Weber probs

[RealizE]

Nope webers certainly have them....

For those who were reading/contributing to my other thread about the dgv on my car - the problem turned out to be a pinhole in the powervalve diaphragm! After 50 hours worth of ****ing around, new fuel pumps - replaced the entire iginition system$$$ etc and hundreds of dollars later - booyah. Fixed it instantly.

[[MKI-337]]

hiya guys got any recomendations as to places i can go to to get a good carb dyno tune?

i've got a 1976 MKI golf and running a 40 DOCE side draft webber.

thanks.

[TurboSuzi]

I would also be interested in knowing about the power valve. I thought that you would replace the spring with a stiffer one or can you pack out the standard spring?????

[Tuna]

You can easily put a small washer under the spring, cut a slot in it to fit . Only go one washer at a time then test. Best way to tune it (besides dyno) is to bench test the powervalve with vacum and a guage to ascertain its opening vacum (where the spring overcomes vacum, opens pv.) , then knowing that your car pulls say 10in vac at cruise you would set the pv to open at around seven , giving good throttle response (its not all about the accel pump) compared to a pv that opens at say, 5inHG .
Another problem is with a too small a carb at full power/revs , the manifold vacum will creep up to near the pvs closing point , giving a sudden lean out , so you will have to know wat your vac is at full stick. Which should be 0-3inHG any more the carbs to small.
regarding float level, all profess tuners and all literature on the subject states that a higher than standard (slightly) is considered "hi-performance" setting.
Float level is not a set in stone spec for every situation, it is a tuning variable.

[wokket]

I know very little about the detailed workings of a carb, How can the float level affect (presumably) the amount of fuel being sucked in for the same airflow???

Should have tried the washer trick while I had the inlet manifold off yesterday

[karl_2ltGC]

Originally posted by Tuna
Best way to tune it (besides dyno) is to bench test the powervalve with vacum and a guage to ascertain its opening vacum (where the spring overcomes vacum, opens pv.) , then knowing that your car pulls say 10in vac at cruise you would set the pv to open at around seven , giving good throttle response (its not all about the accel pump) compared to a pv that opens at say, 5inHG .

Can you explain what you mean by bench test?
I'm guessing this aint done on the car.

[[MKI-337]]

Originally posted by Tuna
You can easily put a small washer under the spring, cut a slot in it to fit . Only go one washer at a time then test. Best way to tune it (besides dyno) is to bench test the powervalve with vacum and a guage to ascertain its opening vacum (where the spring overcomes vacum, opens pv.) , then knowing that your car pulls say 10in vac at cruise you would set the pv to open at around seven , giving good throttle response (its not all about the accel pump) compared to a pv that opens at say, 5inHG .
Another problem is with a too small a carb at full power/revs , the manifold vacum will creep up to near the pvs closing point , giving a sudden lean out , so you will have to know wat your vac is at full stick. Which should be 0-3inHG any more the carbs to small.
regarding float level, all profess tuners and all literature on the subject states that a higher than standard (slightly) is considered "hi-performance" setting.
Float level is not a set in stone spec for every situation, it is a tuning variable.

wow i know theres heaps of info i can learn in there somewhere but im not carb literate enough to know what ur saying.

whats HG?

in my case i have a 40 side draft webber feeding a 1.6L 8V single cam MKI golf. and hints u can give me on tunning this set up?

MUCH thanks.



webber PIC

[Tuna]

Wokket, re float level,to put it simply the fuel has a shorter path to travel from emulsion tubes (in which the fuel sits at same level as bowl) to the venturis and into the airstream, when the level is higher. The fuel is 'picked up quicker & easier' by the vaccum, this can help if the carb is old/worn., also slightly richens the mixture.but
dont rush out & raise it if youve got no response problems.
A PV bench test is up to your own ingenuity,maybe make a small plate to bolt the PV to then apply vaccum (from another idling car) to other side with a guage then a bleedertap to vary the vac level reaching the pv.
See, with Holleys its easy, you just buy a PV in particular rating, with these webers however you must tune your own.
mk1337, in.Hg. is measurment of vacum .
Vaccum is high at idle and cruise (10-15in.Hg.) , vac is low at wide open throttle (0-3in.Hg.) If you are tuning your PV you must know what your motors figures are .
Re the 40sidedraft, that is too good a carb to be doing 'diveway tuning', the very best results will come from a dyno session or at least a tailpipe A/F test on the road (cheaper). That carb should need little sorting as its well sized for the motor, others like Karl? 2.6L with smallish 32/36 will need PV attention definetly.
cheers

[karl_2ltGC]

Tuna...any recomended weber books?

[Tuna]

Karl, yes. Haynes Techbook- Weber Carb' Manual is good, also includes SUs and Zenith Strombergs.
Theres a couple of other books around, David Vizard does one, all good.