G
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·I made a good start at tuning
I made a good start at tuning in my 79 512BB today using the techiniques discussed by JRV and David Feinberg in prior threads. Timing was right on the money. The initial carb sync check was pretty good with no throat being off by more than 1/2 to 3/4 of a number. Actual numbers were 5 1/4 to a high of 6 (more on the 6 reading later). To make a long story short, everything synced in pretty good. I only had to make a few very minor adjustments carb to carb. So far so good.
I started adjusting idle mixture with cylinber 1, which is the right front most forward cylinder using the Gudson Colortune. For a novice like me this simplifies things quite a bit as my experience factor is zilch. (I have this impression that the Colortune is a good equalizer among novices like me but that the the ear and experience takes quite a while to become a good tuner).
Anyhow, I get to the left rear carb which comprises cylinders 7,8,9; Colortune will not show a color. I can see a spark, but no color.
OK, onward to to the left front, cylinders 10, 11, 12; no problem here. Basically aside from the left rear carb all the idle mixtures are within plus/minus 3/4 turns. They are all about 2 1/2 turns open.
Back to the left rear carb, cylinders 7,8,9. After a number of tries here is where I am. I opened the idle mixtures to 7, 8, 9 ANOTHER 2 or 3 turns. OK, some progress 7 and 8 are set however the idle mixture screws are now out about 4 to 5 turns. No matter what I do cylinder 6 will not not adjust to any color. I can see the spark, energy is getting there, the fuel mixture at idle is not.
Commander (wife) ordres all stop. It's time for dinner and miller lite.
Ok, guys, here is where I am and my thoughts.
I have a problem with my left rear carb. Cylinders 8, 9 have their idle mixture screws open way too far and cylinder 7, though I can see a spark with the colortune, appears not to have any "gas" at idle.
A couple piecies of additional of information. First, remember the high reading of 6 I had with the sychrometer? This occurred in cylinder 7, the one that is the problem. Second, when I examined all the plugs they all looked good except for cylinder 7, which looked "newer", not oily, not grayish but just newer. Third, when I rev the engine lightly to 3,000rpm with the colortune in the suspect cylinder 7 it goes blue suggesting that it is not a cylinder problem but an idle circuit carb problem. I have not done a compression check yet because I suspect a carb problem.
OK, here is what I think is happening. I think there is an idle circuit jet issue with the LR carb. When I look down the throats, the position of the throttle plates in all the carbs are dead on.
How do you clean the idle jets? Are there 3 per carb, Something isn't right here? Am I way off base?
Sorry about the length,
Drew
I made a good start at tuning in my 79 512BB today using the techiniques discussed by JRV and David Feinberg in prior threads. Timing was right on the money. The initial carb sync check was pretty good with no throat being off by more than 1/2 to 3/4 of a number. Actual numbers were 5 1/4 to a high of 6 (more on the 6 reading later). To make a long story short, everything synced in pretty good. I only had to make a few very minor adjustments carb to carb. So far so good.
I started adjusting idle mixture with cylinber 1, which is the right front most forward cylinder using the Gudson Colortune. For a novice like me this simplifies things quite a bit as my experience factor is zilch. (I have this impression that the Colortune is a good equalizer among novices like me but that the the ear and experience takes quite a while to become a good tuner).
Anyhow, I get to the left rear carb which comprises cylinders 7,8,9; Colortune will not show a color. I can see a spark, but no color.
OK, onward to to the left front, cylinders 10, 11, 12; no problem here. Basically aside from the left rear carb all the idle mixtures are within plus/minus 3/4 turns. They are all about 2 1/2 turns open.
Back to the left rear carb, cylinders 7,8,9. After a number of tries here is where I am. I opened the idle mixtures to 7, 8, 9 ANOTHER 2 or 3 turns. OK, some progress 7 and 8 are set however the idle mixture screws are now out about 4 to 5 turns. No matter what I do cylinder 6 will not not adjust to any color. I can see the spark, energy is getting there, the fuel mixture at idle is not.
Commander (wife) ordres all stop. It's time for dinner and miller lite.
Ok, guys, here is where I am and my thoughts.
I have a problem with my left rear carb. Cylinders 8, 9 have their idle mixture screws open way too far and cylinder 7, though I can see a spark with the colortune, appears not to have any "gas" at idle.
A couple piecies of additional of information. First, remember the high reading of 6 I had with the sychrometer? This occurred in cylinder 7, the one that is the problem. Second, when I examined all the plugs they all looked good except for cylinder 7, which looked "newer", not oily, not grayish but just newer. Third, when I rev the engine lightly to 3,000rpm with the colortune in the suspect cylinder 7 it goes blue suggesting that it is not a cylinder problem but an idle circuit carb problem. I have not done a compression check yet because I suspect a carb problem.
OK, here is what I think is happening. I think there is an idle circuit jet issue with the LR carb. When I look down the throats, the position of the throttle plates in all the carbs are dead on.
How do you clean the idle jets? Are there 3 per carb, Something isn't right here? Am I way off base?
Sorry about the length,
Drew
