 count down to driving, nothing is working HELP |
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| nycchef |
 Aug 3 2009, 07:31 PM
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#1
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mechanical moron  Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None  |
2.0 dual weber 40's, you guys know. trying to get a perfect balance on the carbs, pass side (using a spectrometer) reads 5 on both barrels, driver side reads 3 and 5 , if i adjust the throttle screw 5 and 7. have the idle at 900, timing and dwell are on. no more backfiring or popping, it actually sounds good. can't find a way over the last hump. is it a valve porblem?
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Replies(1 - 19)
| Joe Ricard |
Aug 3 2009, 08:05 PM
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#2
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
Are all the jets EXACTLY the same size?
Valves are adjusted the same Idle screws optimized for best running on all cylinders? Spark plug wires fresh Spark plugs fresh gapped the same If so then I would adjust the air by-pass screw However I suspect a partially clogged idle jet. or some crud in the idle circuit |
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| tat2dphreak |
Aug 3 2009, 08:18 PM
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#3
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region  |
QUOTE Idle screws optimized for best running on all cylinders? this was my first thought... you sync each throat, and each carb...  |
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| nycchef |
Aug 3 2009, 08:25 PM
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#4
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mechanical moron Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None |
QUOTE(tat2dphreak @ Aug 3 2009, 06:18 PM)  QUOTE Idle screws optimized for best running on all cylinders? this was my first thought... you sync each throat, and each carb... each throat 1 1/2 turns out, wires, plugs, valves, points, plugs all correct. whats the procedure for individual throat syncing joe disasembled both carbs, blew out all the circuits and jets prior to mounting the carbs, the jets are the same. |
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| type11969 |
Aug 4 2009, 10:16 AM
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#5
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Senior Member Group: Members Posts: 1,231 Joined: 2-December 03 From: Collingswood, NJ Member No.: 1,410 Region Association: North East States |
QUOTE(Joe Ricard @ Aug 3 2009, 06:05 PM) Are all the jets EXACTLY the same size? Valves are adjusted the same Idle screws optimized for best running on all cylinders? Spark plug wires fresh Spark plugs fresh gapped the same If so then I would adjust the air by-pass screw However I suspect a partially clogged idle jet. or some crud in the idle circuit A partially clogged idle jet would affect the flow of air through the carbs? How? It seems to me that throttle plate position and any air bypasses in the carb would be the contributors to the flow of air through the synchrometer (assuming the engine is running at a constant speed). Interesting . . . |
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| tat2dphreak |
Aug 4 2009, 10:21 AM
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#6
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region |
QUOTE each throat 1 1/2 turns out, wires, plugs, valves, points, plugs all correct. whats the procedure for individual throat syncing joe disasembled both carbs, blew out all the circuits and jets prior to mounting the carbs, the jets are the same. use the adjustment screws... 1 1/2 turns is the starting point. one or the other may need to go a little more or less... plus it's impossible to unscrew them the exact same.. so you may have to turn one an extra 1/8th - 1/4th to get all 4 throats equal on the sync. |
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| jmill |
Aug 4 2009, 10:24 AM
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#7
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Green Hornet Group: Members Posts: 2,449 Joined: 9-May 08 From: Racine, Wisconsin Member No.: 9,038 Region Association: Upper MidWest |
With the butterflies closed air enters through the idle jet. There is some leakage around the butterfly and small holes in the plate. But it's minimal. What Joe said above is dead on.
If you adjust the mixture screws for flow you'll screw up the best idle mixture. You can't change the air fuel mix with the mixture screws. You need to open the air bypass on the low barrel and again adjust the mixture screw. Usually it's a plugged idle circuit. Make sure it's clear before you go this route. |
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| type11969 |
Aug 4 2009, 10:29 AM
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#8
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Senior Member Group: Members Posts: 1,231 Joined: 2-December 03 From: Collingswood, NJ Member No.: 1,410 Region Association: North East States |
Interesting. Really seems like the bleed of air around the butterfly with it X degrees before closed to set the idle speed and any additional air bypass bleeds would far outweigh any air bubbling through the idle jet, but if thats what you see then thats what you see.
The throttle shaft could be tweaked too. |
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| jmill |
Aug 4 2009, 10:40 AM
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#9
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Green Hornet Group: Members Posts: 2,449 Joined: 9-May 08 From: Racine, Wisconsin Member No.: 9,038 Region Association: Upper MidWest |
A tweaked shaft will give you one high flowing barrel and 3 low. One low is most likely a plugged up jet. I'd peal it apart and blow it all clear first.
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| tat2dphreak |
Aug 4 2009, 10:47 AM
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#10
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region |
listen to jmill and joe, they know more than me. mine was on, but I thought I'd read somewhere the ind. throat might need a slight adjustment...
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| nycchef |
Aug 4 2009, 11:31 AM
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#11
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mechanical moron Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None |
QUOTE(tat2dphreak @ Aug 4 2009, 08:47 AM) listen to jmill and joe, they know more than me. mine was on, but I thought I'd read somewhere the ind. throat might need a slight adjustment... o/.k i am heading over to the car and am going to blow out the air jets and circuits again (compressed air) when that is done should they be put back completely in (closed)? |
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| Joe Ricard |
Aug 4 2009, 11:33 AM
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#12
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
You need to have an equal combustion event to have equal air flow.
