540 BBC swap '73 split bumper

Discussion in 'High Performance Modifications' started by RollzRoyce, Dec 17, 2017.

  1. RollzRoyce

    RollzRoyce Member

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    Aug 19, 2017
    Hi y'all.

    I picked up a '73 Z28 clone in March and while I like the 357ci SBC that is in it I just kinda need more power, you know... Everyone is doing the LS swap + turbo thing but I wanna keep it old school, screw that. In 20 years people might be putting laser fired engines in these things but a big block or small block will always be correct. And I just love the look and sound of the old engines. I was on the fence for a bit on SBC vs BBC but decided to go big and not look back. I bought/traded for a Gen VI 540 BBC short block with Wiseco 14.5cc dome pistons, scat procomp I beam rods w/arp 8740 bolts, a ohio crankshaft 4340 crank, king rod & main bearings and total seal rings. My drive train is already built for big block power (built 4L80 w/reverse pattern manual valve body & lots of billet parts, Circle D 3000-3200 stall convertor, rear end is just a 8.5" 10 bolt with yukon axle parts but it is built to handle approx 950whp, 3.73:1, drive shafts and u-joints are good to go, 275/60r15 Nitto drag radials...).

    Like I said I need that big block power/torque but I also want it to be reliable/streetable and low maintenance. I would like it to last a while and I want to be able to drive it on the freeway. I am just building a fun street machine, no track dreams, my only real goal is to be able to spank 9 out of 10 new mustangs and send them runnin for mommy, "go get a bigger turbo!!" ha. So I'm gonna go with a hydraulic roller, keep the compression in the 10:5-11:1 range to run on 93 octane (eventually convert to E85 though) and not cam the shit outta it to put eloquently, but I still want a healthy lope. I am having it built by a quality builder in Houston but he is used to doing more max effort builds so I kinda wanted to run what I/we had in mind by y'all and see what y'all thought, if it was good for my setup. I am looking for approx 700+hp and 675+tq (or more of course) and a nice flat torque curve that comes on strong around 3000-3500 and lasts until about 6k, not too concerned about revving much beyond that. I want great throttle response and brutal torque, not worried about peak numbers. I am not going cheap on this build but don't want to break the bank either. I picked up the short block for about $4k with trade value and would like to keep the total to around $11-12k.

    I think I am going to go with the 325cc rectangular port AFR heads set up for a hydraulic roller. They seem like a good deal for what you get, cost is an issue so I don't really want to spring for the 315s but I think I will opt for the fully CNC'ed chambers for the extra $214, the chambers are 121cc when fully cnc'd which would put me right about 10.5:1 (117cc for partial, 10.7:1 or so). I also really like the 300cc oval ports and think they would probably work well for my application but they are a bit more and the 325s will probably get me where I need and leave room for future full port work. Thoughts on that? I also looked at the Promaxx Maxx 317 BBC heads as they look to flow awesome out of the box but I think I really want to spend a bit more and get AFR heads. I gotta say, I guess I just kinda want them, lol. And while I know the Promaxx are pretty quality for Chinese I would rather keep as many American parts as possible, it's a piece of Americana muscle, you know.

    For the cam I am looking at the extreme energy Comp cams, the xr294hr (01-424-8, 242/248 @ .050, .540"/.560") and the xr300hr (01-425-8, 248/254 @ .050, .560"/.580"). This is where I could really use some suggestion. The xr300hr says it calls for a 3500+ stall and I am only at 3000-3200, but with the fairly premium heads I am getting and 540ci would my setup be able to utilize it properly? I would rather get the extra duration and lift of the xr300hr but not if it would not work as well for what I want to do. I'm going to run comp magnum ultra 1.8 roller rockers.

    For the intake and carb we are thinking a super victor and a Holley 1150-1250.

    Any suggestions on headers? I was going to run 3.5" dual exhaust with an x-pipe I think.

    What do y'all think, am I headed in the right direction? Sorry for the long winded post, trying to give enough info, thanks for reading. Let me know if more info is needed. Car is about 3400# or so.

    Royce
     

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    Last edited: Dec 17, 2017
  2. Blown Camaro

    Blown Camaro Veteran Member

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    Dec 13, 2009
    Deltona, FL
    Interesting.

    Subscribed!
     
  3. Turbo70Camaro

    Turbo70Camaro Veteran Member Gold Member

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    Jan 7, 2005
    so cal
  4. RollzRoyce

    RollzRoyce Member

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    Aug 19, 2017
    Ok, yeah this is good advice. This is what my builder was initially going to do but then, just for shits n giggles really, I thought we should at least look into the extreme hydraulic cams they already make. We saw the recommended 10.5:1 compression, 3000 (on the 294) & 3500 (on the 300) stall, etc., and thought it seemed pretty fitting for my build. But I hear you, I guess one of those cams would be fine but likely not optimal.
     
  5. 77 cruiser

    77 cruiser Veteran Member

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    Nov 17, 2006
    Frostbite Falls MN
  6. 1980RS

    1980RS Veteran Member

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    Jun 17, 2006
    MN
    I read on a site that someone used an Air Gap with a 1000 cfm carb on a 540 and made over 750hp with it. that would roast your tires nicely and keep it under the hood better. With an engine like that you could run mid to high 10's with a 3.08 gear in the car.
     
  7. RollzRoyce

    RollzRoyce Member

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    Aug 19, 2017
    Ok, yeah I have heard & read really good things about him. I do need to call him.
     
  8. RollzRoyce

    RollzRoyce Member

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    Aug 19, 2017
    While I do think clearance is going to be somewhat of an issue, my builder strongly recommended a well-flowing single plane and a dominator flange for 540ci. That said I hear you, I prolly could make the power I want with an air gap and a 1000cfm but I kinda want to let him "build it" so to speak and not just throw him a bunch of parts. Don't want to neuter him too much. He is pretty good. I think I will just go big and go for the super and dominator, he's already kinda sad I'm not doing a max effort. Ha. I know it's my engine and I can do what I want but I also know that I'll likely get used to the power. I think my torque curve should be pretty good with the moderate duration & head size and 540 cubes, I think I can pull off what I want with a single plane. If it'll fit under my 2" cowl though, I hear ya!

    Does anyone know about how much higher a BBC block sits than a SBC? Without factoring in the difference in intake manifold height. About an inch or two? Or more?
     
  9. 1980RS

    1980RS Veteran Member

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    Jun 17, 2006
    MN
    There was an intake that Edelbrock made years ago that you should be able to find it is a C-454X or a Torker 4500. Both are dual plane intakes that should fit under the hood well. There is a guy who races at the local track that has that intake and a 1050 dominator in a 72 Corvette with a 505, he runs 10 flat @ 132 with it. It's funny as when the hood is open it looks like a stocker until you look closer at the engine. Most you will is a little mph with that intake over a single plane, but with a 540 I don't think you will notice it on the street.
     
  10. RollzRoyce

    RollzRoyce Member

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    Aug 19, 2017
    Ok cool. I will look into those, thanks for the tips.
     

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