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Thread: New Store Item - Weber Adapter Plate

  1. #31
    Gerry Lazo 56 190SL owner walazos's Avatar
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    Re: New Store Item - Weber Adapter Plate

    Francesco,

    My chokes are 28. I took Jim's recommendation a long time ago and reduced mine down from 32's
    Gerry Lazo
    56 190SL (6500870)

  2. #32
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    Re: New Store Item - Weber Adapter Plate

    I installed these over the weekend - replacing the adapters available from other sources. The fit and install is much easier b/c of the studs for the airlog mounting. The allen head bolts to mount the plates to the carbs is also superior to the phillip head flush mount screws needed for the previous version.

    Two thumbs up.

    Only issue - which isn't unique to the club adapters - with the thickness of the recommended Weber soft mounts (spacer w/ o-rings on both sides) and the air-log adapter there is very little space between the airlog and passenger side heater core. I may have to find a thinner option for mounting Webers. I have small pad to cushion the heater core for now but some extra space would be nice as the engine will move under load. If the next batch of mounts could be made any thinner that would help as well.
    Dave

  3. #33
    Administrator JimVillers's Avatar
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    Re: New Store Item - Weber Adapter Plate

    Dave .... We cannot make the adapters thinner because of the thickness of the bolt heads and the thickness of the vent slot. I do have an adapter that was made from 1/8 steel with the studs welded onto the plate and then the carburetor float vents fitted against a welded vent in the air log. I used that for many years and that is where I discovered the importance of the float vent to the Weber operation.
    Jim Villers
    1961 190SL, 230SL 5-speed, MGB 5-speed, Porsche 356C; 1967 Porsche 911; 1950 Jeep CJ3A

  4. #34
    Registered User totÚpt's Avatar
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    Re: New Store Item - Weber Adapter Plate

    You're right .. there's really little space.
    I have shortened a little the studs to allow the air log to get in better..
    Francesco
    Francesco
    190 SL 1961 - (ex US OZF-810)
    Sorry for my "Google" English...

  5. #35
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    Re: New Store Item - Weber Adapter Plate

    When mounting the air log, I have placed my floor jack under the oil pan and lifted the engine to get better finger clearance. I also place a hand cloth under the log and carburetors to catch the inevitable dropped washers and nuts. I think I recovered most of them. I, too, purchased the adapter plates for a Mikuni application. I can't get rid of the stumbling on acceleration. I tried this with the air filter disconnected. No improvement. Tomorrow, the log comes off. I may have to rebuild the carburetors in case the problem is sticky accelerator pumps.
    Jack English
    1960 #15229 Since 1972
    1971 MBZ 300SEL 6.3 Since 1983
    1999 MBZ 430E Factory Delivery

  6. #36
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    Re: New Store Item - Weber Adapter Plate

    See the other post. I don't want to repeat. With adapters and log off, the settings were again adjusted. Then I put 200 cc ATF and 11 gallons of clean gas and pushed it for 35 miles. The ATF mixes well with gas and adds detergent to clean inner surfaces. (I also put ATF in the 6.3 at every fill up - and there are many. That helps keep the mechanical fuel injection lubricated.) The SL was working well when I put it away.
    Jack English
    1960 #15229 Since 1972
    1971 MBZ 300SEL 6.3 Since 1983
    1999 MBZ 430E Factory Delivery

  7. #37
    Administrator wpuryear's Avatar
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    I have done a bit of searching for information on internal versus external vented carburetor bowls and found that they come in both flavors with a few even having a combination of the two.

    In the internally vented carburetor, air for venting the bowl and air for the venturi all come through the same intake and are at the same pressure. A dirty air cleaner would restrict air flow which would result in a lower pressure in the venturi. If the bowl is internally vented, pressure in the bowl is also lower so the flow of fuel through the jets would not be affected. With an externally vented bowl, the larger differential pressure would result in a richer mixture.

    It would seem to me that since there will be a difference in pressure when comparing the air log to atmospheric, jetting would have to be adjusted depending on which option you choose Ė internal or external. This would be most important when operating on the main jets since idle operation is mostly dependent on engine vacuum rather than venturi pressure drop.

    Walt

  8. #38
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    Re: New Store Item - Weber Adapter Plate

    We may have to discuss this further. Perhaps Walt is right about changing jets. I spent a lot of time trying to get these new adapter plates to work with my Mikuni carburetors. Could not get the stumbling on acceleration corrected. Went back to the adapters from Jim Miller in 1987. Car works very well with them. So, let's consider the dynamics of air flow. The sudden opening of the butterflies creates a significant partial vacuum at the air log. The internal venting of the fuel bowls then has a negative pressure at the vent, effectively a negative pressure on the fuel flow from the bowl. Jets are deprived of fuel, then stumble until pressure equilibrium. Open the vents to outside air and fuel flows unimpeded. Last week was Auto Week in Monterey. At one event I looked at several Datsuns made into race cars. All of the cars with side draft Mikunis had an open fuel bowl vent. Reason? Next, consider the surface area of the vent opening. This round hole is much larger than the adapter plate interface with the air plenum. Does this difference momentarily restrict air flow? I didn't measure cross sectional areas.
    Jack English
    1960 #15229 Since 1972
    1971 MBZ 300SEL 6.3 Since 1983
    1999 MBZ 430E Factory Delivery

  9. #39
    Gerry Lazo 56 190SL owner walazos's Avatar
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    Re: New Store Item - Weber Adapter Plate

    Jack and Walt,

    I can confirm the comments made by Walt. With the aid of my O2 sensor mounted in the header pipe I jetted my Webers with the air log and the old design of the adapter plates. I was able to get a decent idle ratio but my car went to a ratio of 10 right when the mains engaged. I could not find any jet combination that resolved this condition. When I installed the club plates my entire jetting set up including the idle jets went very lean. I confirmed that even at highway speeds the car was lean. I ended up having to change all the jets to richen the system. I have to also state that the air/fuel ratio reads with a much smaller range with the club adapters.


