Jump to content


Photo
- - - - -

Weber tuning issue A14


  • Please log in to reply
28 replies to this topic

#1 Dirtyowlnumber4

Dirtyowlnumber4

    Advanced Member

  • Members
  • PipPipPip
  • 105 posts
  • Location:Silver City NM
  • Cars:Chevrolet S10, Cadillac DeVille, Datsun B210, VW Super Beetle

Posted 23 January 2018 - 01:08 PM

I have been following the Weber tuning guide up above this, I just finished sealing all the vacuum leaks I had today as well as all the prerequisites to actually tuning the carb.

The problem I'm having is if I turn the air mixture screws out at all, the car stops running. I seen able to get it running all right by screwing around with the idle mixture screw, but it seems like it has more to give. Running a bit rich for sure

Edit: sealing all the leaks also had made it backfire out of the carb occasionally



#2 Doctor510

Doctor510

    Senior Member

  • Senior Member
  • PipPipPipPip
  • 681 posts
  • Location:Mesa, AZ
  • Cars:Many 510's

Posted 23 January 2018 - 05:53 PM

Turn the idle speed up a bit and turn the A/F mixture screw IN slowly, check your timing  10-12* BTDC at idle.



#3 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,898 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 23 January 2018 - 05:55 PM

32/36? I don't know what you have without going back through all your posts.
 
Try setting the engine up first. Sealing any vacuum leaks is a start but correct timing, valve lash, good ignition/strong spark are also needed.

 

https://www.racetep....eber-carbs.html
 


Posted Image

#4 Dirtyowlnumber4

Dirtyowlnumber4

    Advanced Member

  • Members
  • PipPipPip
  • 105 posts
  • Location:Silver City NM
  • Cars:Chevrolet S10, Cadillac DeVille, Datsun B210, VW Super Beetle

Posted 23 January 2018 - 07:42 PM

I tried holding the throttle at ~2000rpm maybe and as soon as I turn the screw out at all it will still kill it. Haven't checked the spark, but all ignition components are brand new. I haven't checked the valve lash I'll have a look at that

I believe the timing is at 12 or so I'll double check that too I heard it was good to run at 14° with these carbs

Engine is a stock a14 sorry

#5 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,898 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 24 January 2018 - 06:42 AM

https://www.racetep....eber-carbs.html

 

You need to go through all of the above. If valves are not set or timing wrong it can alter the manifold vacuum and make tuning the carb a waste of time. You'll never get it right is there is already an underlying problem.


Posted Image

#6 Dirtyowlnumber4

Dirtyowlnumber4

    Advanced Member

  • Members
  • PipPipPip
  • 105 posts
  • Location:Silver City NM
  • Cars:Chevrolet S10, Cadillac DeVille, Datsun B210, VW Super Beetle

Posted 25 January 2018 - 10:36 AM

It occurred to me that  don't know what I'm doing. 

 

g8VK6i6.jpg?1

So from what I understand, this^^ screw just lets in more or less fuel at idle. I can use this one to seemingly make it richer or leaner, but it also seems to work alright within an entire turn, and no matter where I put it the throttle hesitates or backfires from the carb.

 

 

ULpAWiK.jpg?1

This is the real mixture screw right? and theres one on the other side for the other part of the carb. If i try and goof with this one at all the engine ceases to function, even if I'm holding it at 300rpm.

 

 

Valves seemed good, no real play between the rockers and the rods. spark seems fairly strong. Timing is at 13 degrees. Couldn't find any new vacuum leaks.



#7 Doctor510

Doctor510

    Senior Member

  • Senior Member
  • PipPipPipPip
  • 681 posts
  • Location:Mesa, AZ
  • Cars:Many 510's

Posted 25 January 2018 - 10:49 AM

It occurred to me that  don't know what I'm doing. 

 

g8VK6i6.jpg?1

So from what I understand, this^^ screw just lets in more or less fuel at idle. I can use this one to seemingly make it richer or leaner, but it also seems to work alright within an entire turn, and no matter where I put it the throttle hesitates or backfires from the carb.

 

 

ULpAWiK.jpg?1

This is the real mixture screw right? and theres one on the other side for the other part of the carb. If i try and goof with this one at all the engine ceases to function, even if I'm holding it at 300rpm.

 

 

Valves seemed good, no real play between the rockers and the rods. spark seems fairly strong. Timing is at 13 degrees. Couldn't find any new vacuum leaks.

NO! That is the idle jet holder, DO OT remover it unless you are cleaning the carb guts.  First picture shows the air/fuel mixture at idle.  IN is leaner and 

 

OUT is richer.  Idle  speed screw is attached to the linkage on the throttle shaft.  What is the clearance between the heel of the cam lobe and the top of the rocker?



