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2 ?'s about heads pistons and CR

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ftn96, Nov 12, 2001.

  1. ftn96

    ftn96 1/2 ton status

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    2 ?\'s about heads pistons and CR

    Im looking at getting new heads for the new motor. Was thinking Vortec's. However, SInce I've done some more reading Im thinking about the World S/R Torquer heads because of the 2.02/1.60 valve size, but they come in 76cc versions for the 87+ intake style. I was wanting to run flat top pistons with 67cc heads.
    So my questions are, is there any draw backs to using domed pistons with the 76cc heads?
    Or should I stay with the 67cc heads and go with flat tops?
    OR just get the damn vortecs and stay with 64 and dished P's?
    I want my Compression ratio to be at or slightly below
    9.5-1.....
    Thanks for your help in advance

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  2. HarryH3

    HarryH3 1 ton status Author

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    Re: 2 ?\'s about heads pistons and CR

    Those valve sizes are great if you're building a 7,000 RPM drag race motor. They won't do much for (or may even hurt) low end torque. Quit dreaming over the Summit and Jegs catalogs and build your engine already! [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  3. 55Willy

    55Willy 3/4 ton status

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    Re: 2 ?\'s about heads pistons and CR

    I would go with flat tops and the Vortecs. Add a good heathy low end cam and call it good. If it ain't enough power fo ryou throw on one of those blue bottles[​IMG]

    <font color=red>Life is like a mud hole:</font color=red><font color=blue>
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  4. ftn96

    ftn96 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    LOL!!! Thats funny you should say that HAIR-E... I have too much time to think about it.
    According to my 350 rebuild book, the 2.02 heads are more desirable cause it allows the motor to breath at the bottom end to allow for more torque. Thus the name Torquer heads.
    Just trying to make sure I'm happy with my final results. [​IMG]

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  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: 2 ?\'s about heads pistons and CR

    Most guys want the 2.02's for high rpm's...1.94" heads work great for low end and offer a great mid-range. The slightly smaller intake size will help low end torque, not hinder it.

    I would stick with the Vortech's...

    Rene

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  6. HarryH3

    HarryH3 1 ton status Author

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    Re: 2 ?\'s about heads pistons and CR

    But you need to understand who's talking when they talk about "bottom end". To a drag racer, 3,000 RPM (or even higher!) is the bottom end because that's where their torque convertor stalls. The engine revs freely up until that point. To a rock crawler, 1,200 RPM is the bottom end. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  7. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    I will step up and say the Torquers are a great head. I had the same cylinder heads on a Firebird that was a summer street car (w/ a good bit of pep of course [​IMG]). It was a 355 w/ a middle of the road cam, and about 10.8 to 1 compression ratio and that sucker flat out flew. Was a great car, and while the low end torque wasn't bad, it definetly wasn't the best either IMO. Obviously my cam choice cam into play as well, but I think for a 350 the vortechs would fair better in a truck/offroad rig. In fact for a street cruiser there may not be a better head for torque IMO.

    I think you're worrying a little too much on what pistons you use... I'd be much more worried about a cam selection as with the FI it will pretty much be the biggest factor in performance.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
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  8. Blazer1970

    Blazer1970 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    Flat tops with 76 cc heads will give you about 9.5:1. Dished pistons with 64 cc heads will also give you about 9.5:1. Flat tops with the 64 cc heads will put you over 10:1. Numbers are ball-park, depending on the exact volume of the dish/valve reliefs on the pistons, head gasket thickness, etc.

    Tim

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  9. Re: 2 ?\'s about heads pistons and CR

    The Dart SR's make good bottom/mid range power.They due have 2.02 valves but the port designe and runner volume make the larger valves scavenge more air at lower rpm's.
    But they still flow decent in the upper mid range also.They're a dam good head for the money.IMO But the Vortec's are built on new tech and make great power in the same power range.
    I dont think you'll see enough power difference to say one is better than the other.Either head is a damn shot better than whats on there now so you cant realy go wrong with either head.

    Now just buy something and quite debating and start building!!
    LMAO!!
     
  10. ftn96

    ftn96 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    Well, I have to wait for the machine shop to gimme back the motor anyway. I cant buy anything till they give me some numbers. should be this week sometime. It didn't have any ridges at the tops of the cylinders, so hopefully a hone is all it needed. If thats all thats needed I could use the old ones.
    I need soem help I dentifying them though. The only markings on this piston is a dished looking object with a 12 in the dished area and the number 805 under the object. Im assuming the 12 means 12cc dished, but the 805????

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  11. ftn96

    ftn96 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    Also at what point would screw in rocker studs become a factor? Obviously if I have them and the springs aren't maxing them out then that would give me good over head for longer life.
    Just asking for my education. Go ahead tell me to stop asking and go order. [​IMG]

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  12. Re: 2 ?\'s about heads pistons and CR

    For smaller spring rates its realy not much of a factor.But their always nice to have for the exta comfort of knowing your not going to pull out.LOL
     
  13. ftn96

    ftn96 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    exactly what I was thinking. According to my compression calculator and providing that my block hasn't been decked....
    If I get the 67cc S/R torquers with 2.02/1.60's I can use the 12cc dished pistons I have, using a stock .039 head gasket this would put me at 9.3437 CR.
    I think this is the route Im gonna go, providing that these heads except 87 up intake style manifolds. Damn catalogs just dont give enuff information these days. [​IMG]

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  14. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    I believe the Torquers are made by World Performance products. You might be able to find a place online or a home page for them. I used to have their page bookmarked but it comes up Not Found so they probably moved.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
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  15. Zepplin

    Zepplin 1/2 ton status

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    Re: 2 ?\'s about heads pistons and CR

    Their website is http://community.webshots.com/user/zepplin1976
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: 2 ?\'s about heads pistons and CR

    Dads original 1968 375hp 327 heads (Vette) had pressed in studs that were JUST getting loose. That motor I'm sure has been abused, and although I don't know cam selection then, probably a high lift cam with pretty stout springs. In any case, lower lift (below .450) is going to keep you pretty safe for many years. I researched it to (screw in for the Vortecs) but with my "low" RPM usage and low lift cam, the press-ins aren't going to fail anytime soon.

    Dorian
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