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Which is a stronger setup?

Discussion in 'The Garage' started by thefarside, Jan 15, 2004.

  1. thefarside

    thefarside 1/2 ton status

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    I was chatting with my brother the other day and he was talking about engines. We started to debate which was stonger setup, a four bolt main block or a two bolt with splayed caps. I said the two bolt with the splayed cab was stronger than the four bolt. I was wondering who was right? /forums/images/graemlins/confused.gif

    Also, a 383 stoker is a 350 with a 400 crank and rods that has had some machining done correct?

    Odd question, what is magnaflux checking and how does it work? Is it worth the 100 buck a part to have them check?
     
  2. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    From what I've read, a 2-bolt block that's been modified to a 4-bolt splayed setup will be stronger than a factory 4-bolt block. The reason is that the factory setup has all the bolts going straight down which offers less ultimate strength.

    On the flip side, I don't know what it costs to retrofit a 2-bolt block to a splayed 4-bolt....it may be expensive enough that it scares people away.



    /forums/images/graemlins/thinking.gif
     
  3. lt61173

    lt61173 1/2 ton status

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    there were 4 bolt blocks that had splayed bolt patterns, they were factory setup. they are the best block. I have no idea what years. The outer bolts are splayed and the inners are strait down.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    It used to be that 4 bolts were the best, then the splaying idea came about, and it was best, and now some of what I'm hearing is that splaying ISN'T better necesarily than say a "standard" 2 or 4 bolt.

    Apparently, by running the bolts down into the webs, you weaken that area, (which is thinner than the bearing cap/normal bolt surface IIRC) which allows movement, which is obviously a bad thing.

    I'd like to know exactly what GM was thinking with the 2 vs. 4 bolt applications...they would use 4 bolts in high powered car apps, but also in "HD" (many truck) applications. I've never seen anything that says why they thought that was any better, nor have I really seen any studies that was looking right at that area as to why whatever setup is best.

    As I understand it, the newer GM motors use 6 bolt caps, 4 from underneath, and 2 from the side. THAT makes sense, but again, they are using 4 bolts underneath. Perhaps it is to keep the bearing cap as straight as possible...with one bolt, the cap could possibly "twist" around the bolt I suspect.
     
  5. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    For your question on MAGNAFLUXING. This is a process where they put a dust of material on the parts that when they hover their tool over it it shows any cracks in parts. I believe the tool is just an electromagnet and it removes all but what sticks in the cracks. Saw them do it years ago on some heads I was given. /forums/images/graemlins/k5.gif
     
  6. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I am with Dorian... I know 400 blocks have problems with cracked webbing on 4 bolt main blocks. I have a 2bolt main 400 and I wish I would have done the splayed side bolts.
    And yes a 383 is what you described.
     
  7. TopOff

    TopOff 1/2 ton status

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    I thought the rods and pistons were different in a 400 SBC. I thought the rods in a true 400 SBC are 5.3" instead of 5.7 rods. I know you can run the 5.3 rods, but supposedly the 5.7 rods offer better power and better service to the bores due to less angle on the stroke. I also thought the 400 SBC pistons have a different wrist pin height because of the different rods.

    Additionally a 400 Crank needs to be turned down on the mains so it will fit in a 350 block. These days you can find a few manufacturers offering 400 strokes with a 350 mains for less money than finding a 400 crank and turning it down.

    The 350 Small block needs to be clearanced for the stroke sometimes at the oil pan and bores, and always at the underside of the lifter valley.

    I had 383. For the money in machine work, I found a 396!

    Have fun!
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    A 383 is commonly done three ways:

    3.75 stroke crank, 5.565" (400) rods, 350 pistons
    3.75 stroke crank, 5.7" (350) rods, custom stroker pistons (most common these days)
    3.75 stroke crank, 6" aftermarket sized rods, custom stroker pistons (for serious high performance applications)

    edited to fix stupidity
     
  9. R72K5

    R72K5 Banned

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    plus factory 4 bolt blocks are not technically totally 4 bolt, two of the caps on them are 2 bolt hah, and yeah splayed is the way to go if youre after strength if you think you might actually break a straight bolt cap, it would take one heck of a lot of power to do such a thing though, if you had thhat much power in a rig i would think you would end up with alot of broken things before you would end up with bropken caps.
    shafts,tranny, mounts, case, axles, etc.
     