#8 Dirtyowlnumber4

Dirtyowlnumber4

    Advanced Member

  • Members
  • PipPipPip
  • 105 posts
  • Location:Silver City NM
  • Cars:Chevrolet S10, Cadillac DeVille, Datsun B210, VW Super Beetle

Posted 25 January 2018 - 11:03 AM

Alright I figured it was something like that. So the only screw to adjust the mixture is that first one right?

 What is the clearance between the heel of the cam lobe and the top of the rocker?

If i catch your drift it is not much, like a mm or so on all of them I don't have a feeler gauge. If it is important to know I could acquire one and take a gander.



#9 racerx

racerx

    Senior Member

  • Senior Member
  • PipPipPipPipPip
  • 4,623 posts
  • Location:NorCal
  • Cars:71 Datsun 510 and 65 Mustang Fastback

Posted 25 January 2018 - 11:33 AM

get a dagram of the said weber and then you will see the Fuel Mixture and Idle screws. Good to know where they are at before you start turning the wrong screw.



#10 Dirtyowlnumber4

Dirtyowlnumber4

    Advanced Member

  • Members
  • PipPipPip
  • 105 posts
  • Location:Silver City NM
  • Cars:Chevrolet S10, Cadillac DeVille, Datsun B210, VW Super Beetle

Posted 25 January 2018 - 03:21 PM

This is the issue I'm having with it hesitating, seems like it happens no matter where i put the mixture screw. Seem like a problem with the carb or maybe something else?

 



#11 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,898 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 25 January 2018 - 05:12 PM

https://www.racetep....eber-carbs.html

 

You need to go through all of the above. If valves are not set or timing wrong it can alter the manifold vacuum and make tuning the carb a waste of time. You'll never get it right is there is already an underlying problem.

 

Carb adjusting is last. All the above needs to be checked and put right first. If you should have a bad valve setting or timing retarded or too advanced, you'll be fucking with the carb forever and still not get it to run right.


Posted Image

#12 distributorguy

distributorguy

    Senior Member

  • Senior Member
  • PipPipPipPip
  • 1,177 posts
  • Location:Metropolis, MN
  • Cars:77 Datsun 620, 73 Datsun 620

Posted 26 January 2018 - 09:23 AM

I'm betting the float height and drop are way out of adjustment.  Very common.  Until you do some homework on the Weber, I wouldn't advise that you do the float adjustment yourself.  



#13 Roadster-ka

Roadster-ka

    Advanced Member

  • Members
  • PipPipPip
  • 117 posts
  • Location:Vallejo
  • Cars:71 510 wagon

Posted 26 January 2018 - 09:51 AM

I don't think this is mentioned enough:IDLE mixture screw. It only adjusts the fuel air mixture at idle only. It won't fix any mixture problems above idle.

#14 Doctor510

Doctor510

    Senior Member

  • Senior Member
  • PipPipPipPip
  • 681 posts
  • Location:Mesa, AZ
  • Cars:Many 510's

Posted 26 January 2018 - 09:57 AM

It occurred to me that  don't know what I'm doing. 

 

g8VK6i6.jpg?1

So from what I understand, this^^ screw just lets in more or less fuel at idle. I can use this one to seemingly make it richer or leaner, but it also seems to work alright within an entire turn, and no matter where I put it the throttle hesitates or backfires from the carb.

 

 

ULpAWiK.jpg?1

This is the real mixture screw right? and theres one on the other side for the other part of the carb. If i try and goof with this one at all the engine ceases to function, even if I'm holding it at 300rpm.

 

 

Valves seemed good, no real play between the rockers and the rods. spark seems fairly strong. Timing is at 13 degrees. Couldn't find any new vacuum leaks.

The top picture is the one one that adjusts the A/F mixture.



#15 Stoffregen Motorsports

Stoffregen Motorsports

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPip
  • 4,021 posts
  • Location:Cool, CA
  • Cars:http://www.4wdandsportutility.com/features/rover/0611_4wd_1957_range_rover/viewall.html

Posted 26 January 2018 - 11:00 AM

Sounds like a mix of ignition timing out of adjustment and too lean. Popping out of the carb is lean, but can also be caused by distributor weights flailing around or even a fouled cap, bad plug wires, etc. You said it has new tune up parts, right? Have you checked the distributor internals?



#16 Charlie69

Charlie69

    Senior Member

  • Senior Member
  • PipPipPipPipPip
  • 6,291 posts
  • Location:Tolleson, AZ
  • Cars:1966 520, 1967 520, 1985 720 ST King Cab, 1986 720 King Cab

Posted 26 January 2018 - 02:11 PM

Is this a real Wber or is ti an EMPI Chinese knock off?