    I do still have a very slight stumble with the sudden opening of the throttle like Jack observed. I have ordered a range of accelerator jets and I am going to see if I can resolve this when they arrive.
    Gerry Lazo
    56 190SL (6500870)

  10. #40
    Administrator JimVillers's Avatar
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    Re: New Store Item - Weber Adapter Plate

    Jack ..... The air surge may be doing something you may not be expecting. The venturi is designed to feed fuel based on the air flow and pressure from a sudden air flow affects both the fuel bowl and the inside of the venturi so that it feeds the correct fuel based on the air flow. If you vent the fuel bowl to the outside, it will have a larger pressure differential and feed more fuel. This may be working for you by giving you a richer mixture but that is not the design. Like Gerry says, if there is a hesitation on acceleration where more fuel is needed, the correct way to add additional fuel is to change the size or duration of the accelerator jets.

    I will also say that if it is not broken (and you are happy), don't fix it. On the other hand, I do a lot of experimentation to discover the "correct" tuning because I enjoy immersing myself into stuff like this.
    Jim Villers
    1961 190SL, 230SL 5-speed, MGB 5-speed, Porsche 356C; 1967 Porsche 911; 1950 Jeep CJ3A

  11. #41
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    Re: New Store Item - Weber Adapter Plate

    Jim,

    Iím confused.

    By ďcorrectĒ tuning (changing jets), are you not effectively changing the design of the Mikunis or Webers to operate with the club plates?

    Rather than a club plate design (with external venting) that functions ďcorrectlyĒ with the respective carburetor designs?

    In my experience, Mercedes carbureted engines always ran too rich fouling plugs. Just part of their attraction. Click image for larger version. 

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ID:	30487My secretary originally bought and owned my 190SL. She complained about having to constantly change out fouled plugs to our TRW engineers. So they built her a unique spare spark plug holder that is still installed in my car. Maybe this is what you need. See attached photo.

    Have Fun,

    Coy
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  12. #42
    Registered User tommd's Avatar
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    Re: New Store Item - Weber Adapter Plate

    I am not sure how wide of a sample pool you are using when you say they foul plugs. I do not know that that would be a universal experience.
    Tom D.
    1961 190SL

  13. #43
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    Re: New Store Item - Weber Adapter Plate

    Quote Originally Posted by Jack English View Post
    ... Then I put 200 cc ATF and 11 gallons of clean gas and pushed it for 35 miles. The ATF mixes well with gas and adds detergent to clean inner surfaces. (I also put ATF in the 6.3 at every fill up - and there are many. That helps keep the mechanical fuel injection lubricated.) The SL was working well when I put it away.
    Jack,

    I would love to learn about what made you leaning towards the ATF for the purpose you mentioned. As we all know oil topics are widely discussed within the community this is a pretty interesting one to follow. I decided to go with 2 stroke oil for the same purpose with the mechanical FI in my W189. I use it for the 190 SL as well for two reasons: modern gas won't age that fast and no residue is left when the fuel chambers in the carbs dry out. Last thought on this was finally the fact that 2 stroke oil is meant to burn while ATF is meant to be heat (and burn) resistant as much as possible due to the thermo-characteristics in any given automatic transmission. Would love to hear your thoughts.

    Thank you,

    Ben

  14. #44
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    Re: New Store Item - Weber Adapter Plate

    Well, the 6.3 recirculates gas back through the tank (emission control) so, if it didn't burn I would have a tank full of ATF! This suggestion was put forth by a member of the M-100 Group years ago. In addition, a presentation last year on revival of a long dormant car included the use of ATF as a general cleaning fluid to force through all of the fuel lines and injection pump. This oil is light and contains detergent that helps open up clogged lines. I once was asked by the service manager of the local MB if I wanted the Fuel Cleaning Treatment on our new car. I replied that I used ATF in the gas and he responded, "Then you don't need it." I also add a unit of ATF to the engine oil about 50 miles before an oil change. I don't know if that helps or not.
    Jack English
    1960 #15229 Since 1972
    1971 MBZ 300SEL 6.3 Since 1983
    1999 MBZ 430E Factory Delivery

  15. #45
    Gerry Lazo 56 190SL owner walazos's Avatar
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    Re: New Store Item - Weber Adapter Plate

    I wanted to provide a update on my slight stumble I mentioned in a earlier post. I was running 0.500 accelerator jets on my initial set up that created the stumble. I ordered 0.550 and 0.600 jets. I installed the 0.550 and the stumble showed a noticeable improvement. I then swapped them for the 0.600 ones and the stumble is gone. I had my friend who is a dealership mechanic at Honda with 30 years experience drive the car and he noticed a definite improvement with the larger jets. He was my co-pilot during my tuning process. He was very impressed on how hard the car pulls when you put your foot to the floor. We started to speculate that we know a too lean jet will cause a stumble but would a too rich of a jet create the same condition. Has anyone experienced the effect of a oversize accelerator jet?


    The next size I see in stock is 0.700 I am tempted to buy the set of 4 to see if I can make the respond better on a quick throttle or create a stumble.
    Gerry Lazo
    56 190SL (6500870)

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