4 link help

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Bjs344, Sep 9, 2018.

  1. Bjs344

    Bjs344 Member

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    Wannabe promod: roots blown BBC, pg 1.80, 4.10, 34.5, 2450 lbs wet.

    Car was untameable with a bad strut and 3 flats of negative preload. Lots of power pulled was on a 4.5x a couple times but never made it.

    Question: after adjustments I'm 53% front weight with the RR 60lbs lighter than the LR. How much power would you expect this to take (i.e. How quick to the 60')? Should I take some back off the RR when I turn it up? At what point should I think about rear steer? don't think it will take a big swing, just trying to decide how hard to go after it.
     
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  2. sammy christian

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    doesn't sound that bad if you have the strut better and the preload neutral. Just put the rear steer in a little at a time as you need to for it to go straight, depends on how stiff the car is.
    I think 53-54% is fairly typical, i'm at 53.6 (2800#) same rear difference with a fair amount of rear steer and have no problem going 1.00-.02 anytime, having trouble after that. have to learn when and how fast to put power back in.
     
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  3. rb0804

    rb0804 Member

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    I like to setup cars neutral if I can. If the car is driving hard to the left I will crank some preload into the passenger side top bar. When you do this the anti-roll should be neutral as well as the other 3 bars. Like said above the stiffness of the car has a lot to with how the car behaves. Think of it like this, when you lift at the big end or you happen to pedal it in the middle the car unloads itself and does exactly the opposite of what it does leaving. Also make sure your wishbone moves freely and isn’t bound up.
     
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  4. Bjs344

    Bjs344 Member

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    Thanks guys, great feedback. Struts are fixed and revalved. It's a diagonal link, no wishbone.

    I put 1 flat of preload in it (top right shorter) to get to the rr from 120 lbs light (neutral bar) to 60 lbs light. Was 230 lbs light when it went on the scales. Antiroll neutraled after adjustments. Im debating taking the 1 flat back out.
     
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  5. sammy christian

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    as for rear weights, I've seen people way way more experienced than me say it doesn't really matter what the scales say, you still need to make the adjustments to make it go straight.
    When the engine is running and the car leaves, there are no scales under the tires.
     
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  6. rb0804

    rb0804 Member

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    I would set it neutral. Make a pass in the right lane. If it drives left add some pre-load. If it drives left harder you went the wrong way. I’m gonna say from memory 4.50’s was about the ET that we needed some pre-load. I ran a heavy big tire car a couple of weekends ago 4.60’s with no pre-load and it was driving left, but after watching the video from the rear of the car several few times I could see that the left wheelie bar was hitting the track slightly before the right one and it would unload the left rear tire and the rear of the car would wash out to the right, pointing the front end left. We raised the wheelie bar a 1/2” and the car goes very straight now. Just take everything into account before you start “blaming” things and making changes. In the case above if preload was added it probably wouldn’t of helped.
     
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  7. Bjs344

    Bjs344 Member

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    More good advice. I was able to straighten the car out with the wheelie bars with the way the car was but it was a nightmare down track.

    I totally agree with giving it what it wants no matter what the scales say. I'm also aware how quick it can get stupid if I miss the setup.

    Something I never thought about before (b/c I've only run slow door cars and medium dragsters): if I have a bunch of power out at the hit it probably wants to be neutral but if I put it all in by the shift it probably wants rear steer. Go halfway between and aim it crooked on the line??
     
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  8. turbo69camaro

    turbo69camaro Member

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    In my opinion you dont need rear steer unless your making stupid crazy hp A hi hp car will want to go left if its hooked up hard in that case make the top pass bar LONGER for your pre load 1 flat at a time 3 to 4 flats is ok

    And all adjustments for getting l link zero ed out the first time should be with driver in car full fuel load etc with anti roll disconnected
     
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  9. rb0804

    rb0804 Member

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    I agree with what Jim’s saying completely.
     
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  10. Bjs344

    Bjs344 Member

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    4 link is now neutral with no rear steer.

    Wheelie bars are 3/8 lower on right side (was ~3/4).

    I didn't move any bars but finally measured the settings:
    Bottom bar 4.5 degrees down middle holes
    Top bar 17.5 degrees down middle hole on housing.

    That's probably not where I would have set them if starting over but I'll keep them there for tomorrow.
     
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  11. 57Chev

    57Chev Member

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    If that's 4.5 degress down to the Chassis that would be to much. If the tracks you are running on are good then it should be slightly up hill and if you are on marginal tracks try .5 down to the Chassis.
     
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