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Thread: first time building a 400 SBC

  1. #1
    Member JOURNEYMAN
    Join Date
    Jan 2008
    Location
    Newcomerstown, OH
    Posts
    33

    first time building a 400 SBC

    I have built a couple 350's, now I am wanting to join the 400 club now.

    What are some do's and don'ts? It will be a drag motor in a tubbed 72 chevelle. I would like to get high 10's out of it on motor in the 1/4, I mostly run 1/8th mile though.

    With the steam holes...should I plug them on the deck or just slap some heads and gaskets on it and forget about them?

    I will be using a GM block...what should I look for in the blocks? Weak spots?

    How strong are the stock cranks? I would like to spray 100-150hp of nitrous.

    Thanks for all the input,

    Travis

  2. #2
    Senior Member RACING JUNKIE
    Join Date
    Sep 2007
    Posts
    4,143
    The crank won't be your problem it will be the block. The 2 bolts are stronger but they are all questionable. Do a search on here and SPEEDTALK there is a lot of info. As far as the steam holes I always just drilled them in the heads I was gona use...but I only messed with 400 sb in a street /strip application. I've built 2 of em with factory blocks but compression was never over 11 to 1 and power was 500 or less I'm sure...also was a 72 Chevelle.

    http://forums.racingjunk.com/viewtop...er=asc&start=0

  3. #3
    Senior Member EXPERT BUILDER
    Join Date
    Aug 2005
    Location
    Tell City, IN
    Posts
    356
    The block to look for is a "509" Casting and a 2 bolt. You could splay the center mains if you want for added strength. If you are going to stay with a 406ci and plan to keep the RPM's down around 6000.. (6200Max)
    You should be fine with the 2-bolt. I would try to get at least a Cast Steel crankshaft and make sure to have it all balanced. If you want more RPM or Nitrous you should at least splay the main caps or get one of them new Dart SHP blocks. These are just my opinions. I have a 509 casting was a 2 bolt block now a splayed block and it is 422ci. It is all 4340 and Internally balanced and I run it up to 6800 or so.
    Your luck may very though.. 8)

  4. #4
    Senior Member MASTER BUILDER
    Join Date
    Oct 2007
    Location
    Staunton,VA.
    Posts
    249

    for the 400 1st timer

    I agree 2bolt 400 blk.s are definitely stronger, the crank's are weak usually break somewhere in the vecinity of the center saddle/cap. Big main journal's 2.650" , heavy c.weight's,less rpm, w/ a stock crank, maybe 6200. 3.750" stroke is nice, 4.00" stroke is better, just splay the main's. By the time you bore, align,splay,&clearance you got the cost of a new block anyway or close to it. I run a 2bolt w/ a 3.48" stroke stock crank w/ stock rod's, KB piston's, balanced. Work's great, spins to 7200 easy. Have spacer's in the block carries 40psi @ 190degrees temp. on 110 gas. Been together 4 yrs. now, getting ready to tear down for 1st time since built it. With MORE stroke you turn less rev's for more power/efficiecy. that the goal anyway.

  5. #5
    Senior Member RACING JUNKIE curtisreed's Avatar
    Join Date
    Feb 2004
    Location
    KIEFER, OK.
    Posts
    1,309
    As has been stated the block is where you have to center most of your attention. We have a 509 block w/splayed caps. Everything else is just basic small block stuff you have to do to make power on any stock block. Our 406 made 720hp. When you start making big power you will find that it is hard to keep any stock block stable. Blowby, oil leaks, comes with the territory if you don't have a vacuum pump.

    Curtis

  6. #6
    Senior Member MASTER BUILDER
    Join Date
    Oct 2007
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    Staunton,VA.
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    249

    1st time 400

    doorracer, ever used an electric vacuum pump?

  7. #7
    Senior Member RACING JUNKIE curtisreed's Avatar
    Join Date
    Feb 2004
    Location
    KIEFER, OK.
    Posts
    1,309
    I bought a couple of different styles but neither showed much promise so we didn't even bother trying to hook them up. I got a really good deal on a Mr. Gasket recently, $250.00 w/bracket, pulleys and fittings brand new. They were on here and in the back of ND.

    Curtis


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