?s for building a boosted big block..

Discussion in 'High Performance Modifications' started by mjoc, Feb 10, 2021.

  1. mjoc

    mjoc Veteran Member

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    Anyone have any links on what I should do to build a long block for a boosted application.
    I know I will be using an aftermarket block.
    I will be building a big block probably a 454 up to a 496..
    my first question is which is better a larger bore or a longer stroke? basically dont want to go to the extreme. in either but want to build a bullet proof motor that will hold a fair amount of boost either from turbo's or a single or pair of prochargers....
    I will be making it Fuel injected.
    Am I doing the right route thinking of getting a gen VI based block?
    If I run very good high end forged bottom end what boost levels would I be able to go for on the highend if I go with a good intercooled setup.
    THe engine still needs to be very very streetable 95% of the use will be on the street.

    thank you in advance
    Michael O'Connor
     
  2. 1980RS

    1980RS Veteran Member

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    About the only thing I would do for a high boosted BBC would be re-line hone the mains and add studs and o-ring the deck for a firing wire for use with copper head gaskets. I do think that with Cometic head gaskets that might not need to be done, you would have to check with others on that. Just make sure you use a good dampener as well. A Gen VI block would be a great starting point, better oiling than the Mark IV blocks.
     
  3. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    Big Blocks are tough. You of course want Forged Pistons, Studded Mains...
    For bore, you don't have any meaningful options on a factory block. You really don't want to go more than .040 over.
    A stroker 496 might not be the best choice for a couple of reasons
    1. With stroker engines, the piston pin moves into the ring-pack. This weakens the ring-lands and can be an issue under high cylinder pressures. It's generally not an issue on N/A motors, but Turbo engines can have insane cylinder pressures.
    2. The longer the stroke, all things equal, the higher the static compression. With a boosted engine, limited by octane and detonation, you generally want to run lower compression with more boost. You can run dished pistons, and larger combustion chambers to effect this, but it's fewer options.

    For boost levels, there are a lot of limiting factors.
    With a built engine, properly tuned EFI, and E85 fuel (E85 is 105 octane and cools the combustion chamber), you should be able to run well over 20PSI of boost. You're easily getting into the 700+ Horsepower range.

    It's worth noting here. You can buy a 540 Long Block, specifically setup for a Procharger from Sharioff for $13,000
    I doubt you could build the equivalent for less
    https://www.shafiroff.com/chevy-power-adder/540-long-block-power-adder.php
     
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  4. mjoc

    mjoc Veteran Member

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    Im Looking at Merlin BLocks They have two offerings for the Gen VI family of BBC they first has a 4.25 bore and a 4.50 bore both blocks can be bored out to 4.625 which I would never do. BUt I was wondering about stroke would it be better to go 4.25 bore and 4.5 stroke (option A) or go 4.5 bore and 4.25 stroke (option B) or how about 4.25 and 4.25 (option c) or should I got a route of like bigger bore and shorter stroke to like 4.0 inch or even smaller ???? I dont want to go too crazy cubic inch wise because it will be a semi daily driver about 10k miles a year..
    As for buying a sharaoiff engine that would be an optionn but I would like to try and build it myself even if it costs me more.. but will look into it.
     
    Last edited: Feb 12, 2021
  5. mjoc

    mjoc Veteran Member

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    So I called DART today and It Looks like I will be getting the DART Big M block it has a few versions available to me Im going to go with a standard 9.8 Inch DEck height but I am still trying to figure out what Bore I'm going to go with should I go with 4.250, 4.500, 4.560 or the max for the block at 4.600. for I also havent figured out the stroke yet....
    What should I be looking for in heads? port size etc?
     
  6. G72Zed

    G72Zed Veteran Member

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    You need to decide what the target HP is, and at what RPM range based on what you need to get out of this build. You have to decide if an "over or under" squared build works for you and in your favor with the power adder of choice, once you decide. You can't pick the proper heads until that's decided, lot's of choices, and that makes it easy to make a mistake.

    Whatever you do, do not buy a new block and go "max" bore right of the hope, seen that before, and unless $$ is not a problem, that's not a good way of going about it.

    Question, what is your HP goals/needs, is it based on meeting a required ET, or just getting the most out of a build.
     
  7. mjoc

    mjoc Veteran Member

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    TO answer your questions, my target HP is 1000+hp with the ability to add more PSI later and get over 1300hp. I want to try and keep the redline around 6800-7200 rpm.
    Im not looking for for an ET.. I just want a very very strong motor that Most people wouldnt be able to get even close to me....
     
  8. G72Zed

    G72Zed Veteran Member

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    Well, if your not 'hitting" an ET or competing in a form of motorsport that's easy enough with a well built BBC with boost in the 468- 540 range, lots of good heads out there to support that as well, looking at 7k+ rpm your in the solid roller territory, and lots of choices there, as well as custom grinds. Choice is yours, so many good combo's, maybe it will just come down to price and availability.

    So easy to build big power these days, it's crazy what's available....Good luck in your build.
     
  9. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    If you want to build this yourself - I get it. But if you've ever put an engine together before (no idea if you have) those levels of power building leave little room for error
    If you're going with a Dart Block (good idea) I'd suggest working with Carl Hinkson - he pops up here sometimes and offers pre-machined blocks.
    https://hinksonautomotive-cncblocks.com/products/

    With boost, if you're already doing an aftermarket block, I'd be tempted to do something like a 509 (4.5" bore x 4" stroke). The shorter stroke (well relatively, it's a 454 stroke) and the large bore is going to be very friendly to boost. Keeping the piston pin out of the ring-pack while having a big bore for a wide-open valve path. The engine is going to make more torque than any tire can absorb, so giving up some theoretical stroke of say a 540 is worth it.

    Quick note here, 7000RPM for a Big Block is screamin'. When you're running strokes that long, the piston speed gets ridiculous. The 427 L88, which was the standard for road racing big blocks for a decade, was DONE by 6000RPM. Shoot lower, at 500cid with good turbo's you'll easily be over 1000HP

    Another note, and should be clear on this from the start: You are going to have $25K-$30K into this engine with the EFI and supercharger. Figure another $4000-5000 for a transmission that will actually survive this engine
     
  10. mjoc

    mjoc Veteran Member

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    Thank you for the info.. Ive built a few small blocks and the 420ci sb blown motor in my camaro was pretty much built by me with some help from a few friends. Im also very very meticulous so Im not worried to much..
    THe trans mission Ive looked into building would be cheap if I could find it for $5000. I plan on having a small fortune into this project....
     

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