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Small Block 400 - Any thoughts??

Discussion in 'The Garage' started by mikeperez22, Jun 16, 2004.

  1. mikeperez22

    mikeperez22 Registered Member

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    I have a 72 and it came with the original 350 and a complete 400 that is not installed. Any thoughts on the 400. I have been told that the 400s have some crank issues. I'm trying to decide if I should rebuild the 350, drop in the 400, or just sell them both and buy a crate engine. Any thoughts on the 400?
     
  2. Z3PR

    Z3PR Banned

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    I have a 400 small block in my 76 K5 and like it alot. If I had the $$$ I'd like to get the 415 stroker kit for the 400. If you're worried about a crankshaft (Never heard that one befor) the stroker kit replaces the crank anyways. /forums/images/graemlins/thinking.gif
     
  3. Poohbair

    Poohbair 1/2 ton status

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    I have owned 2 400's and never had trouble w/ them. I understand that in a 400 you want a 2bolt block, not a 4 bolt...because on a 4 bolt the outer bolts are too close to the edge of the block or main cap and usually cause cracks...especially if you turn high rpm's.
     
  4. 75-K5

    75-K5 3/4 ton status

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    400=good /forums/images/graemlins/thumb.gif

    I have a 400 sitting in the bed of my pickup right now. Soon it will go to the machine shop to get all that out of the way, then it's 415 stroker time. /forums/images/graemlins/weld.gif
     
  5. Hustler

    Hustler 1/2 ton status

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    Go with the 400. The only problem I have heard about them and that I myself have had is they will run hotter then a 350. Other then that, they have much more low end torque then a 350.
     
  6. surpip

    surpip 1 ton status

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    mix the 2 400 crank 350 block, got your self a 383 stroker and no thin walls between cylinders= no cracked block
     
  7. 75-K5

    75-K5 3/4 ton status

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    415 > 383 /forums/images/graemlins/waytogo.gif
     
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    If 400 SB cranks are weak,you cant prove it by mine--it has low oil pressure,I dont change the oil as often as I should,has well over 100,000 miles,and it gets a good beating everytime I plow or haul heavy loads with it---and it doesnt even tap or tick on a dry start after sitting for days.If it were weak I'd have a rap by now!.
    The only weak spot in a 400 is the block,due to the fact the bore is so large there is no room for cooling passages between the center cylinders.I have overheated mine several times badly when I forgot to lock my fan clutch in,and drove several miles to plow my customers driveways,and so far I havent even blown a head gasket! /forums/images/graemlins/blush.gif This motor was from a 78 suburban that towed big boats,and was used to commute to boston at 75 mph for several years--when I bought the truck I needed the motor in my truck quick,I threw it in without even changing the timing chain or oil pump,heck I didnt even wash it! I cant complain about it,thats for sure-I do sometimes wish I hadnt been so hasty and put in a new timing chain and gears,cam,lifters,rings etc,but the truck is pretty rotted now,so it might be a project to rebuild it for another truck--I was thinking of putting it in my 79 C10--less work than the caddy motor conversion. /forums/images/graemlins/thinking.gif
     
  9. djsblaze

    djsblaze 1/2 ton status

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    I had an original bone-stock 400 in my old 78 K5. Dont know how many miles were on it, but I would presume alot, it was a rough old truck. Outside of running a little hotter than a 350, I never had ANY trouble out of it.
     
  10. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    As long as whatever heads you use have the "Steam Holes" needed for a 400 , you should have NO problems at all with regular maintainence and good work during build /forums/images/graemlins/k5.gif
     
  11. crazyrc

    crazyrc 1/2 ton status

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    I love my 406 SB. Other than torque below 2400 RPM I would put it up against most any big block. Not to say its better than a big block, just very competitive and lighter.
    460 H.P. @ 5600 /forums/images/graemlins/grin.gif
    540lbs @ 4400 /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
    380lbs @ 2800 /forums/images/graemlins/peace.gif
    I highly recomend Comp cams 4x4 Extreme roller cam. I went with the "lumpiest" of the three availble profiles, but I play in mostly in the mud and it still idles fine.
     
