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

[zredbaron]

if i could MOVE the problem to below 2000 rpm (or above 7000 for that matter!) then i wouldn't ever look back...

 

unfortunately i don't think it's quite so simple, but fuel level is obviously a very crucial part of the equation.

 

at least we are heading in what seems to be the right direction for once, matt.

[Dtsnlvrs]

Regarding needle valve, I've read this is (not only )

 

 

In another word, it makes me think our rich/lean conditions could come from the needle valve too big in my case, it does not close enough quickly enough the flow in the bowl and create the rich spot I experience.

I guess it is going to be an easy check worth a removal of the top cover of the carb

 

This is going the same way the guys on innovate forum talked about to solve the rich/lean mid rpm condition. By playing with the height of the fuel might solve the problem. Actually I believe it will move the problem somewhere else instead of fixing it.

 

 

After looking at your graph again...I would not mess with your mains sys at all. That is a good looking AFR graph for a carb'd engine. However, I would put a richer idle jet in, than turn your idle mixture scres in a bit...your progression is lean.

[Lazeum]

I just came back from a trip to the Z storage house (parents )

 

I've checked the needle valve, the accelerator pump jet as well as the fuel height.

- the accelerator pump jets are actually 40 (quite small compared to what I've read)

- The needle valve is 1.75mm

 

The fuel height is waaaay out of specs. The floats are 26g (brass). With measurement made with vertical cover I have:

- Fully open: 4.5mm instead of 8.5

- Close (floats pad flush to the needle valve with no pressure: 8mm

- All the way: 12mm instead of 14-15mm

 

btw, after 2 weeks without running the bowl was almost empty with no gas in it. Is it normal? (the bottom of the bowl seems to be dirty, I might check fuel filter)

 

So could we still say the needle valve are too big in my case and might not close soon enough creating the rich spot? I would say NO. Actually I'm leaning toward the usage of a smaller one if I'd have to change anything...

 

The fuel level is then 4-5mm too high. This would make the mixture even leaner if I correct the height to be in spec. I have checked only one carb, others might be different but I ran out of time...

I would believe I need to increase main jet size prior to play with the floats in order to keep the AFR in the good/safe range for my engine.

Since I have wideband, that might be the safest and most convenient way to proceed.

 

Regarding the progression circuit. I have 50f9. Idle mixture screws are 1.25 turn from fully close as Weber books advice with very reasonnable and smooth idle.

When I accelerate normally (off throttle to WOT is more than 0.5s at 3000rpm at least) the engine reacts fine. When I floor it super fast as I did for the AFR logs, you come up with the curve you could have seen.

In normal conditions, I don't experience the stumble I've done during measurements.

I will increase first the timing to be OK (from 10º to 18º-20º) and see how it goes. If problem still exists, I start with the accelerator pump jet but I might have to change idle jet with new timing.

 

There're still some work to do!

[zredbaron]

yes, this is normal for it to be empty. this is why with an electric fuel pump you wait a couple secs before engaging the starter, and with a mechanical pump it takes a couple turns from the starter before it fires up. you need to prime the fuel lines and carbs.

 

you check the level after driving it, shutting the engine off, then immediately checking the level. the dirtiness you see is likely very, very fine powder-like substance that has been caking on the bottom for years. i had that too, but by all means, check your fuel filter just in case!

 

with regard to the brass float levels, i'd compare your carb stamp to the table on the triumph site if you haven't already.

 

Up to 300cc per cylinder use a 1.50.

Up to 400cc per cylinder use a 1.75.

Up to 500cc per cylinder use a 2.00.

Up to 600cc per cylinder use a 2.25.

Up to 700cc per cylinder use a 2.50."

 

So using this chart...a L-24 would require the 1.75' date=' but a L-28 or L-30 and larger should be using the 2.00.[/quote']

 

according to russell's book, you should be using the 2.00 and i'm on the fence between 2.00 and 2.25. i'll likely try the 2.00. definitely don't want to over-do it.

[Daeron]

I seriously thank all of you guys for sharing this... I grew up around twin and triple weber/mikuni/solexes on my uncle's cars, and cannot tell you how many engines and setups I have seen pass before me... but only in the last 4-5 years have I gotten into auto tuning as a hobby for myself (kinda thought it was beyond me before that, figured I would be half-fast at best) and there simply haven't been carbs in front of me..

 

So you are filling in the technical details that simply appeared to be magic tricks in front of my eyes as a kid, is what I am saying. Now next time the roadsters fire up, I will know what I am doing

[Dtsnlvrs]

I just came back from a trip to the Z storage house (parents )

 

I've checked the needle valve, the accelerator pump jet as well as the fuel height.

- the accelerator pump jets are actually 40 (quite small compared to what I've read)

- The needle valve is 1.75mm

 

The fuel height is waaaay out of specs. The floats are 26g (brass). With measurement made with vertical cover I have:

- Fully open: 4.5mm instead of 8.5

- Close (floats pad flush to the needle valve with no pressure: 8mm

- All the way: 12mm instead of 14-15mm

 

btw, after 2 weeks without running the bowl was almost empty with no gas in it. Is it normal? (the bottom of the bowl seems to be dirty, I might check fuel filter)

 

So could we still say the needle valve are too big in my case and might not close soon enough creating the rich spot? I would say NO. Actually I'm leaning toward the usage of a smaller one if I'd have to change anything...

