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Discussion in 'The Garage' started by Chris_T, Mar 25, 2002.

  1. Chris_T

    Chris_T 1/2 ton status

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    It's time to do some work on my '72 and I'm looking for some advice/opinions before I move to Missouri.

    It's a 72 K5, 350/700R4 w/ AA tailshaft/NP205, Dana 44/12 bolt with 3.73's, 6" lift, 35" BFG MTs. I'll be swapping in 4.56s for sure before I leave. I want/need new exhaust. I was thinking of going to a single 3" pipe to replace the dual 2 1/4" system I have now, but I keep driving by a local shop advertising 4" systems for light trucks. If my math is right, a single 3" system has a cross-sectional area of 7.065 in sq., dual 2 1/2's have 9.8125 in sq. and a single 4" has 12.56 square inches. Too big? I'd rather buy a single muffler rather than two, so I'm still leaning towards the 3" system. Just curious if anyone has tried anything larger? My 350 is mildly built, Edlebrock performer and a Q-jet, and I don't usually turn a lot of rpms. Advice?

    I've currently got the stock ram-horn manifolds. Has anyone gained anything by swapping to the corvette ram horn manifolds? Yes, I've thought about headers, but then any crossover pipe is going behind the T-case, and I'm thinking of saving some space back there (where the second muffler would go) for a (future) air tank.

    Second of all, will I have any legal issues by modifying the exhaust system in any of the above methods moving to MO? I've been told about the bumper height restrictions, what about the drivetrain? Quite obviously the tranny has been replaced, the engine was originally a 307, it's now a 350 from an '84, points ignition changed to a Crane Cams optical trigger system .. do I need the original packaging or any other sort of documentation for any of the mods for the out of state inspection? (please say no) Anything else I need to think about with regards to bringing my truck from Alberta to MO?

    Finally, before I drive 1800 miles or so, I'm thinking of replacing the seats. Chev or Dodge buckets withthe integrated seatbelt are still out of my price range. Any suggestions on a comfy aftermarket replacement that won't break the wallet? Even better, any Canadian distributors? With the current exchange rate I'd really rather not order anything from the states until my paycheque is in US dollars.

    Thanks in advance,

    Chris
     
  2. Little Giant

    Little Giant Registered Member

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    <blockquote><font class="small">In reply to:</font><hr>

    If my math is right, a single 3" system has a cross-sectional area of 7.065 in sq., dual 2 1/2's have 9.8125 in sq. and a single 4" has 12.56 square inches. Too big? I'd rather buy a single muffler rather than two, so I'm still leaning towards the 3" system. Just curious if anyone has tried anything larger? My 350 is mildly built, Edlebrock performer and a Q-jet, and I don't usually turn a lot of rpms. Advice?

    <hr></blockquote>

    Your math is right, but from what I have heard a low rpm torqueing motor does not need large exhaust. Yes, the cross sectional area of the 4" is much larger. But the surface area of the exhaust pipe is also is larger, which means the exhaust gasses will cool quicker. Cooler gasses will have more resistance flowing down the exhaust pipe. So, it is possible to go 'too big' and actually hurt performance. I've heard if doing dual exhaust, 2-2.25" is just about optimal, anything larger hurts more than helps. Though I have to admit have I cannot reference any numbers that supports this argument one way or the other, just something I have read.

    <blockquote><font class="small">In reply to:</font><hr>

    Second of all, will I have any legal issues by modifying the exhaust system in any of the above methods moving to MO?

    <hr></blockquote>

    I don't know much about Missouri emmisions programs, though I can say it depends on where you will be living. "If the vehicle is registered to operate in St. Louis City, St. Louis County, St. Charles County, Franklin County, or Jefferson County, the vehicle is subject to an emissions inspection." Took me about 2 minutes to find that...check out <a target="_blank" href=http://www.dor.state.mo.us/mvdl/>http://www.dor.state.mo.us/mvdl/</a> You should be able to find out more information there. I would say the biggest concern would be on what they consider a legal engine swap.

    Sorry, I don't have any input on your other questions.
     
  3. wayne

    wayne 3/4 ton status

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    I would say go with the 3" exhaust. You can go with headers and have a y pipe made up to go in front of the t case and shortie headers would work a little easier. As far as emmissions I doubt with a 72 you will have to worry about them to much. About the only cheap replacement seats are fiberglass buckets but they probably won't be comfortable for an 1800 mile trip. You can look around in junkyards for some out of a newer car or truck and you might have to fab up some mounts.
     
  4. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Whereabouts in Missouri are you moving to?

    My wife has grandparents in Moberly, which is north of Columbia.
     
  5. Chris_T

    Chris_T 1/2 ton status

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    Moving to Columbia, have a post-doctoral research position starting there in early July.
     
  6. Chris_T

    Chris_T 1/2 ton status

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    Anyone else with thoughts?
     
  7. LKJR

    LKJR 1/2 ton status

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    Wes!!!
    Who are your wife's grandparents..I was born in Columbia and lived in huntsville for awhile and my grandparents lived in huntsville forever. Man it's a small world
    My grandparents were Mary and Clifford Key lived off of BB you may ask if they knew them.
     

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