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305 heads on a 406?

Discussion in 'The Garage' started by shupach, Jan 28, 2003.

  1. shupach

    shupach 1/2 ton status

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    heres the story, i ordered a set of heads off of ebay a while back, they are supposed to be 64cc heads w/ larger valves (2.02/1.6) cast iron heads, well this was over the summer and im finally able to build my engine now, i decided to get the casting number off of the heads before i install them and see exactly where they're from and the number is 14014416, these are supposed to be 58cc heads off of a 305 from 1980-1985, most sources said 305 while others said that they also went on the 350. Im gonna call the seller tomorrow and talk to him, but aside from that, how will these heads work on my engine?
    engine setup right now: 400 bored .030 over, 5.7 forged rods, flattop hyperuetectic pistons, comp cams 4x4 cam w/ 270/278 duration(at .006) and .480/.498 lift, holley dual plenum intake manifold w/ a holley 750 cfm carb. the computer dyno(dyno2000) shows that i will have around 500 lb/ft and a little over 400 hp, would this be correct?

    phill
     
  2. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    not to change the subject but how do your estimated hp and tq like you did?
     
  3. COCHEV

    COCHEV 1/2 ton status

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    you'll have to drill steem holes. i have some 305 heads i want to use to. supposed to be great for torque and bump the comp. up a bit. perfect for offroading. kindof a heated debate on this though. do some searching here been covered a lot on this board
     
  4. shupach

    shupach 1/2 ton status

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    i have a computer program where u enter the specs of the engine and it estimates the tq/hp readings at the fly
    and yes i have the steam holes drilled

    phill
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    58 cc chambers and flat tops will bump your CR up to over 10:1. I'd consider heads that will flow better than 305 heads...you're gonna choke that motor.

    Rene
     
  6. shupach

    shupach 1/2 ton status

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    wouldnt a port and polish help the flow, just throwing out ideas, i think im gonna run this and see wat happens.

    phill
     
  7. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    where did u get the program and how much did it cost you?
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Port and polish would help the flow, so would port matching. I'm still not sure what you're gonna do about the CR. You're gonna be compressing a rather large volume into a very small chamber. You might have a fair bit of knocking and pinging...the heads are cast iron so that isn't going to help any either.

    It may run, but I predict it will be more trouble than it's worth.

    rene
     
  9. Sandman

    Sandman 3/4 ton status Author

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    You are going to end up with a huge amount of compression. Just swapping in flat tops will put those 400's to 10:1. It might just be too high. Unless you stick in dished pistons.
     
  10. ben427

    ben427 1/2 ton status

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    If i were you id get some 76CC 882's or large chamber aluminum heads. The 882's flow pretty decent and the large chamber will keep your compresion reasonable for pump gas.
    Im building a 400 and am going to use 18 cc dish piston with 76 cc heads for 9.5:1 compression, which is still streching it for pump gas.
     
  11. bigmack

    bigmack 1/2 ton status

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    Like everyone else has said, the compression will be way up there. I have a .30 over 400 in my truck, the pistons are TRW forged flat tops with 2 valve reliefs, my heads are '68 model 291 double humps, they have 64cc combustion chambers, so that puts my compression ratio at about 11 to 1. It will run OK on 93 octane gas but really likes a few gallons of 110 octane. I would suggest that you check with the piston manufacturer, they will be able to give you a close estimate on what your compression ratio would end up at. Or if you can find your piston listed at Jegs, or Summit alot of times they will have CR info there.
     
  12. big pappa b

    big pappa b 3/4 ton status

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    How also did u get a HP figure? What compression ratio did u use in the program? If your pistons were supposed to be 10:1, most likely it was based on a 72 or 76cc head. If you put on those 58cc heads your compression is gonna be somewhere in the 11.5 to 12:1 compression ratio. That's definitely a NO-GO for the street unless you want to run race gas all the time
     
  13. shupach

    shupach 1/2 ton status

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    i got the pistons from summit and these heads have had some work done to them so they are 64cc, summit claims that the cr will be 10.84:1 which is high i know, but this isnt a daily driver and the airport is 5 min away incase i need some 115 octane stuff. i'm gonna go ahead and try it, i have a set of 76cc stockers lying in the garage that'll go on if the engine gives me hell.

    phill
     

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