Blown 79 Z28 Camaro Make it Better Project

Discussion in 'Project Progress' started by Bandit723, Oct 1, 2016.

  1. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    There is more to adjusting these carbs on the idle side than the idle mixture screws. "idle air bleeds"
     
  2. 80sz

    80sz Veteran Member

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    Feb 2, 2014
    Buffalo,n.y.
    Yup . 70 is on rich side. I got 73 and 75 if you want them cheap. Got some others also for hsab
     
  3. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    So worked with Pro-Systems today. We discovered that the idle bleeds were swapped in the wrong positions and created most of the rich running behavior of the engine. These folks have a in my opinion have a unique way of debugging carb/engine tunes. We did settle on 78's on both the primary and secondary idle bleeds.

    We did talk about getting the idle bleeds leaned out a bit more just for the fact that will enable a more efficient use of the idle screw circuits their take is that these should be backed out a turn and a half to two turns with there setup reason being is better fuel atomization off the line.

    From the rest of the build sheet in comparison to what the old carb has it is close. jets are spot on and the Hi air or what some folks call hsab is a thousands different.
     
  4. Twisted72

    Twisted72 Veteran Member

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    Nov 8, 2015
    New Albany, Indiana
    hopefully all that works so you can get back to the street and have some fun
     
  5. Bandit723

    Bandit723 Veteran Member

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    Should be fine maybe a little more fine tuning. Now if it would just raining so i can go out and test drive the car....
     
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  6. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    Bit more activity today. Went to fastenal and ordered some drill bits to drill out the air bleeds seems that for whatever reason i bought a bunch of blanks with the intent of doing some fine tuning. so 15 dollars of drill bits vs. looking for what i need and the cost of shipping "cost savings".

    So was able to go for a test ride cold start of the engine was great seeing i have no choke. Had to adjust the secondary float and still have a bit to do with that never seem to get this done right off the bat. Car did run out very smooth almost like my dodge truck does and is very responsive.

    Took a second look at the idle bleed jets that shipped definitely looks like they are blanks so not sure what to think? what i am looking at are not even close to a 40 jet let alone a 70. So at this point I will put the carb back to specs even though i know the idle circuit is a bit rich then lean out from there. I am good with the high speed bleeds and jets A/F was spot on and at full boost i was at 11.5 on the gauge.

    One other item we did change from the original carb was to delay the secondary's from kicking in the change did make for a better engine reponse. Seeing that i am running a low compression 9:1 engine makes no sense to open up the secondary's right off the bat all you are doing is loading the engine up with fuel but once you go WOT and produce boost look out.
     
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  7. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    Did more adjusting today. Fixed the secondary float bowl fuel level yesterday's run i did get a bit of fuel starvation when i opened up the secondary's. So took the time to figure out why i had a hard time adjusting the fuel level back up, after looking at the 4150 i took off you can adjust the float adjustment down "clockwise" to the point where the nut no longer catches not knowing this i did trash the gaskets trying to raise the fuel level so 7 bucks at the parts store and i was back in business.

    Had to adjust the four idle corners again ended settling with just short of a 1/2 turn out on the primary idle and a 1/4 on the secondary more work coming on this next week but did get the most vacuum and a steady vacuum needle with this.

    So pulled the PCV and stuffed a K&N filter in it's place and went for a couple of all out WOT throttle runs "feeling more confident" so went for the 1/8 miles runs where it is safe to do so out here. Backed out the BTM advance to the number 1 setting "I am currently set at the dist at 28 all in" and let it rip from a rolling start if i hit this thing in 1st gear all i do is roast the tires so hit second and pulled of 95 mph on both runs. distance is 0.1 miles

    All i can say is this thing did let loose holy smokes. so the first run i did look at the A/F reading and read 11.5 i am happy with that. Second run was more interested in the shift points.

    Overall i am happy with the new carb purchase has made a noticable diff.

    Picture of the bowl adjustment. Go to far clockwise and the adjustment nut no longer catches.

    DSC_0794.JPG
     
  8. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    So did a bit more driving today and a long one. Car is a bit rich still in my opinion but the startup this morning "was 50 out" was good. couple of taps on the throttle and the engine did idle up well. Car did run smooth and am happy with that.

    Pulled a plug just to take a look not the worst but still am looking for the golden brown.

    DSC_0795.JPG

    Made a mess of the garage floor when running too rich

    DSC_0796.JPG
     
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  9. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    So played around with the air bleeds again today and made good progress. Put the bleeds back to the specs that it was built with and as expected it was limited as to how lean or how far i could back the idle screws out less that a 1/4 turn gave me 11.8 on the a/f meter.

    Drilled out some new air bleeds and went 76 on the secondary side 86 on the primary side. This did work out nice with the idle screws still set from before the a/f went up to 15 and allowed me to open up the idle screws to bring the a/f back down to 12.5. Very happy with the results.

    Tools used - did purchase the drill bits from Fastenal and are numbered bits 44 - 50.

    DSC_0797.JPG
     
  10. Bandit723

    Bandit723 Veteran Member

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    Oct 1, 2016
    Waupaca WI
    So this day is bringing more stuff. Was hanging out in the Garage going over some of the next steps on the car Garage door was open and a 66 impala rolled into the driveway. Car was awesome and well done. So two guys step out and were interested in the car "note to myself before i forget names are Pat and Tony" and do live in town.

    Any ways they started looking over the car asked a few questions and immediately offered me 25 grand for it. I said i was not ready to sell and Pat did pick up on that but both left the offer on the table.
     

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