven’t used them on anything. I honestly can’t believe how much time someone spent on the set I have.
  12. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,939


    Yes ....... It's called Gasket Paper. [port matching to the intake and exhaust gaskets is old school thinking]

    If you "bell mouth" the intake port and the intake manifold to match the gasket, you create the opposite effect of a venturi [and velocity stalls in this area]

    You are better off using gasket paper to match the intake port to the manifold [to whichever side is larger]
    On a flow bench "gasket matching" can lower flow by 10 to 15 CFM [if the head is tested with the manifold bolted to it]
    An oversized gasket has negligible effect on flow if the ports are matched to the manifold [I've seen the results of this where we tested without a gasket, then sandwiched one in between and tested again]
    Last edited: Feb 18, 2024
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  13. mustangsix
    Joined: Mar 7, 2005
    Posts: 1,406


    I once spent a boatload of time porting some heads only to find that they didn't flow as well as a stock set of vortecs....:(
    jimmy six and guthriesmith like this.
  14. DDDenny
    Joined: Feb 6, 2015
    Posts: 19,203

    from oregon

    This is an age old scenario proven many times over by actual people that know what they are talking about, so what I'm saying is............what's the point!
    If you want a drivable and dependable street a 301, (or a 327) with a set of 1.94 heads, a matching intake (many choices) and a "middle of the page" camshaft, again, there are far too many to suggest.
    Another point, a four speed and rear gear in the 3.70 range will do wonders with these little small blocks.
  15. Joe H
    Joined: Feb 10, 2008
    Posts: 1,542

    Joe H

    To truly port match them, bolt the heads to the block using the correct head gaskets, bolt the intake on and torque it down, then drill four 1/8" holes, one at each end of the manifold through the gasket and in to the head just enough to hold a roll pin. Now when you take it all back apart, use 1/8" pins to locate the gasket on the head and cut the head to match the gasket. Once the head matches the gasket, move the pins and gasket to the intake and match it. Be sure to blend any cuts as far into the port as you can to keep from bell mouthing, you want on continuous wall with no protrusions or divots. When assembling the final time, use the pins to help align the gaskets and intake to the heads.
    BOSTONCAMARO and jimmy six like this.
  16. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,872

    jimmy six

    Excellent and the correct way. Time consuming but anything worth doing is. Many times working in the manifold is more rewarding to your engine if you can increase air velocity at the opening of the valve.
    BOSTONCAMARO likes this.
  17. Thanks for the insight, have ported many sets of heads through the years witb good success. I worked as a mechanic for many years including time at a speed shop and crewed on my friend's dragster which was real competitive. Hoping some decent clean up will wake these up a bit, I have serious Track 1's on another motor, but am purposely building this with an old school vibe, high compression pistons etc.
  18. Not looking for driveable, likely will go in my 27 T coupe that I will trailer to track, sometimes drive on street.
  19. Getting there

    Attached Files:

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  20. Deuces
    Joined: Nov 3, 2009
    Posts: 23,854


    Fixed the picture....;) IMG_9033 (1).jpeg
    loudbang and BOSTONCAMARO like this.
  21. Not sure why my pics always upload like that
  22. Joe H
    Joined: Feb 10, 2008
    Posts: 1,542

    Joe H

    I like your porting location, I try and do all mine outside as well, better light and ventilation, bonus is the easy clean up.

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