Tuning a Weber 32/36

[Spades]

well, what I have read about fuel mixture says that at idle and low RPM, the timing needs to advance in order to cope with lean conditions...as vacuum goes away, the advance drops, and the timing retards in response to more fuel dumping in...

 

ported vacuum is something they came up with for emissions sake in the late 70's so that they could get some advance back at higher RPM's.

 

 

maybe this is wrong, but thats what I have found in my research. if thats the case, then 0 vacuum at idle, and then tons of advance when you hammer the throttle would make the car backfire and detonate, in theory.

 

So far, thats been what I have read and experienced. at one point i ran no vacuum advance, and cranked the dizzy to 20 degrees. it had trouble idling, but ran better with throttle than when i had the vacuum advance plugged into the weber....cause technically, even when my timing was at 10 degrees, the vacuum advance and the slight mechanical advance cranked it far beyond 20 degrees.

 

i dunno, maybe someone else can say if I am right or wrong.

[mklotz70]

Please don't take this as an attempt to be confrontational....this is a sharing of ideas and research for the education of all reading this thread.

 

 

 

My reading so far this morning has pretty much supported my comments......exceptions being, radical cams and high performance race engines. They also said it can vary between different engine types....but the ones that run better with manifold vac are the oddities.

 

http://www.highperformancepontiac.com/tech/vacuum_advance_tech/index.html

 

http://en.wikipedia.org/wiki/Ignition_timing

 

http://www.stoveboltengineco.com/howto/vac.htm

 

 

There were a bunch of engines...mid 80's?....typically toyotas if I remember right....that ran manifold vac to the dizzy....but, the advance mechanism was set up differently. The constant vacuum worked against a spring(or against a ported vac signal) and held the vac adv retarded...unitl the throttle started to open....as the vacuum disappeared, the spring advanced the dizzy(if using a ported signal, the ported signal would pull it advanced as the manifold vac signal went away). I would think this method would give a longer, possibly more consistant advance signal to the dizzy. But....we're dealing with datsuns and they use ported vac advance.

 

Keep in mind too, that the carbs weren't designed to be on/off. They try to vary fuel mixture across a broad range of rpms and load conditions. These cars were all designed to be daily drivers...not race cars....so the emphasis was placed on smooth, comfortable operation with good power and good economy. Their primary concern wasn't the WOT(wide open throttle) condition. 98%, or so, of driving is everything but WOT. Even tracking racing doesn't involve on/off gas pedal movements. Carbs are a mechanical compromise of all conditions.....if you want perfection at all points.....switch to a fuel injected setup with a tuneable ECU. :) Everything I've read about webers, specifically the dgv, says that it doesn't not respond well to the throttle getting "stabbed". It much prefers a more controlled transfer to WOT.

 

 

I did learn more about how the lean mixture burns more slowly than a rich mixture.....which would support richening up the idle mix so that it responds better as you come off idle. That way you wouldn't be starting from a borderline lean condition and go into a more lean one. You'd start a bit rich so that the off idle, lean dip would not be so severe.

 

 

Isn't this where DatzunMike pops in with the definitive answer?? :)

[steve g]

everytime i have seen this problem on a DGV its an accelerator pump issue.... Make sure the rods are working the pump plunger properly and check in the carb to make sure its spraying fuel . The acc-pump ports are very tiny and are L shaped in one spot.... very prone to plugging up .... even on a new carb

[Spades]

MK, I don't take it as confrontational at all, just trying to figure out whats going on cause there is soooo much info out there, and a very small portion of it is actually correct.

 

if all else fails, at my shop we have a retired engineer that likes to come over and have a cup of coffee and shoot the breeze. he worked as a mechanic and engineer for the air force for many years and coninued his career after the military. I can get some definitive answers from him tomarrow.

 

in the mean time, perhaps some other ratsuners will have more input on the timing subject.

 

the accelerator pump is working great, I have watched the carb function with the air cleaner off, and so has all the mechanics and other people I have shown. there is a slight delay before the secondaries dump in, and because it is running lean cause the primary jet seems too small, a stab of the throttle gives the car a second or two of lean sag before the secondary gets enough fuel to get going.

