Camshaft and torque convertor

Engine, Transmission & Driveline

  1. Whiplash

    Whiplash New Member

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    I have a 1967 Chrysler Newport 4 door very cool car I have questions about what cam and convertor the car was 2 bob 383 2.76 and 25 tall tires we have Holley 4160 vaccume secondarys and eldebrock dual plane performer any suggestions would be greatly appreciated thanks
     
  2. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Need more information. Is the engine still stock except for the carb and manifold upgrade? The stock 2BBL engine had a 9.2 compression ratio and in Chryslers the 2BBL and 4BBL both used the same cam for '67. Cam was a .425(lift) intake/.437 exhaust. Some additional performance can be had by upgrading to the 440 high performance camshaft with the appropriate high performance valve springs. If you are looking for additional performance, going to 3.23 gears would be a good start. You can gain some additional performance by going to dual exhaust with the high performance manifolds. The factory stall speed on these cars was usually in the 1600-1700 rpm range. If you are going to alter the stall speed, you need to decide what type of camshaft you want and match the stall speed to the start of the peak torque range of the cam. Usually just changing convertors will not cut the mustard as they say because you need to also upgrade the valve body and governor of the transmission as part of the upgrade. This is best done as part of a transmission overhaul. If you are changing camshafts, it would also be a good time to have someone who knows the 383 well to evaluate the engine as to its condition. If you are taking about a 50 year old engine with something near 100k in total miles, you are asking to scatter the engine if you do not do the performance upgrades as part of a quality rebuild.

    A lot of this depends on what you are trying to achieve and how much you want to spend.

    Dave
     
    Last edited: Oct 2, 2019
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  3. CBODY67

    CBODY67 Senior Member

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    Chrysler was famous for building "combination engines" back then. Meaning that everything was designed to work together for BEST results. What that means in that you'll can upgrade the cyl heads to the 1.74" exhaust valves with appropriate stiffness valve springs. Which will put you with a '68-spec set-up (one reason the post '66 383 2bbls were rated at 290 horsepower from the earlier 270 horsepower (using the 256/260 cam rather than the 252/252 of prior times), plus the larger exhaust valves.

    A cam with something like the '67 440/375 cam would help, too, teamed with the '68 Road Runner 383 spec torque converter AND related hi-upshift governor for the trans. Plus a good dual exhaust system to complete the replicated "combination" of the '68 Road Runner 383 specs.

    I suspect the cyl heads' valve guides will need some attention as a part of the possibly needed valve job. So, with them off, you can physically "cc" the chambers to determine the true compression ratio of the particular motor (which could be a bit less than what the Chrysler rating might be). But they'll probably need to be "surfaced", best done with a mill rather than a "rotating rock" surfacer. The formula to figure that is in many places.

    In our Mopar Club, we had a bunch of guys with factory OEM spec cars. When tuned and driven correctly, even with the OEM HP exhaust manifolds, they were extremely hard to beat at the drag strip! One tried to go with "more cam" and the car went slower ET wise, but was faster through the traps. On street tires. So he went back to "stock" HP cam, where he was to start with. A more consistent "pull" rather than "top end rush" which didn't make up for what was lost on the bottom end of things.

    Lunati has some "modern version OEM HP cams" which look pretty nice. BUT in a heavier car, with reasonably stock gearing, looking for more torque is better than chasing 6000rpm horsepower, by observation. Which gets to the orientation of "a torque motor that will make power at 5000rpm".

    Enjoy!
    CBODY67
     
  4. stubs300

    stubs300 Senior Member

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    Some grammar & punctuation would be nice!
     
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  5. Whiplash

    Whiplash New Member

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    Thanks y'all
     
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  6. 67Monaco

    67Monaco Old Man with a Hat

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    Stick with the stock cam and converter unless you plan on changing rear gears. You're kind of short with the 25" tire. I would think stock would have been about 27" or so. With that you're gaining off the line or off of a stop, but you're losing in top end speed. I think the 25" tire with the 2.76's puts your effective gear at 3.21 or so.

    Also until you do top end work to increase spring pressure and valve travel you're going to be limited on cam to a fairly low lift. You'ere going to top out at about .510". Or at least that been the generally accepted max lift range on factory springs and valve guides.
     
  7. bajajoaquin

    bajajoaquin Senior Member

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    Seriously?