Weber jets??All who live for their triples please read this

[SuperDan]

Jon, yeah it is strange.

I have this wideband O2 monitor mounted in my car and used it to setup my jetting. It’s also kinda fun to watch 

http://www.innovatemotorsports.com/xcart/customer/product.php?productid=16164&cat=262&page=1

Right now my AFR’s are:

Idle = 12.6 – 13.0

Why?

I have no idea, I cannot go leaner on idle or it will idle rough and transition off idle creates a nice bog… I can live with it.

 

WOT = 12.2 – 12.8

Seems good to me.

 

Cruise 3000 RPM = 12.8 – 13.2

Why?

I think the multistrike ignition may have something to do with this.

Just guessing.

 

On 91 oct gas I get no pinging under any conditions.

On 89 I get pinging when the engine is nice and hot on the freeway and I bog the engine a little at full throttle.

On 87 I get pinging at any more than ½ throttle under load and I can definitely feel the loss in power.

The AFR’s above seem to stay the same regardless of the type of gas used.

 

I am starting to think that I should remove the vacuum advance (since it’s not used anyways) from my dist and lock the plate down, maybe it is a factor in this.

[JMortensen]

Jon' date=' yeah it is strange.

I have this wideband O2 monitor mounted in my car and used it to setup my jetting. It’s also kinda fun to watch 

http://www.innovatemotorsports.com/xcart/customer/product.php?productid=16164&cat=262&page=1

Right now my AFR’s are:

Idle = 12.6 – 13.0

Why?

I have no idea, I cannot go leaner on idle or it will idle rough and transition off idle creates a nice bog… I can live with it.

 

WOT = 12.2 – 12.8

Seems good to me.

 

Cruise < 3000 RPM = 14.3 – 14.8. >3000 RPM = 12.8 – 13.2

Why?

I think the multistrike ignition may have something to do with this.

Just guessing.

 

On 91 oct gas I get no pinging under any conditions.

On 89 I get pinging when the engine is nice and hot on the freeway and I bog the engine a little at full throttle.

On 87 I get pinging at any more than ½ throttle under load and I can definitely feel the loss in power.

The AFR’s above seem to stay the same regardless of the type of gas used.

 

I am starting to think that I should remove the vacuum advance (since it’s not used anyways) from my dist and lock the plate down, maybe it is a factor in this.

Weird. Well your AFRs look really good to me. I'm sure you're dialed in better than 99% of triple carbed cars out there. I think you might be right about the MSD or Crane or whatever you have throwing off the numbers below 3000. So maybe a leaner idle jet???

 

I have locked down a couple ZX distributors. I don't know if it's going to fix your problem necessarily, but I did it to reduce the possibility of timing scatter, and because the POS vacuum advance mechanism was already broken on mine (like all of them). When I pulled mine apart the reluctor had been hitting the stator for some time. The teeth on the stator were partway worn off. Not good.

[duragg]

Thanks:

I found the high idle problem when I took the carbs off to clean and check for vacuum leaks.

 

The throttle stop is mis-adjusted and when you slam the throttle down the throttle plate arm jams on to the full open stop and bends itself back a small amount. Then when the throttle goes back to idle the now-bent throttle plate arms keep the plates open a small extra amount to the point where the idle screw is all the way out and the plates are still way far open. Ok, fixed that.

 

For all the cleaning and checking on the carbs I did it doesn't change the idle pop at all. Its really only idle and just barely cracked throttle that it pops in all the cylinders. Not really out the carbs, just in the headers which are glowing red hot.

 

So the engine is either WAY lean or whacked out of timing, or stuck valves.

But it makes good power so I am not sure about stuck valves.

 

Gonna physically check TDC with a dial indicator today.

[duragg]

Found this handy "DOS" based calulator for rough estimates on Weber jetting. I found this on the Alfa Romeo website.

 

It is designed for a 4 banger with double Doubles, so I just input 1600 as the displacement (2/3s of an 2400) to simulate an L24.

 

http://www.airpowerinsurance.com/zcar/jetting.exe

[SuperDan]

Not really out the carbs, just in the headers which are glowing red hot.

Glowing headers at idle... had that happen to me on a EFI V8, it was the timing was retarded alot.

[duragg]

Ok I fixed it.

I removed the carbs and cleaned everything up, but still popped at idle.

 

My friend Joe Moriarty (Owner of Total Seal Piston Rings) said it sounded like a "Lean pop" to him.

 

So I pulled the idle jets again and cleaned them double good again.

 

SEATING::::: I took time to remove the jets and seat them lightly into the carrier, then re-installed which allows the jet to seat better in the housing. (Is this common knowledge??? I'm new to carbs.)

 

Doing this cured the lean pop and they run good now.

I still plan to buy a slightly richer idle jet, and also get the service kits and rebuild the carbs.

 

Thanks for everyone's help, this was a fun adventure.

