EMPI "Webbers"

[DjEep]

Art, the PO of my new '68, just bought a pair of EMPI "webber" 40's for his '72. I was scared when I saw the "EMPI", so was he. The shop he ordered from just called 'em "Webbers" on the phone I guess.

We got them on, got it running, but we are both noobs in the world of duals.

Anygiblet, what are the adjustments that need to be made? We got them on, synced at idle, and seem to have the mixture dialed in as best as we could get using the ol' turn in, then back out method. What's next? Jet sizing? He said that after I left today he up-sized the Idle Jets from 52 to 55 or 57, I forget, per his local VW shop's recommendation.

Oh yes, the issues at hand are backfiring through tailpipe and carbs, mainly at steady partial throttle and decel after holding throttle. Also need any knowledge as to the voodoo of the linkage, like getting them to open in "perfect" sync, as the right one always seems to want to open sooner.

He took it for a trip around the block and said it would go pretty fast if he floored it, and stumble and cough at partial throttle. I say he should be nicer to his bus and not floor it uphill or even test drive it when we already know the carbs are poppin' like so many housing bubbles. But his test drivin' style has always been to floor it through the gears, short shifting and trying to climb 10% grades in fourth, you know, just to put it through its paces...

I hope for Maybelline's sake he didn't drive her like that all the time.

[Amskeptic]

EMPI "webber" 40's for his '72.
issues at hand are backfiring through tailpipe and carbs, mainly at steady partial throttle and decel after holding throttle.

Huge unknowns here. EMPI "Webber"? Don't make me puke!
Weber is Weber, and EMPI is crap.

Generally, you have an unsnchronized symptom here.
Remember that when you adjust one side to match the other, the other side *changes* as a result of rpm changes from the link adjustment. So you have to re-check the reference "master" carb and go back to the "slave" carb a couple times back and forth.
Mixtures, you really should set all screws at a base line average (just count each screw to bottom (your number will have to be fractionalized and decimaled 1 3/8 turn is 1.375 add all four, divide by 4, make each screw the same, then, with a properly Airflow Sychronized Warm Engine, you may check mixtures with a subtle rpm drop method.
Please note too that the intake manifold-to-head gaskets and flanges can be a real problem with cheap Chinese crap.
Colin in your area this summer

[DjEep]

yeah.... I wasn't to excited when I saw that name on 'em.... Guy at the shop

Anywho, I'm confused. Pretend I'm dumb. Shouldn't be too hard, since I am, at least when it comes to carb syncing.

Start simple. Which one is the Master? Whichever one I start on?

What do you mean by "RPM changes from link adjustment"? Do you mean the change in vacuum that happens in one carb because your adjustment on the other changed the RPM?

What does it mean, and what do you do, if one barrel is pulling more than the other on the same carb?

Is all this semi-moot if he hasn't set his valves since he got his bus? I assume that a barrel-per-cylinder setup would be more finicky over valve issues than a single. Or less? I dunno...

I'm extra cornfused about the fractalized decimators. I'm good with math, but don't quite catch the context.... What do I count? Turns from where to where and divide by huh?

Thanks for puttin' up with my Palin-level ignorance.

[vdubyah73]

You want the down links angles to be as close to identical on both sides as well as close to vertical. Like this !-----------! not like this \-----------/ There will be a little slant to them. Cylinder tin sometimes needs trimming, it can interfere with the manifold to head seal. Were the brand new carbs cleaned out before ass'y? I think they pack 'em with dirt. Getting the downlinks squared away was the second hardest part for me. The first hardest part was realizing that the guys over at thesamba were right. The stamped tin air filter ass'y suck dust right thru them. A cast aluminum linkage/air filter ass'y works best. CB jet doctors are a cheap insurance as well.

some good info here.

http://www.aircooled.net/gnrlsite/resource/articles.htm

[dtrumbo]

Everything Bill said and this site has really good info as well.

http://www.carburetorclinic.com/weber_tech.htm

[chitwnvw]

Everything Bill said and this site has really good info as well.

http://www.carburetorclinic.com/weber_tech.htm

That Harney site is excellent. Read and learn, infamous one.

[Amskeptic]

Start simple. Which one is the Master? Whichever one I start on?

Yes!
But you can pick the throat that is:
a) pulling the most air as your master if the idle is too low.
b) pulling the least air, if your idle is too fast.

What do you mean by "RPM changes from link adjustment"? Do you mean the change in vacuum that happens in one carb because your adjustment on the other changed the RPM?

Yes!

What does it mean, and what do you do, if one barrel is pulling more than the other on the same carb?

see below!

Is all this semi-moot if he hasn't set his valves since he got his bus? I assume that a barrel-per-cylinder setup would be more finicky over valve issues than a single. Or less? I dunno...

Yes!

I'm extra cornfused about the fractalized decimators. I'm good with math, but don't quite catch the context.... What do I count? Turns from where to where and divide by huh?

Sorry. Just turn them all down whatever and back out an equal amount as suggested (1 1/2 turns for fako Webber?) in your average manual. I was giving you the method when you want to equalize all carbs to your current overall mixture.

[DjEep]

Sweet! Art found a good article on 'em too, which covered a lot of this stuff.

No, we didn't clean them very much, probably half the problem.


As for the linkages, I tried vertical and all sorts of angles, but it still seemed like the right one opened slightly sooner. Probably a symptom of a shitty linkage.

[Amskeptic]

As for the linkages, I tried vertical and all sorts of angles, but it still seemed like the right one opened slightly sooner. Probably a symptom of a shitty linkage.

I don't worry about the opening variation. If your left carb, for example, is adjusted already slightly more open to equalize idle airflow, then it stands to reason that the right carb is "lower" and gets yanked sooner.

It is true, however, that it is easy to get screwed up chasing things in the wrong order.

Synchronize your idle air flow with linkages disconnected, yes. Then don't worry about anything just follow the rules, rough-in your link lengths so they both snap onto the throttle levers equally, then synchronize the high speed airflow with your links at 2,700-3,000 rpm with the throttle cable held in place by non-human means. Be subtle, it is easy to freak yourself out with an engine that starts racing. If it gets above 3,000 rpm, re-position the throttle cable holder device and re-synchronize.
Wear ear protection if loud sound makes you feel harried.
Colin

[DjEep]

Wear ear protection if loud sound makes you feel harried.
Colin

A-hem... "DJ" Eep... Loud is my middle name.

But seriously, I do need to protect my ears, they are my livelihood, so that's a good call.

[dtrumbo]

... with the throttle cable held in place by non-human means.

This is really important. This non-non-human couldn't hold the throttle steady enough to really do it properly. I've since realized we should have used a non-human clamp, etc. instead of me trying to hold my foot steady.