Alright, so I'm hoping this thread doesn't just fall into the abyss, and Weber owners can contribute their insights.

Here's where I'm at:

I have a recently rebuilt 225 Slant. Runs really nice. I have HEI. I hooked up my 38, and it runs well, but mileage is iffy at best (16 highway).

According to:

http://www.racetep.com/webjettune.html

Webers "want more timing". This is confirmed here by this thread, which is pretty golden, albeit does shift in subject quite a lot:

http://slantsix.org/forum/viewtopic.php ... conversion

Problem 1 - I can't set mine to 10 BTDC. I get SCREAMING detonation.

Problem 2 WHENEVER I go into a situation where I need power under load (up a hill, heavier acceleration, etc) the carb AUTOMATICALLY leans out HARD.

I hooked up a Wideband O2 sensor, mainly because every visit to a Dyno shop is probably twice the price of one, and frankly ends up telling you less.

Here's my situation: I hit the gas about 1/4 and I get a pretty good low speed curve. Usually going between 13.5-14.5. Lightening the foot on the gas usually puts the O2 meter at anywhere from 10.7-12.5, which is obviously quite rich.

Under load or WOT, the O2 meter immediately goes anywhere from 15.7-17.5, then evening out at 16.0.

I changed a jet size (the carb comes with a 45 Idle, 145 Main and 170 Air Corrector), to a 150 Main hoping for some kind of change, and no go.

Only Good Symptom - At 70-80MPH, I can get a nice cruise at around 14.3 on the O2.

Basically, I'm in a situation where the engine WON'T accept the timing people are recommending. Also, I have a fuel curve that goes:

Off Accelerator -> RICH

Cruise -> PERFECT at Highway speeds, Rich, although only slightly (12.7-13.5) at low speeds.

Part Throttle under load -> ULTRA LEAN (15.8-16.5)

Full Throttle -> ULTRA LEAN, albeit a bit less (15.7-16.0)

Is this right? Should the Carb CONTINUE TO GET LEANER as the RPM goes higher/engine works harder??

I'm told by this helpful thread:

http://www.jeepforum.com/forum/f8/weber ... ndex6.html

That the Idle Jet is somewhat overrated, because typically the Mains come on even as low as 1800 RPM.

So here is my question: what should I do here? My thought is that the Main Jets seem to perform well (the CRUISE part), and the Air Corrector, which typically come on ONLY AT THROTTLE, may be too lean. I'm thinking about swapping down to a 155 or 150.

Unfortunately, the same Jeep Forum says the guy's "perfect fit" is a 145 Main, 165 Air Corrector jet. He claims this to be the absolute gold for his 258 Engine.

I can't (obviously) duplicate this, but you'd think they'd be close, right?

Uh, he also starts to get into drilling emulsion tubes, which is, uh, waaayyy beyond me. I'd prefer not to go there. These things are supposed to be insanely customizable without drilling!

Any thoughts? Anyone? Bueller?

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

Since I don't speak Weber, but you should be able to translate it if the weber has the appropriate equipment:

When the load goes up and the engine works harder the vacuum reading should be dropping (and even worse if leaned out)...at a certain point the power valve or circuit should open up and help put the carb back on track by dumping a large shot of extra gas into the air stream to enrich the lagging/sagging condition...on tuneable carbs like the holley you can determine where that point exists by driving with a vacc. gauge and installing the appropriate valve (or on other models a spring,etc...) so it tips in just before it gets bad and picks everything back up. Hopefully your weber has this option and a tune-able enrichment device...otherwise you have to upsize the main jetting to compensate for this, leaving other conditions too rich so that one can be just right.

If you get ping from "more timing" you may want to revisit the curve and see if you need to change the vacc. can to allow more mechanical or if the springs are too light or your governor just is too long and you are overshooting the prime range of timing desired...also note that during a lean out it may seem like it has too much timing and if both exist (lean and too much timing they will just make things worse...I would richen up the carb a bit then see if the timing can be changed a bit. (carbs don't anticipate like EFI systems so they need to be slightly rich to fill in the void that occurs when you go from flat road to hills or "passing mode"...just not overly rich).

Good Luck,

-D.Idiot

The Vacuum can is probably OEM, as are the springs. It is one of those NOS Electronic Distributors from Ray Orme.

Found it through this article:

http://www.slantsix.org/forum/viewtopic ... 1fafb2c209

Also, thanks for confirming the "Rich Bias" that carbs should have. I figured that RICH isn't great, but it also isn't dangerous like LEAN is. This is why I'm so alarmed!

