Which Slant 6 to build?

Slant 6 Engines

  1. smitty040

    smitty040 Well-Known Member

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    I have a 1967 Dart GT. When I purchased the guy gave me 2 extra motors as it was his last A body. One is a 1981 Slant 6 out of a Dodge truck, cant confirm the block casting as it is laying on that particular side. What appears to be a 1968-1970 Slant 6 (2806830-6) with 5 freeze plugs. A 1966-1967? (2463430-25) Slant 6 with 3 freeze plugs that is currently in the car. If I were to focus on one of the motors to do a complete rebuild and do minor HP upgrades (cam, super 6, HEI) which would be best?
     
  2. whitepunkonnitro

    whitepunkonnitro FABO Gold Member FABO Gold Member

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    Go with the later engine. It's got a cast crank that is 20 pounds lighter than the early one. Just as strong.
     
  3. 2 Darts

    2 Darts A-body Addicted

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    Actually the cast crank was introduced in the middle of MY76 in the cars. Due to less inertia, it would be preferred on all but the most heavily modified engines. I'd go with the 81 primarily because the head already has hardened valve seats.
     
  4. smitty040

    smitty040 Well-Known Member

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    Is there a way to confirm cast crank? I do have easy access to that as the oil pan is off. The guy gave me a car oil pan to go with it. Cherry picker and engine stand are on my wish list. I too was thinking to build the 81 due to hardened seats and hydrolic lifters. Just wanted to see if there was anything that would stand out as an issue or benefit of going with a late model motor.
     
  5. BWA

    BWA Well-Known Member

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    81 would also have the better head, with Peanut plugs, no leaky plug tubes and seals to mess with.

    :burnout:
     
  6. Brandon Weaver

    Brandon Weaver Well-Known Member

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    68-71 head would be my choice. Hydraulic lifters sound great, but then it don't take well to more compression. The most popular way you get more compression with these engines is to mill a certain amount off the head and/or block, typically ~.100, but measurements need to be taken. Taking that much of tends the wreck lifter preload, requiring new custom made pushrods. Mechanical rockers have adjustable lash that can take the .100 cut.

    Also, it seems like the consensus over at .org is hardened valve seats were a solution to a problem that may or may not have existed in the 70's but isn't much of a problem now. In other words, you can go without them and not have a lick of problems.

    Just something to think about!
     
  7. Darter6

    Darter6 Well-Known Member

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    The crank pilot hole changed in 1968. The 67 and older has a small pilot and requires a flexplate and converter to match. 68 up have the more common larger pilot. I ran into this when I went to buy a performance 904 torque converter and was using a 67 engine and a 71 transmission.
     
  8. memike

    memike Super Moderator Staff Member FABO Gold Member

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    The first and biggest reason why I pulled my 170/6 out of my 66 Valiant, it was a great engine and I needed to get rid of the standard :pale: small pilot hole :banghead:
     
  9. smitty040

    smitty040 Well-Known Member

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    Lucky for me the 68 motor did come with a transmission attached. Claimed it ran when he pulled it out but he didn't remember the car or why it was pulled. Looks like it's best to create a Frankenstein set up if I'm tearing everything down for a complete rebuild?
     
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