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BBC build advice needed

Discussion in 'The Garage' started by 77crewcab, Oct 25, 2006.

  1. 77crewcab

    77crewcab 1/2 ton status

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    I am rebuilding a 454 for my Crewcab and I am looking for some advice before I begin. The engine is from a 74 Chevelle/Monte Carlo and appears to be totally stock. The engine bore is still 4.25 and the heads have 2.08 Int/1.70 Exh valves. These are the 781 heads. I am looking at doing a .030 over bore and going with a cam approx. 208/218 dur and 485/515 lift, something with lots of low end grunt for towing and around town driving no need to top 5000rpm. I am really running into a problem deciding what to do about the heads though. The stock valves are in good shape, so should I reuse them and maybe do a small porting job to gasket match and remove casting flash from the ports. Or should I do the port job and step up to 2.19/1.88 valves. I know I will have to get some new springs to match the cam. Any of you that work in a machine shop able to give me an idea of what the machine work will run to check the heads for cracks and to upgrade to the larger valves?

    Also anyone with desktop dyno or such able to tell me what I would be looking at for hp/tq with this set up?
     
  2. rcamacho

    rcamacho 1/2 ton status

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    For low end I'd stay with the stock valve diameter. A pocket port would be beneficial in the midrange but probably not cost effective. I had my BBC heads pocket ported on the last rebuild but am running a hotter cam that does not really come alive until 2200 RPM
     
  3. JEBSR

    JEBSR 1/2 ton status

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    I upgraded to the 2190/188 valves, but I wanted more midrange power. I think I would port match with stock valves for a low rpm, high torque engine. But that's just my opinion.
     
  4. 77crewcab

    77crewcab 1/2 ton status

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    So if I keep the stock valves (saves money) would I still need to pay for a valve job or could I just lap the valves? any Idea what the stock spring ratings were? Wondering if I might be able to reuse them as well. My valve guides look good internally but a couple have some small nicks on the top where the seals would go. Is that anything to be worried about?
     
  5. 77crewcab

    77crewcab 1/2 ton status

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    Top...any other input?
     
  6. bigred81

    bigred81 1/2 ton status

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    Use a good set of flat top pistons and use a cam that is close to the stock 1974 cam specs because the cams those years were very good for power and pulling wise. My crew cab had a 1974 454 motor that I rebuilt using a cam that was close to the stock grinds and it would pull. The idle was a little rough but that was cause by the cam.

    bigred81
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd look at swapping every piece on the head out myself. Rebuilding a new engine, the last thing you want is to mushroom a valve tip or lose a spring after 1,000 miles and either tear up the engine, or at best have to tear it back down to fix the heads the right way.

    As expensive as BBC parts are, it might not be as cost effective as the SBC's, but for a small block, aftermarket heads are a better *overall* solution than refurbishing/reusing older stock heads.

    As to crack checking/magnufluxing, I like the idea, but as far as I've seen, if the shop "misses" a crack during testing, they won't do anything about it when you come back. Probably less a problem on a head than a block, but I know one person that had a block supposedly magnafluxed only to have the crankcase fill with water as soon as he started pouring it in the system. IMO another reason to go new, IF the cost isn't outrageous.
     
  8. 77crewcab

    77crewcab 1/2 ton status

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    Okay well as for new heads I have looked at the Edelbrock performers and the aluminum ones from Jegs both around the $850 mark and would save some weight. I would like to use the 781 heads since they are in good shape, however if the machine work sends the price up close to buying new heads then I will have to rethink that. Right now I am really thinking of just getting springs to match the cam and either reuse the valves or buy some new ones in stock size, do a small port job and call it good.
     
  9. 77crewcab

    77crewcab 1/2 ton status

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