Tj

[srgunz]

Duragg;

Reset your fuel pressure from 5psi to 3psi. That should also help.

Also make sure your exh valves are not so tight that they will not fully seat.

[duragg]

I have the fuel pressure at 5psi now and will bring back to 3.

Valve clearance is good.

Car running a LOT better.

 

TJ

[duragg]

Ok, forgive me a minute.

First an update on my Triple Weber troubleshooting and setup.

Then some emotional comments about carbs.

 

{1973 240z with L24, 5sp, Triple DCOE 40-151s with 30mm chokes, 50F9 Idles and some other jets I can not remember exactly which now..., headers, a glasspack and thats it. I bought it this way... just a toy}

 

I bought this Z as a fun driver while my '72 is in restoration.

It barely ran. I rebuilt the carbs, replaced the entire ignition system verified compression, timing, vacuum leaks etc.

 

One of the most critical things I learned from this experience is to properly "seat" the jets in the Weber DCOE carbs.

1) "I THINK" the Weber jets should be "lapped" into their seats with lapping compound to make a perfect seal. (I didn't do this, but would next time).

2) "I THINK" the Weber jets should only be lightly installed in their carriers prior to screwing down, and let the "screwing down" function set the final height of the jet.

 

I have never worked on carbs before this, so forgive me if this is old news, but I never read about it anywhere. I don't claim to be an expert of any sort, just a fan of Triples and finally got mine running smooth and even.

 

After many long days I finally got these carbs all flowing equally at idle and pulling strong (at least to about 5k, will worry about the rest next week.)

 

Other observations:

1) Linkage is CRITICAL. MUST have linear arm throw.

2) THROTTLE STOP... let me tell you... if your throttle pedal stop is not correct and you jam the Weber arms into their stops while racing... you will get an incurable high idle and trash all your idle speed settings.

Make for darn sure you throttle pedal hits the stop before your Weber arms hit their stops and bend and f00k it all to hester.

3) My cylinder #2 wasn't firing, the other cylinders were all a "5" on my synchronizer and #2 was a "2.5". I took it back apart twice and reset the butterflys and everything else. Finally I went after the "Air Bypass Screw" and at about 3 turns out the cylinder started to run and makes a "5" on the synchronizer like the rest. Perhaps the shaft is bent? The shaft was sticking too, which I cured (mostly), but still maybe an incurable problem due to worn carbs.

 

Triples are a hoot to drive. They talk to you very clearly and have a wonderful sound and feel. Sometimes it seems like max power is not gained at full throttle, but at partial throttle until the engine is ready..

At certain RPMs you can go to full throttle and get an "rrrrrroar"

or back off to about 80% throttle and get an "rRRROAR" that will crescendo to a full blown WAIL at WOT screaming down the interstate. You have to feel for the sweet spot a bit and it is very rewarding.

 

Fuel consumption: I have gone through 2 tanks of fuel and barely driven the car 50 miles. I hammer it quite a bit. They go through a LOT of propellent at WOT. Perhaps I need to work on the mixture more. But I don't think Triples are for you if you have a problem with fuel consumption.

 

Timing: This motor runs at about 30BTDC advance at idle and 50BTDC at 3000rpm. I have verified #1 TDC corresponds with the timing mark. It runs and pulls good and doesn't ping. Damper bad? Dizzy slipped a tooth? I have no idea, but I know it runs good with timing that seems too much to be true, so it probably isn't true. I've checked with my timing light and a "Snap-On" timing light and got the same number. This is the next project.

 

Nite.

 

TJ

[SuperDan]

30BTDC advance at idle and 50BTDC at 3000rpm.

[duragg]

I've been using Pierce Manifolds for all my Weber jets and tech help lately:

http://www.piercemanifolds.com/

 

I spoke with them for about 30 minutes today, described my problem and he recommended some jets to try.

 

Very easy to deal with.

 

TJ

[cygnusx1]

I had dual 40DCOE's on my Alfa back in the day. I had picked up two carbs and manifold in a junkyard in Milan, Italy for $60. I LOVE Webers. They are totally tuneable and rewarding. The sound is mechanical music. I remember all about the progression ports, emulsion tubes, main jets, pump jets.....what a trip those were. Now I get to go help Buzz tune his tripple Weber Z. I do it for the sound!

[duragg]

Weber Idle Circuit is TRICKY~!

 

MAINS

I increased my Main jet from 115 to 120 and Air Corrector from 200 to 170. This makes it much more rich.

My Arizona Emissions numbers tumbled!

Loaded CO was 1 percent, increased to 1.8 percent (3.75 is limit)

Loaded HC was 600 (fail) , went to 320(pass) (limit 500).

Cool..., richer jet equals better emissions?

 

So I took my idle jet from 45F9 to 50F9 and then to 55F9.

I did this because my idle screws were like 3 turns out.

But each richer idle jet made a bigger bog on throttle tip-in.

