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My carb LS1 being a pita.

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    My carb LS1 being a pita.

    So I've built an LS for my HQ GTS...

    383 COME stroker kit, Vic Jr manifold with a 750 QFT on there.. i know should have stayed injected.. but I didn't.

    Using an MSD6012 ignition control box and having constant issues with start up/idling. Had it starting regularly and idling ok after lots of faffing about but then it went to shit again.

    Basically, it doesn't want to start a fair bit of the time and used to give cam and crank sensor errors.. which is common with the 6012 from what I've read. It's had multiple new sensors put in so we don't believe it's them.
    Sometimes it'll start fine no issues, othertimes it'll go bang and shoot a flame out the carb.

    As above, at 1 stage had it start regularly, idle was fantastic and AFR's were 12.5:1.. then I put the air filter back on and it went to shit.. went rich (as expected but far more than I thought it would) and turned into a dog again.. filter off and thought would be happy again.. nope now it would idle for a bit then idle would start to climb.. turn engine off and it would diesel for a little bit sometimes.

    Now before I strip it all off and throw some sort of injection on and proper ECU... is it possible that my cam shaft is causing some hiccups?

    It's a compcams big muthathumpr which is meant for a 346ci LS and not a stroker.. mate said it took him forever to dial the cam in when putting the combo together for me.. so is it possible this will further complicate things such as timing (which seems to be an issue i'm having)...

    I'm not massively skilled on working with engines and this has been my sort of learning project with help of mates who are more knowledgeable but I was chuffed that I could get it started and idling well and even reversed it out of the garage)
    Timing maps aren't wild with a 16* timing set across the board which from what i've read is decent enough (from guys on ls1tech/etc).

    So kind of stumped and don't want to have to send it to someone and spend a fortune on trouble shooting without exhausting all options I can do myself.

    #2
    If you put a timing light on it how stable is the timing? Don't use a dial-back timing light when doing this, use a conventional timing light.

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      #3
      Originally posted by elfturbomax View Post
      If you put a timing light on it how stable is the timing? Don't use a dial-back timing light when doing this, use a conventional timing light.
      Will check this thanks

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        #4
        Muthathumpr is a crap cam, I dunno why people use them. But shouldn’t be causing the issues you’re having. Sounds like you have a pretty bad vac leak? Were the heads decked? Does the manifold fit the heads properly? Did you use the thick paper felpro intake gaskets?

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          #5
          Originally posted by bpm View Post
          Muthathumpr is a crap cam, I dunno why people use them. But shouldn’t be causing the issues you’re having. Sounds like you have a pretty bad vac leak? Were the heads decked? Does the manifold fit the heads properly? Did you use the thick paper felpro intake gaskets?
          Yep to all 3 as far as I am aware,

          nabbed this pic off google.. but I am running the same standard valve covers... the pipes off the top 1 are just open with nothing going from them to anything.. would this be causing an issue?

          I bought the came ages ago because i just wanted a wanky idle. I know now can get far better cams which can provide the idle and more power so open to suggestions.

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            #6
            I have problems with mine starting but because i rarely drive it i've just accepted it until now. It's even worse after the car has gotten to temp. I have to pump the throttle multiple times on startup to pretty much flood the intake. If there isn't enough fuel it just backfires out the carb.

            I'd hook up a laptop to my 6010 and it won't even show a tach signal when cranking but then as soon as the car starts the tach would work. I'm not sure if it's just the msd or maybe the starter isn't spinning the motor fast enough. The coils still fire so it must be getting a crank signal.

            I bought a daytona smart spark and the adapter harness to use the msd wiring last month. I haven't installed it yet but i'll let you know how i go when i do in the next few weeks. Depends if you get fed up and just go efi before i report back to see if it fixes my issues.

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              #7
              Those barbs on the covers will just let the crankcase vent to atmosphere. It won't cause any problems apart from smelling and letting dirt possibly get into the engine.

              Comment


                #8
                Originally posted by Alexg View Post
                I have problems with mine starting but because i rarely drive it i've just accepted it until now. It's even worse after the car has gotten to temp. I have to pump the throttle multiple times on startup to pretty much flood the intake. If there isn't enough fuel it just backfires out the carb.

                I'd hook up a laptop to my 6010 and it won't even show a tach signal when cranking but then as soon as the car starts the tach would work. I'm not sure if it's just the msd or maybe the starter isn't spinning the motor fast enough. The coils still fire so it must be getting a crank signal.

                I bought a daytona smart spark and the adapter harness to use the msd wiring last month. I haven't installed it yet but i'll let you know how i go when i do in the next few weeks. Depends if you get fed up and just go efi before i report back to see if it fixes my issues.
                I had a 6010 and ditched it for the 6012 as i was hoping they'd have sorted their shit out (heard horror stories about the 6010's) but seems same problems..

                The Daytona was the next option if I can't seem to get the 6012 going.. although it only seems to need the cam/crank angle sensors for start up so even without them connected you can usually get it started 1 in 4 times..

                Ah well fresh set of plugs this weekend and fiddle it some more.

                Comment


                  #9
                  16* is on the lowish side, mine liked 26* , and no timing retard on start

                  But as above, use a timing light and check it

                  Make sure you are actually commanding 16* and don't have any baselines.

                  Most importantly have at 2 big grounds off the engine

                  Sent from my HTC One M9 using Tapatalk
                  Originally posted by 50RTD
                  Dave, have you uploaded the data from the carby?

                  Comment


                    #10
                    Fresh set of plugs.. still didnt want to start properly...

                    Did up a fresh ignition map with some info I got of fellow PFer Nitrane and it started multiple times on the first go and settled into a nice idle. Might even be game to take it for a drive soon.

                    Still need to get a timing light but fiddling in mean time.

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                      #11
                      Glad it's slowly progressing.

                      Should of whacked a memcal in it and got Bill Lee to tune!
                      Originally posted by brasher
                      TJ is 99% African American.

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                        #12
                        Originally posted by TJ View Post
                        Glad it's slowly progressing.

                        Should of whacked a memcal in it and got Bill Lee to tune!
                        I should have left it efi probably. But where’s the fun in that!

                        I did consider a Holden lump, 215i would have been alright if they were still cheap

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                          #13
                          Vid I nabbed when testing to see if it would start or not.


                          no idea why sound isn't working.. bleh.

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                            #14
                            Drove it yesterday.. then finished the drive like this:




                            Runs rich on idle with bonnet closed..so starts to foul the plugs when sitting at lights/etc (had it pretty good with bonnet open.. didn't think to check when closed).. so waiting on some fresh plugs to arrive so it'll start up and idle then lean then lean it out (I have an AFR gauge fortunately)

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