[mklotz70]

found the page again..

 

http://www.theautoist.com/weber_carb.htm

[hogboy52]

I have been following this along for some time as it covers many of the problem areas I have come across.

But the first question I would have to ask is why do you insist on the ability pop the throttle?

When the secondary of the Weber opens there is a volume of dead air that contains no fuel and empty fuel feeders. If the throttle is banged open the air flow is disrupted, the manifold vacuum drops, the timing retards,the primary flow slows, the the motor stalls.

With the stock carb, the secondary opening is dependent on the manifold vacuum level and not the foot pressure.

Also with SU carbs there is a damper valve which can be tuned with different weights of oil.

I know little of four barrel carbs, but I think they all have some sort of leveling system.

The Weber people make a simple, tune-able carb and expect you to educate your foot to its abbilities rather than bunch of add-ons.

If you must have instant punch at all speeds, you would want a non- progressive, 2bbl.

As to timing, there are many systems. The1600 Porsches of the 60's had no vacuum advace, but only mech. from 5deg. to 35deg @3000rpm.

My '52 Harley is allways at 35deg except when kick-starting, just like model T's.

I would add that two of the three dzzy's that I have tried lately, the vacuum cans leaked. Makes for crappy timing.

[bonvo]

thats just the nature of the beast the accel pump just cant keep up when you open the secondary

 

its because the accel pump isnt able to dump enough fuel to compensate for thr secondary being opened at the low rpm this isnt a issue with the carb it is a issue of throttle control this is what i have found to work the best

 

when your running the motor at anthing below 3k you want to be on the primary after 3k the primary will be topping out then you can stab it and open the sedcondary

 

the primary then acts momentarily as the accel pump for the secondary

 

the secondary has its own return spring with practice you will be able to feel when the secondary opens the pedal will get a little stiffer when you hit the secondary

 

it is all a feel thing for me i have found the best way to make it perform is simply stay on the primary untill about 3k if you want to whip a doughnut get a rolling start untill your at about 2k crank the wheel and stab it it will break loose with ease to spin the wheels dump the clutch at about 2500 and just hold it

[mklotz70]

here's what you need! If it weren't for the fuel mileage, it would be fun to play with it!!

 

http://www.pegasusautoracing.com/productdetails.asp?RecID=6942

[Spades]

well, you guys may want throttle control, but I intend to change the jet and do what I need to do to the carb to get better response out of it. can I just never floor it? yes, that is a option...but one I wont be considering :D

 

I understand your points, and if you guys are fine with lower RPM lean sags, then good for you! I would like to have clean throttle response, regardless of how the throttle is pressed or at what RPM.

 

differant strokes for differant folks.

 

either way, I am still getting conflicting stories about vacuum advance, so I will do some more testing, and talk to that engineer if he swings by tomarrow.

 

EDIT: the new distributor I am running doesnt have a vacuum leak by the way, that was the first thing I checked weeks ago, and it is what made me by the new dizzy in the first place.

[banzai510(hainz)]

let us know the fix.

I think the weber is goo and most likely is jetted for 90 percent of the 4 cylinders on the road.

 

Most webers have a bog is PUNCHED HARD ,like your driving up in rpm then you punch it before it get enough vaccum it will bog.

 

If you do have like a 2 sec BOG then maybe something is wrong for sure.

 

if power brakes make sure no leak there in the brake diaphram/hoses ect....

 

 

weber was on STRIKE a few years ago maybe the carb is bad. swap out another if possible. but I think timming and adjusting the carb mixture should be all that is needed. maybe run the old distributor again.

 

only other thing I can think of is when one puts the hex nut on the trottle shaft linkage the butterflys/plate could bend if tightening it up too much!!!!!!. Puts a torq on the throttle shaft giving a more open condition thus looseing vacuum.

 

 

Im also hoping the new distributor was a drop In and the rotor was in the exact same spot as the orginal.like pointing in ther same exact location.

