383 stroker timing/performance and temperature

Discussion in 'Troubleshooting & Diagnosis' started by erhan ergin, Apr 25, 2020.

  1. dave@ztech

    [email protected] Veteran Member Lifetime Gold Member

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    Ignore my other post, the NS at the end of the model number is supposed to mean no sensor , and it looks like on Summit it doesn't include the sensor so 131.00 is not a better deal, IF the Amazon one does COME with the sensor, then it is a better deal, sorry of the confusion , HAA HA
    https://www.summitracing.com/parts/avm-30-4110ns/questionsanswers#qa-display-detail




     
  2. dave@ztech

    [email protected] Veteran Member Lifetime Gold Member

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  3. erhan ergin

    erhan ergin Veteran Member

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    Yeah I was going to say $131 is a great deal but then I saw NS as well :)
    The one you posted from amazon is even cheaper, thanks.
     
  4. dave@ztech

    [email protected] Veteran Member Lifetime Gold Member

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    Yes these guys are sneaky , have to check the item number careful , or they will screw you, good luck , I hope it help dial in your engine.
     
  5. erhan ergin

    erhan ergin Veteran Member

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    I got the AFR gauge and it does give pretty good info on what is going on at different scenarios. I did some reading and it appears I should shoot for following ratios:

    idle 13.5 to 15
    cruise 14.7 15.5
    WOT 11.5 13.3

    I am a bit off (running rich in most daily driving scenarios).
    - I am at 12.5 at idle.
    - When I am coasting say at 1500-2k rpm it goes to 11 range,
    - part throttle it jumps to 14-15 range (this is for instance when I slow down to make a turn and then give it part throttle to speed up) ,
    - WOT It jumps over 15.5 but comes back down to 13 range quickly.
    I can adjust idle and bring it up to 13.5 using air fuel mixture screws but I am still seeing low coast ratios. At 1500-2000 rpm going 30-40 mph with no or little throttle are the main jets helping or is it all idle circuit?
    Based on the part or no throttle low ratio I think my main jets are too big? Do you agree?
    Could there be some adjustment needed for the air bleed screws to remedy the part throttle/cruize richness?

    Thanks

    Erhan
     
  6. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    It is possible that at WOT the initial 15 might be from the accelerator pump, and can be adjusted. Not certain if that is right when you stab the throttle or not.

    If you are at 13 at WOT, the main jets are fine, unless you are shooting for 12.5, then make them a bit larger. I wouldn't judge the mains by part throttle.

    Idle is a bit rich, and should be adjusted.

    Coasting may need some perspective. If you are at say 4000rpm, and let off the throttle and coasting, it will give you a different reading then if you were on the throttle getting there, or maintaining it at 4000rpm. Throttle blades are in a different position, and the reading will be different. Only look at the gauge when you are in the throttle. Another thing...if you shift gears while coasting, you'll see the reading change as well.

    Where I live, in CT, I wouldn't dial in my carb at this time of the year. The air is a lot different than when I normally drive the the car. If this is the same with you, then you may consider just driving the car till the end of the season, and do this next year when the temps are average to when you normally do drive the car. You can get it closer now, but don't knock yourself out trying to perfect it if the weather isn't perfect.
     
  7. erhan ergin

    erhan ergin Veteran Member

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    Thanks for the suggestions, I am in Austin TX and it is still between 80-90F so still quite warm. Unfortunately either the gauge or the sensor died the second day. It reads full lean now no matter what. I checked AEM support, this seems to be a common problem. Hopefully I can get a new gauge or sensor under warranty.
    When I said coasting I mean coasting around 35-40mph typical driving in town. I have a tall stall converter so I let my foot of the gas and coast quite a bit in daily driving. The revs stay around 1.5K to 2.5K and I am thinking I should be saving some gas but it looks like this is where the mixture is quite rich. I am thinking this is also due to the idle circuit being rich but I thought maybe main jets are also working at this point.
     
  8. G72Zed

    G72Zed Veteran Member

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    A lean spike getting into WOT is also a sign of a low PV opening....sometimes the numbers on the PV don't match the actual opening and does not affect the idle as it's only on the main well.

    Generally under 2,000 rpm your on the idle/transition slots, but every carb is different, it may be teetering on the mains based on what your saying, check the boosters at that rpm.

    And the main complaint on these carbs from my customers was rich idle/transition overlap...they were not happy using all that fuel and not making any power....it's all in the combo and how the IAB/IFR and E paks work together in that particular carb.
     
  9. erhan ergin

    erhan ergin Veteran Member

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    Hi Folks, I hope you all head a good holiday season and the pandemic has not ruined your lives.
    I am back to tinkering on the 70 Camaro. Last time I worked on it, the afr guage went out after the first day of use. I got a replacement O2 sensor under warranty. It is functioning as expected now. Here are some things I learned and did recently:
    1- My idle setup was completely wrong. I had too much of the transfer slot showing so the car was running very rich.
    2- As soon as I adjusted the idle screw to square the transfer slot the car will not idle. I remember in an earlier post I mentioned the car had no problem starting and idling, but it was gutless. After adjusting the idle to where it should have been and dialing in the air fuel mixture to ~ 14 range now the car is quite responsive. But it will not idle. It takes forever to warm up and will not idle unless I dial up the idle screw where the transfer slot shows up. It gets very rich when I do this.
    3- Reading thru many threads and watching youtube videos, I drilled the throttle plates. It helped some. I can almost get it to idle at proper idle screw settings but I am still not quite there. I drilled holes at all 4 throttle plates. BTW I am using a brawler 650cfm with 68 primary and 72 secondary and a 2.5 PV. I get around 7inHg idle vacuum. I tried idle timing all the way from 18 degrees to 28 degrees.
    4- My next step is to adjust the air bleeds for idle circuit. I believe the 4 outer air bleeds (2 primary and 2 secondary at the 4 corners) are the idle air bleeds right? I took one out, it is #65. I read a few places people suggesting to increase the air bleed size to lean out the idle. I am not sure if that is the right direction to go. One more detail, I have 4 corner air/fuel mixture screws and they do impact the idle A/FR but because the idle screw is too far in I cannot lean out the idle enough. Essentially, I can get the car to idle if I make it very rich at which point it will become very sluggish, if I lean it out I cannot get it to idle.

    Sorry for the looong post, any suggestion is appreciated.
     
  10. 80sz

    80sz Veteran Member

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    Use a 6.5 power valve . Square the idle slot again. Crack the secondary screw to open them some to allow more air to motor. The holes can work in primary’s but feel that’s a hack way to do it.
     

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