Ed Brock

40 DCOE chokes

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    Hi,

    I'm looking for either 6 each 33 (preferred) or 32 chokes for Weber 40 DCOE series 151 carbs. Anyone have them? Our local 240Z club mentioned I should ask the 510 people as they believe you folks use these carbs more then  240Z group. So I am.

    Thanks, Ed

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    Thank you, I had not heard of these folks.  Did you get my last message about the tuning on the z car? Did some more today, did not get the results I expected. I'm disappointed.

    Tried 50 F9 and went down on the air correctors in increments of 10. Started with 200 = A/F in the 17's (better then the last adjustments). Went to 190 = A/F in the 16's, ended with 180 A/F in the high 15's and low 16's. Motor not very responsive, sluggish, surges in lower gears, lean pops on decell. Went back to 55 F9 and tried air corrector of 210. Reason for the 210's was because last tuning, the engine had an A/F in the high 11's and low 12's. Engine is better with the 55 F9 then the 50 F9, but will not keep a steady idle. It will idle at 1,400 RPM smoothly, (A/F at 13.8 or 14.3). But with idle set at 1,000 RPM, when you bib the throttle the engine will idle at 1,400 or 1,500 RPM then will very slowly  the idle speed will drop (by it's self) and stabilize itself at 600 RPM. Rechecked for vacuum leaks, found none. Going to take out the 210's and try air correctors of 200, then reduce from there and see if the idle will return to where it was before. It was very stable at 800 or 1,050 depends on were you set it. Most time idle was set for 1.000 RPM. Have recalibrated the o2 sensor between adjustment today, just incase.

    Still unhappy with todays results. I thought we had it based on our last tuning before today. This idle thing has me wondering. A/F ratios at idle were set at mid 14's, should not be getting the results we got today. Any ideas????

    Ed

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    at what RPMs do you have those A/F ratios? I'd think your throttles are unbalanced or the linkages are binding a bit to have it slow returing to idle like that.

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    You have to tune for cruise first, then idle then WOT.

    Find the right idle jet that gives you ~ 14-16 at cruise then see if you can get 13.5 to 14.5 at idle with the same jet by adjusting the idle enrichment screws.

    Once you get this, move to WOT runs.  Find the right main and air corrector to give you 12.5 to 13.5 from 3000 to 6000 rpm under load.

     

    note: Air correctors are used only to tune WOT main system.

    Edited by 240260280
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    240260280,

    First we got the car to idle well, that did require some accel. jet changes, just enough to start the motor. Then we have been tuning for cruse, under 3,500 RPM's no load. 3 days ago we got our best tuning with 55 F9, 50 accel pump jets, with 0 bypass jet. We got a flat curve , responsive throttle, some accel. stumble, which I attributed to the rich mixture, then adding more fuel when on the throttle. By a rich mixture, I mean, we in the mid 13's A/F. We had a  great idle A/F (14.5), That is why I went to the 50 F9's, to reduce the amount of fuel. That's when thing went south. With no other changes made, the 50 F9 made a lean mixture and a poor idle and it surges at cruse (A/F went from mid 13's to 17's with just one change. Makes no sense. 

    I'm going to pull the spark plugs and make sure they are okay. Recalibrate the A/F meter and retest. I will starting with the 55 F9 and putting back in the 200 air correctors. that should get us back to our best baseline of 3 day ago. Maybe it's just me.

    Thanks Ed

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    jonbill,

    The RPM's are at cruse, 1,500 to 3,500, as little of accel. pump action as possible. The idle remained set at 1,050 RPM's. Carbs have been balanced, and rechecked, throttle linkage has been checked for a problem. Actually found a problem the other day and fixed it, one rod from the throttle rod to the carb was hanging up causing motor to idle smoothly but return to idle slowly.  The motor was running good, rich but good, idled well. Yesterday, we had a rough idle, and the wait 1-2 minutes and the idle speed will lower OR raise by it's self situation. All with one change. Puzzled.

    Please see my notes to 240260280 above for more information.

    Thanks for your input.

    Ed

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    as 240260280 said, your air correctors only have an affect at WOT. similarly , your emulsion tubes and main jets have no impact on idle and gentle cruising.
    if changing things on the main jet stack ruined the idle, it'll be because you inadvertently disturbed something else. check everything. are your jet stacks all screwed down snugly?

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    jonbill,

    Yes main jet assemblies as well as all other assembles are installed properly, meaning all parts are pushed together until they touch their respective shoulders.  You and 240260280 bring up a good thing to know about the air correctors.

    However, it is my understanding, remember I'm learning, that the main jets START being used about 3,500 RPM's and you don't have to be in WOT mode to make them work. And that there is SOME overlap between the idle jets (cruising) and the main jets starting to take over. So, what I'm trying to get out, is the idle jet (cruising) work up to about 3,000 RPM's, and the main jets take over about 3,500 RPM. In the middle, between 3,000 and 3,500 you can be using SOME of BOTH jets, idle and mains. Am I correct????

    I appreciate your help.

    Ed

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    Ed, yes, you're basically right. the main circuit is activated by air flow through the secondary venturi and a number of things affect when that transition from idle to main circuit happens - rpm, throttle opening, choke sizes, emulsion tube selection being the main ones I can think of. when I was running my triple carbs, cruising, at even 3500 (80 mph maybe?) , it was all idle jets.
    In short, its the combination of some revs *and* some throttle that will make the switch to the main circuit.
    sorry that probably doesn't help solve the problem though!

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    Hi all,

    Well when in doubt go back to the basics. Air, do you have?  Spark, do you have enough?  Fuel, again, do you have the amount you need at the carbs?

    So,   #1, check spark plugs. They were fouled with fuel. A quick clean job and ready to go.  #2, checked the throttle linkage. Took them apart, all set so there is no binding anywhere and the linkage goes smoothly back together. Checked the throttle stop screws for proper opening, they were set where they need to be, 1/4 turn from .006 clearance at screws.  #3, air, well no restrictions any where, no vacuum leaks.  #4, I left the installed 50 F9 idle jets alone and went to an air corrector of 200. Engine back running lean abit in the high 15 to mid 16's.  #5, increased idle jets back to the 55F9, air corrector remained the same at 200. Now the motor is a happy camper. Idle, cruse, drivability all back to a few days ago. That's a good thing. 

    Just as we were getting back to the shop, A/F ratios went rich. Checked the spark plugs all sooted up. Now I know they were a bit used up as we had cleaned them several time, So new plugs installed, had to reset idle A/F mixture, test drive showed at cruse high 13's to low 14's. Idle excellent at 14.5. Idle always returning to base setting. Great throttle response.

    lesson remembered?  Sometimes trying to save money by cleaning your sooted up spark plugs not worth it!!  I knew we should install new plugs every time we sooted them up, but at that time we were sooting or over heating them up a lot. I decided to just clean them in the bead blaster. New plugs cured all of our issues. The car went to the customer and he was to drive it Friday.

    Ed

     

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