Edited November 9, 2009 by banzai510(hainz)

[jrock4224]

i have a question why cant weber make a carb that bolts on and works ......mine have both been fits and have used many 32/36 and all have experienced eihter jet or float problems... i wish in my business i could sell problems and get away with never having to deal with it.......my favorite responses are the ones that say vague this and vague that its simple.....done .....

[DISLEXICDIME]

Well did you figure it out?

[Laecaon]

Well did you figure it out?

 

necroposting much?

[DISLEXICDIME]

So I take that as a no.

[sinner720st]

uh, i solved the problem on my carb (32/36 dgv, on z 24) ITS THE "synch link" i got it from pegasus. fifty bucks, it does wonders

 

 

 

makes both throats open in synchronous fasion. comes with dual accelerator jet head, linkage, and some small new hardware for the throttle shaft.

 

 

no hesitation at all, no bog, better lower end torque, better acceleration, so far a little less fuel milage, but thats probably due to me railing on it everywhere i go

[DISLEXICDIME]

I have a dual accel pump jet I wonder if I should try it

[yello620]

uh, i solved the problem on my carb (32/36 dgv, on z 24) ITS THE "synch link" i got it from pegasus. fifty bucks, it does wonders

 

makes both throats open in synchronous fasion. comes with dual accelerator jet head, linkage, and some small new hardware for the throttle shaft.

 

no hesitation at all, no bog, better lower end torque, better acceleration, so far a little less fuel milage, but thats probably due to me railing on it everywhere i go

 

Just out of curiosity, i checked out that pegasus racing site you ordered from. They have some cool stuff, several items that i had not seen before. However, i was dissappointed in their selection of weber air filters.

[DISLEXICDIME]

Jason you have any 165/180 main jets

[sinner720st]

Just out of curiosity, i checked out that pegasus racing site you ordered from. They have some cool stuff, several items that i had not seen before. However, i was dissappointed in their selection of weber air filters.

 

some pretty cool stuff indeed, i agree on the filter selection, it kinda seems they cater mostly to pinto racers, and karts... they do have air horns for the dgv though (pretty pricey)

 

 

 

right now i have a stumble at part throttle, just off idle. im messing with the idle jets to dial in the progressive circuit, i started going bigger (65 primary idle, 70 secondary idle), then checked plugs, turned out very black, went back to stock (60,60), now about to drop one size (60,55)... i will let you all know how it goes

 

 

 

[Sealik]

Just out of curiosity, i checked out that pegasus racing site you ordered from. They have some cool stuff, several items that i had not seen before. However, i was dissappointed in their selection of weber air filters.

 

 

These guys could supply me with a Weber air cleaner cheaper than I could buy 1 here (Canada)...shipping included.

They also list on Ebay

 

http://www.allcarbs.com/catlist.php

[yello620]

some pretty cool stuff indeed, i agree on the filter selection, it kinda seems they cater mostly to pinto racers, and karts... they do have air horns for the dgv though (pretty pricey)

 

 

 

right now i have a stumble at part throttle, just off idle. im messing with the idle jets to dial in the progressive circuit, i started going bigger (65 primary idle, 70 secondary idle), then checked plugs, turned out very black, went back to stock (60,60), now about to drop one size (60,55)... i will let you all know how it goes

 

Leave the idle jets much closer to stock (about the 60,60), and increase the size of your air corrector jets by two sizes. Should help draw a little extra fuel when you crack the throttle and increase the vacuum.

 

 

I have several sizes of these if you want to try some.

[yello620]

Jason you have any 165/180 main jets

 

Nope, largest spare i have right now is a 155. Also have a 150.

[sinner720st]

Leave the idle jets much closer to stock (about the 60,60), and increase the size of your air corrector jets by two sizes. Should help draw a little extra fuel when you crack the throttle and increase the vacuum.

 

 

I have several sizes of these if you want to try some.

 

 

that would be awesome, i am planning on goin to rr this weekend, or wherever people end up going