 

The fuel level is then 4-5mm too high. This would make the mixture even leaner if I correct the height to be in spec. I have checked only one carb, others might be different but I ran out of time...

I would believe I need to increase main jet size prior to play with the floats in order to keep the AFR in the good/safe range for my engine.

Since I have wideband, that might be the safest and most convenient way to proceed.

 

Regarding the progression circuit. I have 50f9. Idle mixture screws are 1.25 turn from fully close as Weber books advice with very reasonnable and smooth idle.

When I accelerate normally (off throttle to WOT is more than 0.5s at 3000rpm at least) the engine reacts fine. When I floor it super fast as I did for the AFR logs, you come up with the curve you could have seen.

In normal conditions, I don't experience the stumble I've done during measurements.

I will increase first the timing to be OK (from 10º to 18º-20º) and see how it goes. If problem still exists, I start with the accelerator pump jet but I might have to change idle jet with new timing.

 

There're still some work to do!

 

OK where to start. Set your timing at 15-18 deg initial (your cam aint as big as mine) using the starter motor only, and no vacuum advance (disable it permanently)

 

1: install a 2.00 needle valve, then reset your float settings as per Weber for brass floats.

 

2: increase the idle jet to a 55f9, and turn the mixture screws in to get best lean idle at about 900-1100 rpm.

 

3: Re-synch carbs then repeat step 2.

 

4: Make a new AFR log and report back

[Dtsnlvrs]

Reason I say to richen the progression is that at 3k you are on the mains already.

[Lazeum]

I placed an order for some main jets, accelerator pump jets and 2.00mm needle valve (with Fast Road Cars eBay shop you've mentionned earlier).

As soon as the weather allows me to drive my car I'll do some trials. It is cold (kind of 32-45ºF) but it doesn't snow much, there's no more salt now on roads

 

I've also received the advance curve kit from Mallory to play with timing.

For sure, I'll keep posting updates on the board.

[zredbaron]

i too have pump jets and needle valves on order. i've also purchased 3 pump bleed jets to tinker with the accell circuit a bit more. but between the needle valves and the floats, we just might get a decent curve...

 

here's hoping...

 

(thanks russell and other contributors, regardless)

[Dtsnlvrs]

I am still waiting on my needle valves...darn mail from Italy is slow.

[Lazeum]

I've got mine from UK yesterday

It's nice to have "daddy" working in London during the week

[wondersparrow]

Good day everyone,

 

This summer I picked up a 240z for track use. My plan is to get it all ready for next spring. Like Daeron, carbs are new to me; and Webers are not the easiest starting point

 

Anyhoo, the car was previously raced (and I would assume tuned). While taking apart the carbs for rebuild etc, I noticed that all of the chokes were 38's except for one. Its on cyl #2 (unless I have them backwards, its the second one from the front of the car). Its a 34. I know some people run into detonation and cooling issues on cyl #5, so maybe I do have them backwards.

 

Can anyone think of a logical reason for this? Well other than the prev owner just never noticed or something silly. I was going to order a new choke for it, but I don't want to cause issues if there is a method to this madness.

[Lazeum]

I don't think there is any logic behind it. You should change the choke. Especially 34 vs. 38. That's a big difference. All carbs should have the same jets/chokes/etc.

For your info, cyl #1 is the one in front of the car.

 

=====================================

 

For others webers addict, I've done some trials this past weekend. In France, we have ok weather and 65°F I'm also in vacations for 2 weeks. I'll have time after Xmas to play with the car

 

I've first found a way to draw my power curve out of the rpm recorded during my AFR logs. Numbers aren't realistic but the shape is even more. I wish I had 250whp and 400Nm of max torque...

Wrong timing, carbs not set up correctly, Torque calculations wrong, I don't know what is the reason yet.

 

 

Torque drop like crazy after 4000rpm, there's room for improvement. From the shape of the curve I'm also questionning the software. Torque should only be a derivative curve from rpm + aero resistance. Nothing crazy as long as you keep no interest for numbers.

 

Since I'm running on the lean side, I've decided to make the mixture richer prior to do any change on fuel bowl level or timing.

Knowing also I'm going from lean to ~12.5, I'm going to make the combustion faster, Timing will have to be ajusted accordingly. If I try first to get optimal timing, richening the mixture might lead to knock since I might have to remove some degree to get timing back to optimal. Since I don't know how much degree I'm talking about. I'll fix roughly AFR first.

 

Only change so far was the main jet, moving from 130 to 135. Car feels already better. I'll get some AFR logs with this setup prior to change anything else (one change at a time, always )

So more to come soon!