  10. TopOff

    TopOff 1/2 ton status

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    Re: Which is a stronger setup? *DELETED* *DELETED*

    Post deleted by TopOff
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Wrong post there buddy.
     
  12. Beast388

    Beast388 1/2 ton status

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    [ QUOTE ]
    A 400 is commonly done three ways:

    3.75 stroke crank, 5.565" (400) rods, 350 pistons
    3.75 stroke crank, 5.7" (350) rods, custom stroker pistons (most common these days)
    3.75 stroke crank, 6" aftermarket sized rods, custom stroker pistons (for serious high performance applications)

    [/ QUOTE ]
    /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/rolleyes.gif

    Are you refering to a 383 or a 400? /forums/images/graemlins/thinking.gif
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Oops yeah, 383. 350 pistons in a 400 would be quite funny. Just a little bit too much piston to wall clearance. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
     
  14. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    I thought the rods and pistons were different in a 400 SBC. I thought the rods in a true 400 SBC are 5.3" instead of 5.7 rods. I know you can run the 5.3 rods, but supposedly the 5.7 rods offer better power and better service to the bores due to less angle on the stroke. I also thought the 400 SBC pistons have a different wrist pin height because of the different rods.

    Additionally a 400 Crank needs to be turned down on the mains so it will fit in a 350 block. These days you can find a few manufacturers offering 400 strokes with a 350 mains for less money than finding a 400 crank and turning it down.

    The 350 Small block needs to be clearanced for the stroke sometimes at the oil pan and bores, and always at the underside of the lifter valley.

    I had 383. For the money in machine work, I found a 396!

    Have fun!

    [/ QUOTE ]400's have 5.65 rods and different larger pistons.
     
  15. Beast388

    Beast388 1/2 ton status

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    [ QUOTE ]
    400's have 5.65 rods and different larger pistons.

    [/ QUOTE ]

    As Tim stated above, a 400's rods are 5.565".
     
  16. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    [ QUOTE ]
    400's have 5.65 rods and different larger pistons.

    [/ QUOTE ]

    As Tim stated above, a 400's rods are 5.565".

    [/ QUOTE ]
    Sorry, 5.565 rods, excuse me for backing up Tim's info. /forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rolleyes.gif
     
  17. SUBFAN

    SUBFAN 1/2 ton status

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    Converting to splayed caps is expensive. The caps alone run about $350, then you have to fit them to the block, have the holes drilled and tapped, align bore the mains, and buy a new set of main cap bolts (or studs)....

    For that much security, might as well look into a Bow Tie, WP, or Dart block - and they are proud of those /forums/images/graemlins/eek.gif
     
  18. Z3PR

    Z3PR Banned

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    A two bolt with splayed caps is aslong as you're talking about the aftermarket splayed caps that converts a 2 bolt mains block into a 4 bolt mains block. [​IMG]
     
  19. Longhorn4x4

    Longhorn4x4 Registered Member

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    [ QUOTE ]
    I was chatting with my brother the other day and he was talking about engines. We started to debate which was stonger setup, a four bolt main block or a two bolt with splayed caps. I said the two bolt with the splayed cab was stronger than the four bolt. I was wondering who was right? /forums/images/graemlins/confused.gif

    Also, a 383 stoker is a 350 with a 400 crank and rods that has had some machining done correct?

    Odd question, what is magnaflux checking and how does it work? Is it worth the 100 buck a part to have them check?

    [/ QUOTE ]

    All else being equal (it never really is), a two bolt main block CONVERTED to four bolt mains with splayed outer bolts will be stronger.

    The most common 383 is a 350 block with a 400 crank. It is possible to do it the other way, using a 350 crank and a 400 block. The first is more popular in trucks, the other is often seen in cars.

    Magnaflux inspection is a worthwhile investment on cranks, rods, and heads. Blocks on the other hand should be sonic checked for thickness. However, as cheap as you can buy aftermarket cranks, rods and heads, buy the aftermarket stuff and have new parts, rather than paying for used parts, inspection, and rebuilding.
     
  20. thefarside

    thefarside 1/2 ton status

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