Stock 383 2 bbl idle sound.

Engine, Transmission & Driveline

  1. 67 ragtop

    67 ragtop New Member

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    Quick question, Does the stock 270 Hp 383 in 1967 have a slight lope to it. I did notice in the service manual that it looks like it has about a 214 intake and 224 exhaust at .050 lift. That is if I did my math correctly. Anyway I just got this car running decent and the idle surprised me.
     
  2. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    In the C body world.... (I stress that since similar threads/topics beat this to death by adding B/E cars to the mix)
    The 2bbl 383,4bbl 383HP and 350HP 440 used the same cam.
    Also 67 was last year for closed combustion chamber heads (depending on build date 516 or 915 heads,both small valved .)
    So,yeah it will have a nice idle.
    Chrysler engineers were known to spec cams with short duration with some decent lift.
    BTW,are you running points? Pertronix? or electronic ignition?? what is the timing set at and what RPM?
    Cheers
     
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  3. 67 ragtop

    67 ragtop New Member

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    I am still running points, however I am going Pertronix as soon as I get new tires and exhaust paid for. I am running timing at 12 degrees btdc @ 600 RPM. dwell is at 28 degrees.
    I am trying to decide between the Pertronix II or III. I like Multi-spark discharge but am not sure if it will help this one out. It did wonders for my FE but that was with a 292H cam. On that I run a Mallory Unilite and Holley Annihilator ignition that they don't make anymore. My brother and I are arguing about whether or not to put a 4 bbl on it as this is going to be just a nice cruiser.
     
  4. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Keep it simple do the Pertronix I or II. use a hotter coil like a Accell Super Stock or MSD Blaster 3 that mounts in factory loaction. Heck paint them black and nobody would notice,LOL!
    Timing is good. Better than stock,IMHO and where most older engines like to run on today's gas.
    What is your full mechnical timing and at what RPM does it come in?
    Big blocks like about 34 to 36 degrees around 3000 RPM
    You can run more gap in the plugs with the hotter ignition. Factory is .35 so open them .37 or .38.
    As you may already know,use a good qualiy set of wires,Taylor or Neihoff.
     
  5. HWYCRZR

    HWYCRZR Senior Member FCBO Gold Member

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    My 383 2bbl runs very smooth at idle with the stock cam. No loping. If I am a little rich it a little too far advanced I may get a little mis. The tach maybe varies 5-10 rpm. Probably depends on the fidelity of the tach. If your mechanical timing starts advancing close to your idle speed you could hear more variations.
     
  6. CBODY67

    CBODY67 Senior Member

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    Lope???? From a mild cam??
    Chrysler never did put .050" duration specs on their OEM cams, but MP's Larry Sheppard and the Race Manual state that their .050" duration is more like 80% of the advertised duration. The .050" Duration specs came about in the later 1970s, as a means of comparing aftermarket cams for their true duration rather than advertised. Although there IS a SAE-Specified method to measure camshaft duration, intake and exhaust, which relates to the initial lift from the cam's base circle and any "ramps" that might be in the lobe's profile.

    When I put the old Mopar Perf electronic ignition kit on my '67 Newport 4bbl, I used a MSD 5C box on it. The old, basic street multi-spark box. Made no real difference in anything, just that I know it's there. With NGK V-Power plugs (pre-Iridium time frame).

    I put 906s on in order to drop compression ratio a bit, but still some trace clatter at WOT with factory timing and 92 pump octane fuel. With a '72 Imperial y-pipe back 2.5" "sewer pipe" single exhaust system (when I could still get the pieces from Walker Exhaust).

    The idle should be smooth in gear, brake on, with the a/c running full blast at "hot base idle", as it was meant to be. No exhaust rumble as similar Oldsmobiles tended to have. But not a wimpy sound, either.

    With the ignition points, the dwell might be toward the small side of the spec, but the main thing is to set the points and THEN the initial timing. As the dwell changes, so does the base timing. With a distributor with some wear on the distributor lobes, getting within the specs is good, though.

    Enjoy!
    CBODY67
     
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  7. CBODY67

    CBODY67 Senior Member

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    In looking at .050" duration specs, you also have to consider the size of the motor into that equation, too. A small cam in a big motor will run nice and smooth at a 600rpm idle. The same duration cam in a small motor will, in comparison, be much more radical, as a result. Plus valve sizes and how well the "head ports work".

    You can compensate for poor port flow with more cam, to a point that the idle gets too rough. You can increase port flow with the same cam and get more power across the board, until port velocities get too lazy at low rpm (for good throttle response). A balancing act of massive proportions and orientations. Of course, axle ratio is a player in this deal, too!

    CBODY67
     
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  8. 67 ragtop

    67 ragtop New Member

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    I used the 80% of advertised duration. Thanks for letting me know that Chrysler used .006. every company used different points back in the day. That is also why I said did the math right figuring out duration from the manual. trying to get the LSA etc. So basically a wild assed guess. I am trying to figure out how to post a video.
     
    Last edited: Feb 17, 2020
  9. Gerald Morris

    Gerald Morris Well-Known Member

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    After installing a WELL rebuilt sock Stromberg WWC on Mathilda this week, I've returned timing to 12.5 BTDC and am getting about 18.5 inches vacuum at 500 rpm curb idle. I run NOS points, condenser, rotor and cap too when I can get them for good prices. That old motor now is purring and running more efficiently than it has for some decades, if I read the history of it right from sundry parts replaced over the past 4 years. Changing the timing set this past Christmas helped smooth out some stutter too.

    Not too surprisingly, pre-ignition chatter has gone and it might be running slightly cooler too.

    The stock 1966 setup for a 383 2 barrel with a 2.76 rear end and 516 heads works very nicely! I'll be taking gas mileage data for the next couple weeks. I note that by running Chevron 91 octane city mileage jumped to 12.5 mpg. With Shell, I got 11. GOOD gasoline makes a substantial difference.

    All of which is to re-iterate, Willy Wirtman remains one of the most under-praised V-8 wizards to have drawn breath! I have come to truly RESPECT his engineering, and am very happy to stick close to it.