 

=> On a side note, since I share info with you all, I've learned a lot. I do start my car after a while easily now since I know that I need to fill first the carbs bowl, then spray some into the manifold prior to crank the engine to start. => Much less frustration than before

[Dtsnlvrs]

 

 

 

So is this log AFTRER switching to the larger needle valve? If so, the AFR looks much better. You should put 1size larger jet in and then "tune" out the rich spot after 4500rpm with a larger air corrector.

[Lazeum]

Actually no, it is the same setup.

I did not really pay attention when I've done the curve, I've got couple of logs last time I've posted results. It might be a different one than the one I've posted weeks ago.

 

The 2nd Curve looks better (richer at ~3000rpm), that's true.

 

I did not change anything yet regarding needle valve or fuel level.

A new air jet is also in my plan, I've got 165 to try vs. the current 180.

[Lazeum]

I had the opportunity to play with the car today

 

I've done many AFR logs:

- First with the 135 main I did not do last week

- Then with some 140 main I've switched today

 

Car feels best with 140. A lot of gizmos coming from the engine are gone. Not the kind of noise I was woring about but without them, car sounds definitely better.

 

I've overlaid AFR curves for your convenience. you can see the impact of main jet change ONLY on AFR. Pulls are made in 2nd gear @ WOT.

 

 

Test conditions:

130 Mains: 45ºF, rainy, only me in the car

135 Mains: 35ºF, sunny, only me in the car

140 Mains: 35°F, sunny, Me and my dad (+240lbs)

 

 

I did not start the log as early with the 140's as I've done it with other jets regarding rpm.

We can clearly see the difference between the 130 and the 135.

Differences between 135 & 140 are more difficult to spot. The higher rpm at the beginning of the log does not help.

 

Even if car is nice to drive, transition circuit has to be improved. I have to adapt my driving style (I do not floor it at low rpm); idle valve and pump jet are next on my list to do. Light accelerations (30/40% throttle) show lean conditions not shown on those curves.

 

I don't have 145 to try out. So that would be enough regarding main so far.

Air jet seem to be ok, I like the fact AFR goes rich at little at red line (should I??? )

 

 

I've also checked bowl fuel level. Since I've seen needle jet, I'm confused about how to check fuel level.

Should I measure fuel level with ball spring all the way in or just flush regarding the 8.5mm measurement?

So far it is at 8mm with floats flush to spring ball.

Let me know your thoughts

 

Next step will be timing & needle valve, maybe bowl fuel level.

I'll report back when I've got more to show Tomorrow is supposed to be a sunny day (but cold)

[Lazeum]

I've also checked bowl fuel level. Since I've seen needle jet, I'm confused about how to check fuel level.

Should I measure fuel level with ball spring all the way in or just flush regarding the 8.5mm measurement?

So far it is at 8mm with floats flush to spring ball.

Let me know your thoughts

 

I've found the answer to my question here (link posted in the past in this thread )

 

 

[i']The open and closed measurements should be taken with the top gasket in place. The closed position should be measured just as the floats close the valve and not with the entire weight of the floats upon the valve. This is done with the top plate tilted a little over vertical.[/i]

[akumazeto]

Ok,,, I'm pullling my hair out. My car wont start. So here is what I have

l28 tripple webs, 130 mail. 180 air f11 50 f9. Now before I had the bleed falve taken out it was running ok. I took out the blled valve fromt he bottom of the bowl cause its old. replaced it with a new one. Needle valves changed from 1.75 to a 2.0 PSI for fuel is 3 1/2. Now it wont start. The floats are set to 8 1/2 close and 15 open. cahnged the spark plugs cause it was wet and cahnged out the spark plug wires and still wont start. Before all this happened it work when I drove it int he garage.

Any advise from anyone? Could timing changed in that fracture when I took it out and drove it cold? What the hell. I'm about ready to burn this car if I dont get this thing running soon.

[Lazeum]

Timing could be a reason. My distributor once moved and make the car very unstable with explosion at the exhaust tip (HUGE bang!) so it could be. It is worth a try, rotate the dist by several degree clockwise and see what happen (as long as you stay at low rev it would be ok), you'll need to check timing with light afterwards if you want to avoid detonation.

 

also, are you sure you've got sparks?

 

Then, maybe a compression check could let you know if it could be the engine itself.

 

I'm nowhere an expert but this is what I would do.

[zredbaron]

well matt, if i could get my curves as "flat" as yours, i think i'd call it a day and be damn proud. your 135 graph looks like your best bet to me. did you not change your airs for your tests? you gotta change those to match your mains.... see what she likes.

 

i'm still deployed in the middle east, but i had the opportunity to use a computer and wanted to report back that i bumped up my needle valves, pump jets, and bumped down the pump bleed jets as well as re-adjusted idles, mains, and airs to suit. all this after fixing my float levels.

 

although the car did like the changes about as much as changing the mains by the minimum increment, the dead spot is unchanged. i am at a loss and at this point i am simply writing it up as incompatibility between carbs and a true race cam/block at a certain rpm range. if i run the car like a race car, i find no such hesitation (ie in the power band rpm range above 4000). i don't know what else to try...

 

-mark