Air passing over the 28mm venturi creates enough air speed to suck fuel out of the idle jet. At idle turning the screw in and out does affect idle mixture. only at idle up to 1200 or so RPM. after that the air passing over the opening throtle plate sucks fuel through the progression ports via the idle jet. after that 2500 to 3000 RPM the main jet will start flowing. My carbs are nearly dead nuts the same on air flow. However they are not stock out of the box anymore. I have reamed the idle air correction jets EXACTLY the same. I reamed the acceleration pump nozzles which were WAY off. All my idle jets were not the exact same size as measured with a ream. Now they are and it made a big difference is smoothness. Main jets and main jet air correction also got that treatment. I did some porting in the carbs too. |
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| Joe Ricard |
Aug 4 2009, 11:45 AM
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#13
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
Jets all the way in with good O-rings.
By-pass screws all the way in Idle mixture screws 1 1/2 turns out to start Then adjusted to leanest possible before engine speed drops then back out 1/4 turn. (go slow and listen for the engine to react. If you can turn in the screw past past 1 full turn from closed then you still have crap in the idle circuit passages for that cylinder. |
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| type11969 |
Aug 4 2009, 11:59 AM
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#14
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Senior Member Group: Members Posts: 1,231 Joined: 2-December 03 From: Collingswood, NJ Member No.: 1,410 Region Association: North East States |
Good to know, thanks
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| nycchef |
Aug 4 2009, 12:56 PM
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#15
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mechanical moron Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None |
QUOTE(Joe Ricard @ Aug 4 2009, 09:45 AM) Jets all the way in with good O-rings. By-pass screws all the way in Idle mixture screws 1 1/2 turns out to start Then adjusted to leanest possible before engine speed drops then back out 1/4 turn. (go slow and listen for the engine to react. If you can turn in the screw past past 1 full turn from closed then you still have crap in the idle circuit passages for that cylinder. just tried all that and blew out the idle jets and circuit,removed the linkage, set the idle @900, no change. allow me to put forth a theory when i had the problem with the valve adjustment screw stripping off on the passenger side, the balance on the drivers side was fine , since i replaced the screw and readjusted the valves on the pass side, the driver side carbs are off. could it be that i need to readjust the driver side valves, they were done before the engine went into the car. the engine hasn't been run for more than 2 hours since. |
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| Joe Ricard |
Aug 4 2009, 03:24 PM
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#16
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
I replied on the other site just for sport.
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| tat2dphreak |
Aug 4 2009, 03:43 PM
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#17
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region |
QUOTE(Joe Ricard @ Aug 4 2009, 04:24 PM) I replied on the other site just for sport. LMAO |
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| jmill |
Aug 4 2009, 10:11 PM
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#18
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Green Hornet Group: Members Posts: 2,449 Joined: 9-May 08 From: Racine, Wisconsin Member No.: 9,038 Region Association: Upper MidWest |
QUOTE(Joe Ricard @ Aug 4 2009, 12:33 PM) You need to have an equal combustion event to have equal air flow. Air passing over the 28mm venturi creates enough air speed to suck fuel out of the idle jet. At idle turning the screw in and out does affect idle mixture. only at idle up to 1200 or so RPM. after that the air passing over the opening throtle plate sucks fuel through the progression ports via the idle jet. after that 2500 to 3000 RPM the main jet will start flowing. Actually the idle jet doesn't care about the venturi. The butterfly is closed. Air and fuel are pulled into the carb due to differential pressure (read suction). The idle jet has a set air/fuel ratio. By adjusting the mixture screw you can only increase or decrease the volume of that ratio at idle. Thats what I tried to say poorly. |
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| nycchef |
Aug 4 2009, 11:12 PM
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#19
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mechanical moron Group: Members Posts: 952 Joined: 28-November 05 From: new york city n.y. Member No.: 5,202 Region Association: None |
QUOTE Actually the idle jet doesn't care about the venturi. The butterfly is closed. Air and fuel are pulled into the carb due to differential pressure (read suction). The idle jet has a set air/fuel ratio. By adjusting the mixture screw you can only increase or decrease the volume of that ratio at idle. Thats what I tried to say poorly. i guess i have to start from scratch, readjust the valves and see whats what. am ordering a new cable and cluster bushings.will i damage anything if i drive it unbalanced? i want to have a little fun amist all this crap. what does LMAO mean? |
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| tat2dphreak |
Aug 5 2009, 08:15 AM
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#20
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stoya, stoya, stoya Group: Benefactors Posts: 8,797 Joined: 6-June 03 From: Wylie, TX Member No.: 792 Region Association: Southwest Region |
lmao = laughing my ass off
no, you will not hurt it with 1/4 of your cylinders a little out of sync if you want to drive it a little... it will provide motivation too... |
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