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  #1 (permalink)  
Old 05-16-2011, 06:08 PM
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Default The saga continues or tuning woes

Hi, I think it easier to rely on the vast amount of knowledge and good faith that exists here than to continue to scratch my head at each step.So,on my current saga I changed out idle jets and holders to reduce the reversion spray over the carbs(48IDAs). I'm still not happy with my linkage ( fabricated it myself) but working on it. Current problem- set the idle screws a little high and tried to read each carb with the air flow device in order to bring them into sync.. One carb stack,in particular, is showing something very odd-I think. The readings on all are a consistent number with a bit of flux-about 5-12 on the scale. The carb feeding cylinder six sucks in a pulse pattern-I mean the needle will literally bounce between 6 and 20 each time the cylinder fires. There is no way I can make any comparisons.I set the mixture screws on all carbs to 3/4 turn off seat. That cylinder, by the way, also exhibits the most upward fuel spray.I thought it just wasn't firing but I checked the wire and plug.Any ideas what I'm seeing here and how to correct it. Thanks for the help, Jon
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Old 05-17-2011, 01:51 AM
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The bouncing reading of the airflowmeter should not be linked to whatever other problems you mention; bad link, idle secrews or jets. But, it might be linked to the reversion.

My first thoughts are:

- any leakage in the runner (from mouth of air horns down to the valve)?
- is the valve opening correctly? Lift and duration as it should? (worn knocker or whatevever)
- is cylinder vacum and compression pressure correct?

I did have a same kind of problem with 2 x DCOE once, fuel came out of one of the carbs, dripping. I think the solution to this was to connect one vacum line from each runner into a single line for brakes and dist. vacum (although I didn't get to test this). Of the 4 runners, 1 gave vacum to the brakes, 1 to the dist.

So, if you run any vacum lines from that cylinder, that may also be a part of the problem.

RS
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Old 05-17-2011, 01:58 AM
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Jon,

As Rune has said, if you don't have already add a vacuum port to each runner about -3 AN or -4 AN plumbed into an 8 in/1 out block. You can then plumb your brake booster to the 8 way block.

Can you post a pic or two of your setup?
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Old 05-17-2011, 05:57 AM
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No vacuum system in play. Mechanical adv.dist. and manifold has no place for fittings( Carbs Direct unit I bought).Could be leaks someplace. I'm learning how sensitive these carbs are to random leaks. I think I'm going to pull a valve cover and see if the lifters are working properly on that side. I can't imagine that only one cylinder got damaged or rings didn't seat properly( new build) but who knows. I'll try to post a picture of the actions tonight. Thanks, Jon
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Old 05-17-2011, 03:04 PM
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Would you believe it- wires. I thought long and hard about why fuel was spraying up from the stacks but only on three of the carbs. O.k did I forget to put rings on those pistons and other foolish things went through my mind. So I started with the cheap route since I still don't understand Webers- Put on new spark plug wires. voila! spray stopped and erratic bounce to flowgauge stopped.Some pistons just were not firing. I even wondered if the MSD box was doing the "shut down cylinders to avoid over reving but at the idle end by mistake". I feel much better thank you. Now I still need to sink these things.Regards, Jon
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