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Big Block Questions

Discussion in 'The Garage' started by Z3PR, Apr 1, 2003.

  1. Z3PR

    Z3PR Banned

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    I've built lots of SBC's, but the big blocks I've owned were either stock, or already built when I got them. Is there any different thinking when building a Big Block verses building a small block ??? How high of compression on pump gas ??? With the SBC, I could go 10.2 to 1 on 91 octain aslong as everything was tuned right. Normally I built them for 9.8 to 1. Would 9.6 to 1 be okay in a big block ??? What about head ??? Sence torque is the goal, would I want ovel ports or square ??? Any tricks with the rods ??? Any prefered pistons ??? Any advice on building a big block Chevy ???
     
  2. Z3PR

    Z3PR Banned

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    ttt
     
  3. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

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    If your going for low end tourqe use oval port heads /forums/images/graemlins/truck.gif
     
  4. ratlover

    ratlover 1/2 ton status

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    Definatly go with oval ports, there are alot of good factory castings as well as good aftermarket ones. I would go with iron as apposed to Al.

    Dynamic compression is the important thing to look at when trying to see if something will like pump gas or not. Static means nothing. But this is the exact same with a BBC as a SBC.

    SBC's act like a BBC in relation to compression and pump gas. Just about everything applies, if you are good at building SBC's then its an easy transition. Things that affect detonation are the same. Chamber design and proper tune and how a cams selection can alter things are pretty much the same when dealing with the 2 motors. Cams just are bigger for a BBC. Polishing your pistons and removing heat risers work the same in a BBC as a SBC and all those other types of tricks. One thing that is critical for running a motor on the ragged edge of compression and building an efficent powerfull motor is proper quench. This is as important in a SBC as a BBCand the way you change it are the same.

    About the only difference between the 2 in regards to compression is that generally a BBC requires more dome to get higher compression. Try to run a small closed chamber head to keep a smaller or no dome for better flame travel and still keep adequate compression.

    What do you mean tricks with rods?

    A specific compression ratio is a bad thing to shoot for, you need to worry about the whole set up and what else you have to work with. I would say that 9.5 will be pretty high with a very tight cam with very little overlap but if you are running a mud bogger and going to spin it to 6 grand then you might need that big of cam and thus need that much compression.

    I generally like to run hypers, personal preference is basicly the same in SBC as BBC.

    Any other specific questions?
     
  5. fortcollinsram

    fortcollinsram 1/2 ton status

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    Oval heads will provide good torque and HP...small peanut pots (round ports) offer lots of lowend torque at the expense of HP...Rect. port head offer stupid amounts of high end HP, will nothing that even resembles torque down low...

    I personally like the hypereutectic pistons with the coated skirts...I second the FT pistons with the closed chamber head...9:1 --> 9.5:1 seems to make a pretty happy BBC...Same principles with rods apply..Stock BBC 454 rods are 6.135, most strokers use a 6.385" or longer... Oh BBC's are BIG AND HEAVY...that makes them fun to play with... /forums/images/graemlins/thumb.gif That is until you have to move the short block or long block around by yourself /forums/images/graemlins/angryfire.gif

    Chris
     
  6. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    What do you mean tricks with rods?

    [/ QUOTE ] Rod lenght.. I was looking in a Jeg's catalog at the Eagle Specility ESP rods and noticed different lenght rods. What about building a stroker big block ??? I will be buying steel rods and a steel crankshaft. So shoot for 9.0 to 1 and 9.5 to 1 compression ??? I was thinking these heads , with this cam , and a Wiean Stealth intake manifold.
     
  7. fortcollinsram

    fortcollinsram 1/2 ton status

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    Personally, I would go with a cam that has a bit more duration and lift...I don't think that cam will take full advantage of the flow that those heads offer... /forums/images/graemlins/thumb.gif If you wanna steick with case iron heads, those merlins are some of my Favs..if you Alumin. go like Edel 6045 or similar...

    Chris

    Hit up www.454ss.com and gnaw on RF's brain a bit about head selection...dude know his shiznit... /forums/images/graemlins/thumb.gif
     
  8. Z3PR

    Z3PR Banned

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    So you think alittle more cam, huh ??? Okay, I won't complain about that, lol. What would you recomend using the Comp Cams Xtream 4X4 series cam. ??
     
  9. fortcollinsram

    fortcollinsram 1/2 ton status

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    If you wanna stick with the Xtream 4x4 cams, check out the X4270H grind (comp P/N 11-239-3)...It all depends on where you want the engine to make power...If you wan't more lowend torque go with the cam you mentioned above..but those heads are very capable of flowing some air so why not take advantage of that an get a little higher lift cam?

    Personally, on my next BBC build I am going to be using the Edel 6045 heads with the Comp XR276HR grind cam (Hyd. Roller)...Pretty much the same setup Shawn has and it absolutely hauls..
     

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