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weber ntuning saga continues

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hondo402000

hondo402000

Darth Vader
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Ok guys, tuning webers is an art not a science, I got the weber book, read it like the bible, and every thing I do has the opposite effect as to what the book says, I have an AF meter that I run, last run it was running rich, but still stumbles around 3000 rpm, so I go from 115 main jet to 120 guess what the AF ratio goes from 11.5 to 12.5 then go up to a 125 main jet and the AF ratio goes up to 13... not what its suppose to do, the stumble gets better but still there., so I go from a 180 Air corrector jet to a 175 which should make it run rich in theory in the upper ROM range but it gets leaner but runs a tad better. but still a slight stumble at 3000 to 3500 rpm.. so I guess I am just going to have to go by feel and not by the book, so I will keep trying different combinations , make notes and disreguard the book next step is to go to a 130 main jet and see what happens

stay tuned

Hondo
 
Hondo, don't get mad when I ask this, but is your timing set dead on the money and have you verified that you have no vacuum leaks of any type before you began tuning these? If either of those is an issue, it will tuning these a living nightmare.
 
hmmm, why buying for hundreds of bucks carb jets instead of an investment to a proper rolling road setup session with a much better result?

Cheers
Chris
 
Paul
yes double checked the timing, no vacuum leaks, set at 10 deg BTDC, and Chris, there is no rolling road near me and no one that knows webers so us weber guys are really on our on to sort it out, so I have an AF meter in my car and as I drive I watch the meter. the rolling road all it will do is the car is stationary but you still have to buy and change the jets to corret lean or rich conditions reguardless of a rolling road or not to get it right. Webers are not like SU or Stroms where all you do is screw in or out a nut Good news is I am getting closer to being right. and now I know why any one who has webers is very tight lipped about sharing information.

Hondo
 
You need a way to log the AF out put. Just watching it doesn't really show everything. It changes so fast you can't see it on a dial all the time
 
Why do you have your timing so retarded ? 10*BTDC at 900 rpms seems pretty retarded even if you are going by the damper marks.
 
thats what my engine guy suggested plus I dont have vacuum advance with webers, I dont have my bently manual with me either so I couldnt tell you what the book calls for

I probably need to send my distributor back out to jeff at Advance and give him all the upgrades and have it recurved too

Hondo
 
As far as watching the AF meter, it does what I need it to do which is make sure I am not running too rich or to lean, its the Inovate LM2 unit, I can put a memory card in the unit and record everything and plug it in the program on my computer, I have just been trying to get things close and figure out the flutter at 3000 RPM, once I get the webers set, the AF meter will come out and plug the bung

I also have 32 MM chokes I might switch out and see what happens. I will get it all sorted out soon enough

Hondo
 
The Vacuum Advance is not an issue whether you have it or not. There is no vacuum advance when the engine is idling even if you did have it,

As a rule you should always have your ignition timing squared away BEFORE you attempt to find a compatible carb mixture.
 
Set yes, but is it set right ? Sounds like you set it kinda retarded and as you say, the distributor was not recurved for the new engine.
Anyway once you have the timing set to that engine's sweet spot other things may more easily fall into place.....
 
every thing I am reading says 10-12 advanced, can try a little more advance and need to call jeff

hondo
 
That 14-16 BTDC sounds a lot better than 10 to me and I'm sure to PB. Your centrifugal advance, if working freely, will take care of the rest as you accelerate the engine speed.
 
Make sur your getting complete advance at the correct RPM too.
 
I talked to Jeff at Advance yesterday, I got a problem with my rotor hitting on of the post on the cap, Jeff suggested sanding the rotor down some so it doesn hit, that could be the problem with my stumble at 3000 rpm, he said it could be firing on cylinder too early, Also Jeff said I might need to have my distributor recurved, but maybe not, need to check cyliinder pressures and let him know

so got some things to do this weekend

Hondo
 
well If you have not read the other post, I went back to 30 MM chokes and my best settings, made sure the aux chokes were in the correct position, I centered the thumb wheel on my Distributor, re set the advance at 14 degrees BTDC, and reved the engine up and getting full advance, went for a drive and all is good, AF ratio ranges from 12.5 at Idle to 13.5 at WOT, stays pretty close to 13.3 to 13.5 in crusing. So now going to drive around for a while and see how it settles in, there is still a slight miss on occasion but seeing its not new and its triple webers, I dont ever think I can get it perfect. I changed the oil and filter, got all the oil leaks stopped or at least to a few drops per day is good with me, now I just need to figure out the final jet settings, some were drilled out so will make some notes

Hondo
 
MIne hit and the cap wasn't seated right. I thought it was and even checked but I was wrong.

From what little I know and read, IIRC ; @ 3K you should still be on the idle jets. Either that or you're just starting to tranfer from idle to main. Can anyone here verify that or not?

How many turns out are you on the idle mix screws?
 
At 3K the blades are past the progression holes and the pumps are kickin' in too.

With these things every jet is influenced by every other one. Change one opening and all the others are affected. Part VooDoo, part physics and part intuition.

A ~big~ clue is: not all higher jet numbers mean bigger holes. :wink:

...the numbers came as jets were produced, not necessarily as sizes were increased.

Blame th' brothers Weber. :devilgrin:
 
BTW, Hondo: The AF meter is the way to DO this properly. Well done. :thumbsup:
 
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