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  1. #1
    Senior Member BasicQ's Avatar
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    Default Which one would be quickest et?

    Car: HQ two door, 3350 lbs with driver
    TH350 auto box
    4000rpm converter
    9” diff 3.89:1 ratio
    26” rear tire

    Three different camshafts

    What hp/torque curve would produce best et?

    The one with the most torque close to 4000rpm to get out of the hole, the one with highest peak hp or the one in between?

    1)
    [img]https://i.ibb.co/RDwXfq6/91-F0979-A-CB2-F-4976-A950-C6-C15-C483-C14.jpg[/img]

    2)
    [img]https://i.ibb.co/jLmHntX/1-D386310-89-B3-43-FB-B95-E-DCF7-B7-D3-C932.jpg[/img]

    3)
    [img]https://i.ibb.co/1m1g5Mg/38-CFF65-B-D558-4-F14-9-C19-6672-F44-C178-E.jpg[/img]
    Last edited by BasicQ; 10-05-2021 at 07:12 PM.

  2. #2
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    None of them, converter is way too low and probably the wrong diameter as well.
    They will all be turds.

    The last one would be the better of a bad bunch.

  3. #3
    Senior Member BasicQ's Avatar
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    Default Which one would be quickest et?

    Quote Originally Posted by HQ 368 View Post
    None of them, converter is way too low and probably the wrong diameter as well.
    They will all be turds.

    The last one would be the better of a bad bunch.
    What converter would you recommend?

    Last curve is what I have now (although only simulation) the other two are camshaft changes to fit within the very restricted .112” max lift @tdc heads I have. Autoflite recommended and built converter 18 months ago.


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    Last edited by BasicQ; 10-05-2021 at 10:18 PM.

  4. #4
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    Nothing Under 5K.
    For an E.T. closer to 5500 rpm, start there and track data will help zero in on where it needs to be.
    Torque isn't really falling off until after 5500.

    The converter you have is better suited to something with a smaller cam or a burnout car.

    Would be ok if you were going to hit it with some spray.

  5. #5
    Senior Member BasicQ's Avatar
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    Hmmm.....spray

    The cam for the last chart which I have now is: int 244 @.050” exh 252 @.050”. LSA 110 on 106 cl. Static comp 11.4:1.

    When rocker geometry is sorted the Trickflow twisted wedge (sbc) biggest flaw is intake piston to valve clearance. Have to find lobes and juggle intake cL that keep lift at tdc below .112”. The first two charts are potential cam changes for what I consider a last effort to get all I can out of these heads before moving on to a head without such restrictions. They flow ok with 271cfm @0.500” 28” intake.

    Street/strip car so everything is a compromise. I know et will be better with different diff gears but not the best for street driving.


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  6. #6
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by HQ 368 View Post
    Nothing Under 5K.
    For an E.T. closer to 5500 rpm, start there and track data will help zero in on where it needs to be.
    Torque isn't really falling off until after 5500.

    The converter you have is better suited to something with a smaller cam or a burnout car.

    Would be ok if you were going to hit it with some spray.
    What are the indicators of selecting 5000+rpm converter?

    Is it the torque peak at 4500?

    The other two Cams were:
    Int 250* @.050” exh 258* @.050” lift int .573” exh .592” lobe sep 106* int lobe cL 106*

    Int 254* @.050” exh 262* @.050” lift int .582” exh .602” lobe sep 110* int cL 108*

    Would you have another suggestion?

    I understand this is only simulation software but short of pulling the engine and dynoing it’s the only way to get an estimate of hp/tq curves and compare changes.


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    Lots of indicators, cam, comp, engine size, weight, useage, experience and too many others to list.

    Basically anyone running a small block with a cam in that range is automatically going to need a converter in that range if your looking to put it down a strip and get the performance out of it that it's capable of.
    Generally above peak torque for N/A.

  8. #8
    Senior Member BasicQ's Avatar
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    Default Which one would be quickest et?

    Quote Originally Posted by HQ 368 View Post
    Lots of indicators, cam, comp, engine size, weight, useage, experience and too many others to list.

    Basically anyone running a small block with a cam in that range is automatically going to need a converter in that range if your looking to put it down a strip and get the performance out of it that it's capable of.
    Generally above peak torque for N/A.
    I was curious what in those charts told you a 5k plus, but your second paragraph in the above quote pretty much covers it.

    Never ran a converter of that size on the street. With a well made converter of that size is there any downside in a street driven car ie going on cruises etc?


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    You can dumb it down to small cubes, peak torque etc. Its more complex than that, easy to get into a ball park but to dial it in comes down to the finer details and data.
    I don't find cars with 5K+ converters have too many negatives, the right converter makes the combo at the end of the day.

    There are guys on this forum running 6k+ converters and cruising, probably more street racing than cruising but cruising none the less.
    Some are deep into the 9's and others not on this forum are into the 8's in street trim.
    When a particular car comes back from chassis shop in Sydney it'll run 7's once sorted.

  10. #10
    Do you ever leave? EH179's Avatar
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    5k TCS converter here, regularly street driven. Keep the fluid cool and all sweet for over 6 years now.

  11. #11
    Senior Member BasicQ's Avatar
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    So it seems the best thing I could do to get more out of these heads is up the converter?

    I am becoming more curious why the guys at Autoflite would recommend and build me a 9-1/2” 4000rpm eliminator converter. Would it be because I ticked the ‘street/strip’ box?


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  12. #12
    Do you ever leave? EH179's Avatar
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    You could leave the engine and diff gears as is, and improve the 60', therefore ET, with just a converter change.

    Autoflite? never heard of them!

  13. #13
    Senior Member BasicQ's Avatar
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    Default Which one would be quickest et?

    Quote Originally Posted by EH179 View Post
    You could leave the engine and diff gears as is, and improve the 60', therefore ET, with just a converter change.

    Autoflite? never heard of them!
    Better known as Dominator Converters.

    https://www.dominatorconverter.com.au/

    60’ at Calder was 1.73. Improvements to be had there but that was with the old converter that was around 3-3.5k rpm. Other improvements have been made since then too.

    What do you think is a good achievable 60’ for my combo, high 1.6’s


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    Last edited by BasicQ; 12-05-2021 at 09:15 PM.

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    A 245 mm body converter is a readily available core with plenty of available parts. There are good margins to be made on that type of converter

    8" on the other hand is virtually impossible to find cores, you have to buy everything brand new and they get expensive.

    You should have enough power there to get into the 1.5's but that might take a bit of work or it might come easily. At the least 1.6's, stage nice and shallow and you will get the best 60"

    Converter makes or breaks the car, sometimes both.....

  15. #15
    Senior Member BasicQ's Avatar
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    Default Which one would be quickest et?

    So with the converter I have is there any point in changing the cam I have? I won’t be changing this converter until another engine build is done to avoid yet another converter swap or the build being tied to an existing converter.

    On the shelf I have a COME HVS-252:
    Int @.050 252* adv 289* lift .570”
    Exh @.050 259* adv 296* lift .587”
    LCA 108* ICL 106*

    This will cost me nothing more than a set of lifters and gaskets.

    Would it be worth it or would I be wasting my time doing that change while still having the 4K converter?


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