Vintage race engine (273 vs. Slant 6)

Mopar Racers Forum

  1. Pan Am Valiant

    Pan Am Valiant New Member

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    I'm planing on doing some vintage racing with my 65 Valiant.
    The classes are limited to engines and speed parts from the era so I'm trying to decide between a 273 or a Slant 6.

    Below are the allowed modifications.
    I'd like to hear your suggestions.


    6 Cylinder

    Allowed modifications:
    Those ones considered as from the “period” (if there exists proof or evidence) and approved by
    scrutineering.
    To improve the ignition system.
    The use of alternators instead of generators.
    The uses of tube exhaust headers.

    8 Cylinder

    Allowed modifications:
    Those ones considered as from the “period” (if there exists proof or evidence) and approved by
    scrutineering, in all V8 engines powered vehicles which original weight is below 3,200 lb. (1,452
    Kg.).
    The maximum intake permitted will be one carburettor with 2 barrel of 500 cfm each.
    A maximum overbore of 0.040” (over original displacement of the model available in 1965).
    To improve the ignition system.
    The use of alternators instead of generators.
    The use of modern tires of maximum (no lower number) aspect ratio 55, 60, 65 or 70 (only if they
    are fitted in the original wheel diameter and 6 inches width maximum wheels).
    The uses of tube exhaust headers.
     
  2. bamacuda

    bamacuda Well-Known Member

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    sounds like fun!
     
  3. robert 68 cuda

    robert 68 cuda Well-Known Member

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    if i were you 273 all the way just find you self a 273 power pack engin there small littel revers solid lift cam you can get a lot out of the littel bugger hope you have fun
     
  4. RAPIDTRANSIT

    RAPIDTRANSIT Active Member

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    273 with a edelbrock LD4B, Call Jim at Racer Brown for a small solid, Dougs headers.
    Road Race??
     
  5. RustyRatRod

    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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    It surely seems that the slant 6 is allowed fewwer mods than the V8. I wonder why? Seems like that would be the other way around.
     
  6. Oldschoolcuda

    Oldschoolcuda Early-A Body Nerd FABO Gold Member

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    Welcome to this fine site. Read a recent article( forget what mag.) about a valiant wagon with 273 running in vintage drag class. Rules look similar with stipulation of 2bbl only. Scarey thing is this little screamer was running in high 12's/low 13's.

    Oldschoolcuda
     
  7. MoparJoe20

    MoparJoe20 Well-Known Member

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    If you're competing against other V8 cars of the era I would build the /6, if it's a HP/LB class I would build a hot 273, I would hate to spend the $ on a 273 if you have to run against a 327 chevy II or a 289 falcon.
     
  8. Pan Am Valiant

    Pan Am Valiant New Member

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    Thank for the input. When I posted, I cut out a lot of the extra rules as I'm just trying to choose between the two engines. Classes are based off # of cylinders. Cars up to 1965.

    I looked up the LD4B and I see that its a 4BBL . As the rules state 2BBL for V8, I don't think that'll work.
    I have found a source for the 4BBL pistons for the 273, so that would raise compression to 10:1.

    As for /6, Offy makes a 2x1 BBL and a 4BBL manifold. I doubt I would ever find a Hyperpak and I doubt I would want to pay the price if I did.

    Rapid Transit, yes I want run the Carrera Panamericana. For those who are unfamiliar, it starts at the bottom of Mexico and ends in Neuvo Laredo. It mostly runs through the mountains of Mexico and cars rarely exceed 85mph.
    So, some fuel efficiency and torque could help.
     
  9. Pan Am Valiant

    Pan Am Valiant New Member

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    Oldschoolcuda- that was in an issue of Mopar Action.
     
  10. RAPIDTRANSIT

    RAPIDTRANSIT Active Member

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    Back when I worked at a dodge dealership we had a chrysler 300 come in that road race in Mexico I believe it was that series this was about 13 years ago.
    When I mentioned the LD4B I was thinking of a carb adapter. ( I run a 500cfm Holley 4412 on my oval track Mopar) plus it would help with the front weight and they were avalible early in the 60's for the 273. The chevy's and the ford's would NOT scare me, the chrysler has a better rod ratio, better heads, rocker arms ect.
    Closed chamber head with some quinch to run there junk fuel..... this sounds like fun when do we start!
     
  11. 66dartgt

    66dartgt Well-Known Member

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    If you decide to run a 273 - look into the wrist pin weights. The standard wrist pins in a 273 weigh a TON. I think they did this because the crank was designed to work with the bob weights for a 318, probably to save money in manufacturing !

    You should be able to get away with a much lower bob weighted engine if you investigate this aspect. Which would lead to a faster, perhaps higher reving, more durable assembly. There might be some problems with the crank lightening process as well. But, I'm no expert on balancing motors, just a keen observer of the parts in engines.

    For an intake - you might consider a 273 2 bbl intake - the 66 vintage and earlier types are single plane low rise pieces. On the other hand, are you restricted to using only cast iron ? Could you use a vintage 4bbl AL intake with an adapter for a 2 bbl ???

    Keep us posted on your decisions, this sounds interesting.
     
  12. dart4forte

    dart4forte FABO Gold Member FABO Gold Member

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    Paul Wong T/S 14.76 13.986 -0.774 Stock Eliminator

    He runs a early B body with a stock 273 2 barrel
     
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