6.0 LS carb tuning

Discussion in 'High Performance Modifications' started by jeff swisher, Feb 26, 2020.

  1. jeff swisher

    jeff swisher Veteran Member

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    I am going to see where his power from the unit is coming from.
    he may have hooked it to the HEI positive Battery wire.
    I heard that does not work all the time you need to use a relay and feed it with battery positive not power from ignition switch.

    Odd thing is it did it all of the sudden. He did mention that he had revved it to 7200 rpm and thought that may have messed something up. But many days after that is when it started.
    No bent pushrods and no ticking and cranking pressures are the same as when he first put it together.
    So no bent valves etc.
     
  2. jeff swisher

    jeff swisher Veteran Member

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    Buddy put his 800 edelbrock back on with the jetting it had before all this started and went for a drive.
    It acted the same way Popping etc.
    He switched the MSD tune to Truck and it did the same and then to LS1 and then to custom 4. they all did the same but the truck felt down on power at 1/2 throttle.
    He switched it back to "custom 4" and it acted perfect.
    Got all his power back and No popping revved it to 7000 rpm no issues.

    Odd that it cleared up.
    He said he got on it 3 times first and second to 7000 rpm no issues.
    If he has issues again I will inform you all.

    He does have a relay set up for powering the MSD box.

    Answer me this.
    He has never had a laptop or anything hooked to this MSD LS box and it is new.
    So Custom 4 must have a baseline tune in it.
     
  3. junkyardZ28find

    junkyardZ28find Veteran Member

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    I think the LS cam profiles might not lend well to a carb setup. What mods were done to that 4779 that didn’t seem to work out very good? Being a Holley guy myself I can’t imagine ANY world where I would prefer any Eddy carb over a well tuned Holley.
     
  4. jeff swisher

    jeff swisher Veteran Member

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    The Holley is mine and stuck on as a loaner because his Edelbrock seemed to be the issue But it is not the issue at all. We did not have jets large enough for the Edelbrock so we drilled some to try and fix the Supposed Lean popping issue.
    Did not work so my tweaked 4779 went on because I have a lot of huge jets that would determine if it was a lean pop which it was not.
    Venturies are enlarged a little and polished a bit ,boosters centered and thinned a little.
    Epoxy a plenty on the air entry. Thinned throttle shafts and small head screws in the throttle blades.
    It will move some air. Yea it is dirty but it runs excellent on all engines i have stuck it on.

    I agree most LS profiles are not designed for a carb.
    The cam profile is not an LS profile though.
    It is The old LT4 Hot cam 218-228 @ .050 with .492" lift both sides and that is with 1.5 rockers.
    GM stuck those on a 112 LSA.
    The cam shop has a master of that cam and he stuck it on the stock 6.0 cam he pulled out.

    With 1.7 rockers it is 222 [email protected] .050 and .557" lift and stuck it on a 109 LSA and closed the intake valve earlier.
    It actually has more cranking pressure than the stock LS LQ9 cam now.. He checked cranking pressure before and after.
    Picked up a bunch of bottom end and had to put a posi in it .. the thing was spinning the tires way easier than the stock LQ9 ever thought of.
    Posi helped a little but it still blows them off.
    More low end more mid and more topend..The cam works very well.
    I ported the heads on it and that probably helped a bit in the power department also.
    3" exhaust on it.
    The cam shop has ground a lot of those LS cams with that LT4 profile.

    I had it made for my gen 1 sbc roller but had him grind it 228-228 @ .050 and stuck it on a 110 LSA.
    I wanted gentle lobes..Gm usually has that in their cams.
    I could have had a Comp roller profile but I had no name link bar lifters I pulled out of a vehicle and figured 313 rate beehives and a gentle profile would get the RPM I want and still make power..It did just that I have had mine to 7200 rpm without any issues. Usually shift at 7k though

    [​IMG]
     
    Last edited: Mar 6, 2020
  5. jeff swisher

    jeff swisher Veteran Member

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    6.0 LS Zero cranking pressure cylinder #1
    Finally something to go on.
    He was so excited that it finally did sort of break something as he was about to get another MSD controller, he said MSD has no customer support for these controllers and they do not repair them. Just get a new one and start over.

    He will be pulling the head tomorrow. If it is not off already.

    More to come.
     

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