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400 SB question

Discussion in 'The Garage' started by hidesertwheelin, Nov 19, 2004.

  1. hidesertwheelin

    hidesertwheelin 1/2 ton status Premium Member

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    I have a 400 SB in my blazer on it's last leg. Should I rebuild it or just get a 350 SB. I keep hearing horror stories abount the 400 SB. What is needed to make the 400 a good engine? I already have a 4-core radiator. Beside the basic things you do when rebuilding a engine is there anything specific that needs to be done on the 400? /forums/images/graemlins/confused.gif
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Quality machine work , attention to detail , good radiator , make sure heads have steam holes , as well as the head gaskets have the holes ( 400's have siamesed cylinders ) . No worries . Build it right , take care of it right , and it will last a long time /forums/images/graemlins/waytogo.gif
     
  3. original balzer

    original balzer 1/2 ton status

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    me personaly i would build a 383 stroker they are getting resonably cheap to build and have good low end touque when built corectly but thats just me

    willow /forums/images/graemlins/peace.gif
     
  4. Z3PR

    Z3PR Banned

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    The 400 is a great engine as long as you don't over rev it. Not my first choice in a mud truck that see's alot of high RPM's. But if you're crawling or trail running, the 400 is a good motor. /forums/images/graemlins/thumb.gif
     
  5. diesel4me

    diesel4me 1 ton status Premium Member

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    I beat mine to death abd havent killed it yet!.The main weakness of the 400 SB is they dont take kindly to being overheated(though I have boiled mine over many times when I put the plow on,and didnt lock the fan clutch on! /forums/images/graemlins/blush.gif),usually they will crack between the siamesed bores if you get them too hot.Other than that,they are a very strong running motor--but like a 454,its long stroke doesnt make it fond of high RPM's--but you can swap different cranks into it to let it rev higher if thats what you want--but you'll lose a lot of tourque.I like mine just the way it is--it replaced a noisy 454 I had,and the power is about the same,and its 200lbs lighter!. /forums/images/graemlins/crazy.gif
     
  6. SUBFAN

    SUBFAN 1/2 ton status

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    Keep the 400....If you can't have the downtime to build the 400 and reinstall, I would look for a later model roller block and 1 piece rear main seal. Stroke it and take advantage of installing a roller cam hella-cheaper.
     
  7. rodzzilla

    rodzzilla 1/2 ton status

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    Another weak spot is the connecting rods. They are shorter than other small blocks (5.56 as opposed to 5.7) They use shorter rod bolts to help clear the cam shaft. Either gring the bolt heads down, or get a smaller base lobe cam.

    Keep it and have a great torque engine. /forums/images/graemlins/thumb.gif
     
  8. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    What is needed to make the 400 a good engine? I already have a 4-core radiator.

    [/ QUOTE ]Nothing at all! It is already a great engine. It is just slightly different than ALL the other small blocks and some people don't understand them, remember, when people don't understand something it usually gets a bad rep. easily. They need a 4 core radiator because of the siemease cylinders and can't get away with a 2 core like every other SBC. The heads are different and don't swap with anything unlike every other SBC. When people try and use other SBC parts like heads on a 400 the results are disasterous and the bad part is when something gets a bad reputation, it usually can never shake it's rep. I love my 406, there is a HUGE difference in power from it and my old stock 350. The great part with a 400 is that they make low end torque like a big block but can still wind up just like a small block. I guess they are a little slower winding up than a 350 but mine sees 5500 RPM's all the time without a problem and can wind up faster than my old 350 IIRC. My blazer with 35's and 4.10's will out pull my '76 C30 with a 454, 31's and 4.10's.
    I think the stock numbers are 205/335 on the 454 and my 406 is about 315/400. /forums/images/graemlins/thinking.gif If you plan on building it up for some power don't make the same mistake I did which was to spend money porting the stock heads. Just buy a set of Merlin torquers or Pro top lines, any aftermarket head designed for performance is going to vastly out flow the stock 400 heads. Just make sure you order them for a 400 with steam holes. /forums/images/graemlins/wink.gif It is vastly important to go with a bigger head on a 400 because of their size. The stock heads work great on a 305 but that same size head on a 400 doesn't cut it. Stay away from a lot of compression, 400's don't like high compression because of the heat generated from the seimease cylinders.
    If yours is a complete original 400 than tear it down and do your standard SBC rebuild with bearings machining, and gaskets. Keep the 400 rods, they are different than other SBC rods. Go .030 boring to make it a 406, no bigger or you will have overheating problems.
     
  9. SUBFAN

    SUBFAN 1/2 ton status

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    The heads can interchange if you drill/fill the steam holes.

    My 400 was bored .040 over with no overheating issues....

    World Products S/R Torquers....

    I like to install 5.7" rods to reduce the side loading on the cylinder walls....
     
  10. 3 on the tree

    3 on the tree 1/2 ton status

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    Back in the early 80's I was involved in dirt track racing. Most of the guys I knew ran 400 small blocks.They would typically turn 6000-6500 rpm with few problems.Polish and balance the rods, go with GOOD rodbolts,Light pistons and they will rev and stay together just fine. Stay away from the factory 4 bolt main motors-the webs are actually thinner than the 2 bolt main blocks.
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    The heads can interchange if you drill/fill the steam holes.

    [/ QUOTE ]

    No need to fill if using 400 heads on a 350...simply use the 350 head gasket. /forums/images/graemlins/thumb.gif
     
  12. Triaged

    Triaged 1/2 ton status

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    If you do want to get rid of the 400 I'll buy it off you... /forums/images/graemlins/whistling.gif
     

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