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455 Pontiac from a 400 Pontiac block?

Discussion in 'Other Rides' started by Blaze, Apr 9, 2001.

  1. Blaze

    Blaze 1/2 ton status

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    I was scanning through some Trans Am forums and came across a post where a guy was talking about building a 455 clone with a 400 block and a 455 crank and pistons. Or maybe it was just a crank and connecting rods, can't really remember. Anyway, is this possible? I can pick up a decent 400 at the junkyard for $200 that needs a serious rebuild. Would I be able to use a 455 crank in the 400 block and the 400 crank in my 350 block? I know Pontiac parts interchange, but this seems a little extreme to me. Anybody know anything? Steve Chin?

    [​IMG]<A target="_blank" HREF=http://www4.ncsu.edu/~brschoch>http://www4.ncsu.edu/~brschoch</A>
     
  2. DMK

    DMK 1/2 ton status

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    A 455 block is easier to find than the 400. The 455 was also used in full size cars. 400's were used in performance cars. So there are more 455's around. Doubt you could find a crank without buying a block. Pretty sure cranks won't interchange.
     
  3. Blaze

    Blaze 1/2 ton status

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    Actually a 400 is easier to find than a 455 because they used them in the Trans Ams so much. There are at least 4 400s in my local junkyard and no 455s. I can easily get the 400 block and possibly get the 455 crank.

    [​IMG]<A target="_blank" HREF=http://www4.ncsu.edu/~brschoch>http://www4.ncsu.edu/~brschoch</A>
     
  4. Steve_Chin

    Steve_Chin 1/2 ton status

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    Boy, have I answered this question a good number of times. There are two ways to accomplish this. Note that the 400 is a small journal Pontiac engine and the 421/428/455 are large journal Pontiacs (3.0" main journal vs. 3.25" main journal). The thrust bearing saddle is wider on the 3.25" main engines as well. In order to put a 455 crank in a 400 block, the thrust surfaces must be welded up (a VERY specialized procedure, because nodular iron is tricky to weld) and then the main journals turned down and the thrust surfaces trued up. This is very expensive (don't believe that freak in Southern California who claims that you don't need to weld them up!).

    The other route is entirely new as of the last 8 months or so. Jim Butler Performance has had Eagle cast up some special crankshafts with the 3" main journals and a 4.21" stroke (and also 4.25" stroke versions, which require special pistons and BBC type rods).

    FWIW, the 455 blocks are VERY hard to find. Keep in mind that for most of the models in which it was offered, it was the TOP option (except in 1970 in the GTO, where the LS-1 Ram Air IV 400 was the top option). I keep looking for spares and only have a couple of blocks and cranks in hand. Cranks are as rare as blocks, so I think it's sheer folly to cut up a crank to fit a small journal block. There is also no advantage to putting a 400 crank in a 354 block. They are dimensionally the same. The 354 crank may have just a slightly lower amount of mass in the counterweights because the pistons are smaller, but that is all of the difference in the 354 crank vs. the 400 crank.
     
  5. Blaze

    Blaze 1/2 ton status

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    Thanks Steve! That answers my question! BTW, I thought a Pontiac 350 was actually a 352.3, not a 354. I've got a Car Craft at home that says it is a 352.3, but I've heard 354 used a lot. I just got an awesome deal on a 455 Olds and 400 tranny. My friend has one that he pulled out of a car that his neighbor gave him. He sold it to me for $150. It runs and everything! It runs, but it needs the carb rebuilt(4bbl Carter) and a tune up. I think I'm going to clean it up and sell it and buy a Pontiac 455 if I can find one.

    [​IMG]<A target="_blank" HREF=http://www4.ncsu.edu/~brschoch>http://www4.ncsu.edu/~brschoch</A>
     
  6. Steve_Chin

    Steve_Chin 1/2 ton status

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    Correction on the stuff available from Butler: He has the long stroke crank available for the 3" journal block, but not the 4.21" stroke crank. My mistake.

    Hmmm... Interesting on the PMD 350. all of the Pontiac guys I know refer to it as a 354. I'll have to dig up my specifications on the engine and figure it out for myself (even though I don't have a lot of interest in this displacement).
     

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