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Big block experts - opinions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by k5kraze, Mar 20, 2001.

  1. k5kraze

    k5kraze Registered Member

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    Location:
    AUSTRIA, A-7041 Wulkaprodersdorf
    I am in the process of building a 468 big block. The parts:

    454 block, 0.060 over
    Stock 4.00 stroke cast crank
    Stock (reconditioned) rods with arp bolts
    Keith Black Silvolite Pistons, about 9.2:1 compr.
    Weiand Stealth Oval Port Intake
    Comp Cams Xtreme Energy hydraulic cams with about 0.515/0.530 lift

    I am not sure about the heads as i want to build the engine mainly for torque, but a little top-end powerwould not hurt. My budget is tight, so aluminum heads are out of reach. The candidates are:

    World Product Merlin (oval port, 269 cc intake runner)
    GM 188 or 990 castings (rectangular, 317 cc intake runner)

    Several sources on the net say that the Merlin (even with smaller runners) flows a little bit better than the GM head, on the other hand, the GM castings are hard to beat price-wise (about 480$ ea vs. 650-700$ for the Merlins, both ready to bolt-on). The Merlins have a bigger 2.25 intake valve (GM: 2.19), exhaust is identical with 1.88.
    Now my question: Are the differences in flow really that significant for a off-road vehicle?
    Has anybody experiences with one of these heads?
    Will the cast crank hold up (projected power level: 450-500 hp) ?

    Any help is appreciated!

    Thanks in advance

    "DO IT TODAY, TOMORROW IT COULD BE ILLEGAL!"
     
  2. Shawn

    Shawn 1/2 ton status Premium Member Author

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    For a 4x4, I'd stick with oval ports and 2.19 valves. Unless you plan on running the engine past 6000 rpm, the ovals should be fine. Merlins are still a good chunk a change ($1000 complete). Last week, I posted a 25% off carparts.com coupon which would of made complete Edelbrock alum heads $1200. I think it expired yesterday though. Thats still some serious cash though. Have you considered a used set of 049 oval heads? I have a fresh set that have just been rebuilt with 2.19 and 1.88 valves. I couldn't use them since the larger valves made the combustion chamber 117cc (needed 110 or less). The cast crank should be fine up to 6000rpm.

    Shawn
    87 K5
    few mods[​IMG]
    <A target="_blank" HREF=http://www.off-road.com/chevy>http://www.off-road.com/chevy</A>
     
  3. k5kraze

    k5kraze Registered Member

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    Location:
    AUSTRIA, A-7041 Wulkaprodersdorf
    The problem is that I live in Austria and big blocks (or any american-built V-8s) are very rare here. Maybe it has got something to do with the gas prices in my country (currently about 4 $ per gallon) :-(.
    Are the 049 castings you mentioned still available new and what are the advantages over 990 or 188 castings ?

    thanks in advance
     
  4. Shawn

    Shawn 1/2 ton status Premium Member Author

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    Oh... I didn't see where you lived so that changes everything. The 049 heads are only found on the early 70 big blocks and it sounds like won't ever come across any. I guess I'd go with the Merlins and pay a little more. The Merlins would be more ideal for a 4x4. The 188 and 990 heads are the same thing and are interchangable. GM part # on those heads is 6260482. If you're planning on making a high RPM, high HP engine, then I'd consider the rectangle ports. A good source of information is a book called Big Block Chevy Performance writen by Dave Emanuel. Not sure if you can get any book like that but I do know Amazon.com carries it.

    Shawn
    87 K5
    few mods[​IMG]
    <A target="_blank" HREF=http://www.off-road.com/chevy>http://www.off-road.com/chevy</A>
     
  5. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I would most definitely choose the Merlins over anything else for daily driver. I have many info on these heads, and they are AWESOME!!! They can outflow a stock LS6 head. I have all the info. When the time comes to rebuild my beloved 85 K30's 454, I am going to use the Merlin oval port heads.
     

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