With the 55F9s I got wiplash with each cruise throttle movement. Unacceptable

 

So I went back to my 45F9s and the throttle response is EXCELLENT.

But (crap)./.. the emissions went haywire.

50F9s got me 1 percent CO and 600HC

45F9s got me 8 percent CO and 1100HC (Progession ports prematurely exposed???)

I retarded the timing with the 45F9s and got 8 percent CO and 490 HC

Limit is 5 percent CO and 400 HC.

 

I'm begining to think the IDLE CIRCUIT IS CRITICAL...

Its like you HAVE to set the butterfly valves JUST short of the Progession ports... then NEVER touch them and find an idle jet that will work.

 

Too much idle jet and the Progeression ports are too far away and cause a lean miss.

Too lean idle jet and response is good but fuel flow is hideous.

 

Am I going crazy?

I am going crazy!

[duragg]

I suspect my #2 (Middle) Weber 40 DCOE isn't flowing right at idle, despite a rebuild and jet replacement.

 

What is the function of the thing called the "Exhaust Bleed" and can it impact idle running if messed up?

[Zmanco]

I suspect my #2 (Middle) Weber 40 DCOE isn't flowing right at idle, despite a rebuild and jet replacement.

Why do you suspect it? What are the symptoms?

 

What is the function of the thing called the "Exhaust Bleed" and can it impact idle running if messed up?

This jet bleeds some of the fuel from the accelerator pump back into the resevoir. It should not have any effect on idle.

[duragg]

Ok what happens is that Cylinder #4 (Fed from carb #2) doesn't make much power at idle, and sometimes it just misses altogether. You can tell by removing one spark plug at a time. THey all cause a change in the engine except #4, or wherever the rear barrel of that carb happens to be.

 

I moved the carb to Position #3 and the problem follows that rear barrell of that carb.

 

Adjusted the valves, checked compression cleaned the plugs etc.

The plugs are Bosch Crapinum... prolly need NGKs.

 

But just cant figure why that one barrell does so poorly at idle.

Carbs are rebuilt and I've tried lots of jets.

Pulls strong and tests clean at emission on the Mains.

But the idle circuit goes haywire after it sits at idle for a few seconds.

 

I think I will pull that carb apart again and check for debris or something weird. Hopefully I'd find a little piece of rubber or something in there.

 

Thanks.

[Zmanco]

After idling for a few minutes, what is the color of the spark plug on cylinder #4? Is it black, or wet?

 

You might try moving the idle jet from #4 to another cylinder to see if the problem follows it.

 

Make sure to pull the jets out of the holders when you're checking for debris. I found a very small piece of paper towel in one after I rebuilt mine, and I thought I had been very careful about keeping everything clean during the rebuild.

 

If you take the carb off again, I'd also check to make sure that the throttle plate for #4 is aligned properly. If it's too far off, I suspect you'll have too much air flow in that cylinder and be so lean that turning the mixture screw will make very little difference. Pulling the plug wire wouldn't make a difference either.

[duragg]

DCOE 40-151 carbs.

45F9 idle jets, car has a "lean pop" in cruise.

Throttle response is perfect.

 

Switch to 50F9s and Cruise "Lean pop" goes away.

But car hesitates on smooth throttle tip-in.

I tried 55F9s and the hesitation is way worse.

 

Back to 45F9s and the cruise lean-pop is back.

But the hesitation goes away.

 

Questions:

1) Should I try a different "F" number?

2) Does the "Air Bypass Screw" have any impact on this?

I was told the Air Bypass Screw is only for balancing one barrel to another. But nobody seems to know too much about these screws.

[Dtsnlvrs]

Well I just rejetted my Webers for the altitude here and this is what I am running.

40DCOE18

33mm chokes

4.5 Aux Vent

50 pump bleed

45 accel pump jet

55f8 idle

135 mains

155 air corr

 

The engine pulls like a raped ape past 2.5k, but is a little sluggish below that and will flat fall on its face if I nail the throttle. Part of it is the cam, and part is I need a smaller pump bleed. I could also try a 60f8 idle (tried a 55f9 and it is way to rich at cruise) and adjust with the idle screws. I am also going to ensure my throttle plates are set properly. I think once I get the differential ratio right for the tranny and engine combo...the carbs will come in nicely. Oh and I am running about 4psi by using a holly red pump fed thru the stock SU fuel rail, keeping the return line intact (no vapor lock here)

[duragg]

I've had a continual idle problem with my Triple Weber 240.

 

When I got the car I drained the gas tank and replaced the filters and rebuilt the carbs. But on a hunch I pulled them off again and the floats are full of water, or beer or pee or ...?

 

QUESTION:: Has anyone ever installed a float bowl drain system?

 

Those square covers on the bottom could be tapped and threaded and a simple drain and valve installed for occasional removal of WHATEVER might be settled into the bottom of the bowls. LOTS easier that removing, cleaning replacing.