  12. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I have a built 406 and it is a tough motor. THey wind up almost as well as a 350, better than a 383 and make more HP.
    Building tips for a 400 block:
    1. WATCH YOUR COMPRESSION! You can't run as much compression as a 350 because of the siemease cylinders.
    2 Don't bore it past .030" and make sure the heads have steam holes.
    3. Use a 2 bolt block if you can and if it is crazy enough...just use splayed main caps.

    I have been plagued with pinging with an overall comp ratio of 9.2:1, iron 76cc heads, and Chevron 91 octane. If it gets warm it pings. I have been fighting my running temperature almost since I put mine in, I can't seem to make it run much under 200 degrees in moderate spring time weather and I have to stare at the guage like a hawk on hot summer days to the point where I can't drive it currently in stop and go 95*+ weather...and I can forget about running the A/C at times. /forums/images/graemlins/mad.gif I am going to buy the monster dual 15" flex a lite truck fans and combined with my current new 4 core rad hopefully I can keep the temp under control. Don't let me discourage you, it's a badass small block! They can take a lot and I have had mine up to 260* on several occassions and havent had a problem with it.
    A good original bore 400 block is worth a fair amount of money also and will only increase in value because of their rarity.

    I say build the 400! 350's are BORING... and 383's are too expensive. /forums/images/graemlins/thumb.gif

    Oh and a 415 is nothing...I have seen a stroked 400 to 434ci. /forums/images/graemlins/pimp1.gif
     
  13. fortcollinsram

    fortcollinsram 1/2 ton status

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    The guy that built my BBC just got done building a 400SBC that is MEAN.

    -Dart Little M block
    -Scat crank and rods (forged)
    -Ross FT pistons
    -Edelbrock Performer RPM head that have been ported a bit
    -full Comp roller valve train with 1.7 ratio rockers
    can't remember the specs on the cam but it is a very streetable cam...medium duration with a higher lift...

    On the dyno, it made 512hp can't remember the tq but it was up there too with a nice flat curve...

    it is a MEAN motor..

    Chris
     
  14. 1979jimmy350

    1979jimmy350 1/2 ton status

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  15. fortcollinsram

    fortcollinsram 1/2 ton status

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    [ QUOTE ]
    I love my 406 SB. Other than torque below 2400 RPM I would put it up against most any big block. Not to say its better than a big block, just very competitive and lighter.


    [/ QUOTE ]

    I bet my BBC will be the same as your SBC in about 2 weeks /forums/images/graemlins/whistling.gif I ahve Edelbrock Performer RPM aluminum heads, and aluminum intake ready to put on The heads are 40# lighter a peice than the stock heads and the intake is 30# lighter. that is a 110# lighter and another good bit of horsepower /forums/images/graemlins/woot.gif /forums/images/graemlins/woot.gif
     
  16. 350350

    350350 1/2 ton status

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    I've had a lot of 350's and a lot of 400's. As others have stated, the 400 will run a little hotter, but in a K5, you've got massive room for an adequate radiator, so this shouldn't be an issue.

    A good example is the first 400 I rebuilt. I rebuilt it with a stock bottom end, 0.030 over (406), 1.94 heads, and then the biggest cam I could run with stock valve geometry.

    I dropped it into my '78 Malibu with a 700R4 and 3.42 Posi, 16x8" wheels with Gatorbacks, and was undefeated in town. Most competitors were running 'built' 350's with aluminum heads, full roller rockers and cams, etc. They were constantly in awe that my stock iron heads and extra 50ci could whomp them.

    Think about the increase in performance you get when you yank a 305 and drop in a 350... 50ci makes a BIG difference in and of itself. When you add mods to that 50ci, you get an even bigger bang for your buck...

    Just for grins, I'd like to do a 396. I've done a 383 and see no reason to do another one compared to a 406. But the 396 stroker is getting close enough to the 406 in cubes that it might have some value...

    Then there's the whole discussion about rod length, which I would recommend at least 5.7" rods in ANY small block (350 rods) and depending on your intended use probably 6" rods. There's complicated arguments on TDC dwell and the amount of pressure the side of the bore takes from the rod as it comes around on the upstroke, etc. The stock 400 has something like 5.4" rods, and tend to push the piston through the side of the block when turned high rpm's... Depending on your application of course!

    OK, enough of that babble. 400+ cubes or more. Play it safe. /forums/images/graemlins/peace.gif

    Paul 'X' /forums/images/graemlins/thinking.gif
     

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