#17 Dirtyowlnumber4

Dirtyowlnumber4

    Advanced Member

  • Members
  • PipPipPip
  • 105 posts
  • Location:Silver City NM
  • Cars:Chevrolet S10, Cadillac DeVille, Datsun B210, VW Super Beetle

Posted 26 January 2018 - 03:03 PM

I don't think this is mentioned enough:IDLE mixture screw. It only adjusts the fuel air mixture at idle only. It won't fix any mixture problems above idle.

See that's what I thought, and it idles fine. Honestly it doesn't seem to mind where the screw is too much, weather it's idling or running. Yesterday i had it like 8 turns out, today I have it all the way in and I can't  tell the difference really. But the only 4 screws I can see are the idle mixture the idle adjustment and the two for the jets.

 

Sounds like a mix of ignition timing out of adjustment and too lean. Popping out of the carb is lean, but can also be caused by distributor weights flailing around or even a fouled cap, bad plug wires, etc. You said it has new tune up parts, right? Have you checked the distributor internals?

Yah its got all new igniton parts, including the distributor so I haven't done anything to that yet besides adjust the points.

 

Is this a real Wber or is ti an EMPI Chinese knock off?

It better be a real one hoho,i bought it off pierce manifolds for 450 dollars.

XSUjRYG.jpg?1

 

EDIT: the timing is at 14 degrees but it does jump around a bit. The timing set is new so I'm not sure how to circumvent that



#18 DIY 1985

DIY 1985

    Advanced Member

  • Members
  • PipPipPip
  • 79 posts
  • Location:Santa Fe, New Mexico
  • Cars:'85 Nissan 720

Posted 26 January 2018 - 08:07 PM

 So you are running a 32/36 DGV?  You are probably running rich at about 6,000' in Sliver City, the air is thinner, although that may not be the major issue.  These carbs come initially equipped with jets for low elevations. 

 

Did you have to attach a throttle linkage to the carb or did it come that way?  The primary throttle shaft should be able to, initially, move independent of the secondary throttle shaft.

 

By loosening up the seat of the primary idle jet (on the choke side) you probably are allowing an ungoverned amount of fuel into the mix.  The idle mix screw only controls the idle jet on the primary side if your idle speed screw is no more than 1.5 turns in from just touching the throttle stop, any more and you start getting fuel from the main jet, which has no similar adjustment screw.

 

Easy on finding the bottom on the idle mix screw (it can be easily damaged) then back it out 1.25 turns from all the way in.  In is lean; you want the leanest you can idle well on, but you don't want it more than 2 turns out.

 

I am guessing that your idle speed screw is more than 1.5 turns open, for whatever reason.  Yes the idle mix screw is for idle only, but idle is technically no more than 1.5 turns on the speed screw.  I can't get a good idle until more than 2 turns in with the idle speed screw in Santa Fe on my Z24 with the kit that includes a DGV, because the idle speed screw opens the throttle for the needed additional air.  IIRC, my Air/Fuel ratio gauge tells me that it is too rich, and the idle is too slow, when the speed screw and mix screw are where they are supposed to be. 

 

Spark plug reading will probably get your car tuned close enough, but, I've seen a O2 sensor go into a drill-and-clamp-on-bung for an EFI conversion, if you don't want to weld.

 

I ultimately need smaller idle, and main jets, and bigger air jets.  The DGV came with a style of idle jet dissimilar from the 'altitude' jet kit that I bought, but it may not matter because I have a DGEV that they appear to work with, or I could probably find them sold outside of a kit.  But now in January, wrenches are still too cold to comfortably handle.



#19 Charlie69

Charlie69

    Senior Member

  • Senior Member
  • PipPipPipPipPip
  • 6,291 posts
  • Location:Tolleson, AZ
  • Cars:1966 520, 1967 520, 1985 720 ST King Cab, 1986 720 King Cab

Posted 27 January 2018 - 02:00 AM

If you purchased it from Pierce Manifolds it is a genuine Weber.  I have been doing business with them for several decades.



#20 Stoffregen Motorsports

Stoffregen Motorsports

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPip
  • 4,021 posts
  • Location:Cool, CA
  • Cars:http://www.4wdandsportutility.com/features/rover/0611_4wd_1957_range_rover/viewall.html

Posted 27 January 2018 - 08:57 AM

New does not always mean correct. In the case of the distributor, new could mean you've just introduced another variable to the problem. I would remove the cap and check the mechanical advance. Twist the rotor and see if it returns. Does it have free play (movement without spring tension)? If there's any free play, it could cause the timing problem you described.