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400 sbc

Discussion in 'The Garage' started by blazin_blazer, Mar 19, 2007.

  1. blazin_blazer

    blazin_blazer 1/2 ton status

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    i have a 400 sbc that i recently acquired, upon teardown i found it has been bored .040. my question is will the 400 sbc handle a .060 overbore or should i try to get by with just honing it? also the crank has to much end play, will new bearings cure it or is a new crank needed to tighten up this end play or is it possible it could be the block? , but it seems really excesive.
     
  2. 1977k5

    1977k5 3/4 ton status Vendor

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    I wouldn't bore it any more and don't know what to tell you about the end play :dunno:
     
  3. superwrench

    superwrench Registered Member

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    Some guys dont want to run them bored at +.060. I have not had any problems out of the one I built for a friend. One suggestion is to keep the compression down if your going to use it as a daily driver. His has around 8.3 and runs around 220 on hot days pulling a load. The crank shaft end play can be fixed by an over sized thrust bearing. But the crank needs ground to take the ruff edges off it( the thrust) rods and mains need ground anyways. I would just get a different crank, by the time you get that one done you can buy a aftermarket one. I build alot of +060 400 blocks for the racers around here, If you dont want to use it what do you want for it?? I might be interested.
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    400's are prone to over heating so i would not go .060" without first sonic testing the block to check for cylinder wall thickness.

    400's are also prone to cracking in the lifter valley so i would mag the block in that area first.

    The end play issue is easily fixed in one of two ways. You can either have the thrust on the crank welded then ground back to the proper size or you can have the thrust on the crank opened up to use the wider thrust bearing that was made for this purpose. It would probably be cheaper and a better idea to buy a new crank though as you'll end up with a far superior crank over the stock crank.
     
  5. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I'd be worried about .040" overbore. IIRC, back when I was building my 400, .030 was as much as you wanted to go on a daily driven type 400. 40 and 60 was fine for racing, IIRC.
     
  6. blazin_blazer

    blazin_blazer 1/2 ton status

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    thanks for the replies....looks like a honeing and a new balanced rotating assembly then.....maybe use the oem crank in a spare 350 block, if they make the bearings for the 350 to cure the end play.
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If you're going to buy a rotating assembly don't even waste your time keeping the old crank, the mains need to have .200" machined off in order for it to fit into a 350 block and the difference in price of having that done along with a grind versus buying a stroker crank when the time comes it would be cheaper to buy the stroker crank.
     
  8. super k

    super k 1/2 ton status

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    I`d never bore a 400 unless it`s needed.You didn`t say why you would want to bore.It`s rare for a small block top need it.
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    You better go back and do some research. When an engine starts to get alot of miles on it the cylinders become out of round and have lots of taper in them and require to be bored. A 400 chevy has the compouded problem of a very short rod to stroke ratio which side loads the cylinder walls and accelerates the wear.
     
  10. super k

    super k 1/2 ton status

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    I know all I need to know about the 400 after building as many as I have,from standard bore to 406s to 427s.As I said,he never said why he wanted to bore it.What that means is we don`t know that it has many miles on the last build when it was bored .40 over.Maybe it was just rebuilt and the end-play wasn`t addressed.And,maybe there were not enough miles after the build to affect the cylinders.He also didn`t mention the cylinders were out of round,tapered,or any other mic`d results.I guess you could say I was suggesting more "research" was needed before considering boring.It`s"NOT"always required and "I" never do it unless necessary,especially on a block that is getting harder to locate.
    Are you always this assumptive?Or,is it just with people with few posts?I`ve been building 4wds since way before I ever knew what a computer was.My`72 K/20 turned K/30 runs a 406 that I built.It was already cut to a 406 for a drag car.I tore it down and re-cammed it for my truck and thoroughly inspected all wear surfaces and found no machining was required.I had it micro-polished(they agreed it needed no machining after their check)and balanced.I brought the block and had them double check and they sent me home with it.I honed it and it`s one of the healthiest motors you`d ever seen.
    Research?Get to know someone before you attempt to come down on him.He may just know his stuff,like me.
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    As far as me being "assumptive" I was more directing it towards the hi-lighted reply you left at the end.

    Now, maybe you have or maybe you haven't read my profile and found out that i'm an automotive machinist for the last 20 years and have plenty of experience with what i say.

    Your low post count doesn't mean anything to me. There are people on here that hardly ever post that know their sh*t and there are also people on here that have a very high post count that don't know sh*t.

    With that being said i hope you understand that i wasn't trying to bag on you but only wanted to make sure you know the remark about "it's rare for a small block to need it" was a fairly inaccurate statement especially with the short rod and long stroke of a 400. :deal: :)
     
  12. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    I'm no machinist but, in my 30 years, 6 of my 9 rebuilds have "required" that the cylinders be bored to achieve good ring sealing. I've tried to "get by" with a hone a few times, and its a oil user at best.

    Just my observations.
     
  13. super k

    super k 1/2 ton status

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    Ok,we`re cool.The go back and do the research comment rubbed me wrong.I hadn`t checked your profile,either.I`ve been lucky enough in my builds to come across mostly good bottoms and worn top ends...really.I always have my stuff checked for backup judgement when I get it cooked,anyway.This guy gave no info on condition,just asking about boring more.We can assume it was tapered,had a ridge,heat damage,etc.But,I saw it like he just wanted to bore,regardless.My present 400(406)was raced and,yeah,it needed full treatment.But,I`ve pulled them from old wagons,etc. and they were beautiful inside.
     
  14. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Cool, glad we worked it out. :D

    I'm not saying that all engines need to be bored either. I would only bore an engine if needed as well. Why remove life from an engine if you don't need to.
     

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