Another quick question about timing: I'm told that the usual Carter Carbs don't actually provide vacuum to the vacuum can at idle, but it seems like the Webers do.

How would this affect things? Are there adjustments that should be made?

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

Don't those have adjustable power valves? Never played with one myself. Could be wrong.

CJ

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Part of Tyrde-Browne Racing

Which model Weber? 38 DGAS?

If it leans out as you open the throttle that's the main metering system. Main jet is primary and happens at lower speed with the air corrector coming in later. It appears that the idle circuit may be covering up the lean main circuit at low speeds and at cruise. DGAS types apparently have a secondary discharge called the overfeed enrichment circuit and a power valve circuit. The power valve circuit adds fuel to the emulsion tube wells richening the mixture. This should activate when vacuum drops below a certain threshold and eliminate the lean condition.

Fix the lean condition first! You will never be able to use full timing with a lean mixture as you have observed. I would go up several main jet sizes and then start taking fuel out of the idle circuit.

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Joshua

It's a Weber 38 DGES, same thing except electric choke.

Thanks for the tip! I'll move up to a 160 Main and see where it takes me.

I'll report back.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

I know nothing about the details of how to get where you want to go, but can tell you what the goal is. Your AF ratio gauge is a golden tool, and will tell you what you need to know. You can go lean at cruise and must go considerably richer at WOT. My slant really likes cruising at 15.5-16 AF. You are currently way, way too lean at WOT. It should be at 13.5 or so AF ratio. I would say your present WOT AF ratio is dangerously lean.

There must be some way to get a greater difference between cruise and WOT fueling. In the stock 2 bl carbs there were tapered metering rods that lifted out of the jets under load to enrich the mixture. Figure out how our present carb is supposed to do this, and tune for more difference. I think there is no point in fooling with timing until you get your fueling squared away. Timing is the icing on the cake, but it is too early. My car right now gets between 17 local and 27 highway (with OD). Yours should do better for sure.

There are probably other areas carb related that would benefit from tinkering: Timing of choke pull-off, temp of air inducted, temp of carb itself, (maybe a heat shield), type of air cleaner, etc.etc. You will make steady progress on this. When I first started tuning my EFI it was yielding 10-12 mpg. Little by little I made steady improvement. Don't give up on it, and don't stop looking for better. It is bound to be there.

Sam

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I'm running 170 mains on my 38 with timing 8°base, 30°mech, 46°total. Occationally pings slightly under part load. Plugs are reading good so I'm going to try a different power valve next. I'm getting around 13 mpg with my van while hauling stuff on mountain roads. If a different power valve gives me good results I will try experimenting smaller mains. I'm also running a MP dist with a curve that that is all-in at low revs which i need to address.
FWIW

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1985 Dodge B250 Van

Thanks, /'d Box!

This is huge to know. I'm a little shocked that 170 mains are still giving you a ping (the dude on the Jeep Forum says 160 is a pretty huge main), but this is definitely instructional.

Unfortunately, all I have is a 160 before it's back to the Carbs.net again.

Those guys literally have a license to print money, I swear!

Another note: It's funny that most of the Jeep Forum guys have a problem with "flatness" or "bog". I find this carb to be quite smooth. No probs on that side at all. It's the mega leanness that I have issues with.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

The pinging is due to running a race distributor in a brick, he needs to install a good heavy spring on one side and it will correct the problem and bring the advance in at a reasonable rate. This is a case where a timing issue can mask itself as a carb issue, which it is not, it just advances too fast for the small engine to lug the heavy vehicle.

-D.Idiot

I think it depends on where the pinging happens. 16:1 at WOT is too lean, and good timing would still ping. I know that for a fact from the tuning I have done with the EFI. You can see cause and effect instantly. It is much harder to make a change an assess its effects with carbs and distributors, so I understand the challenges and frustrations here.

Sam

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In this case the issue is very blatant, the MP distributors out of the box are all in at 1200rpm...so if it hasn't been modded and he's running the vacc. can and set it at 8BTDC static, it's at his 46+ degrees of timing off the pedal in 1st gear....no slant can take that without rattling (even the feather duster wasn't at 40 at that rpm...the distributor needs a spring change for use on the street- I've done this to about 5 of these for other people). I agree that if it's lean it will ping, but you can lean out a stoich/rich situation by adding more timing under that condition (i.e. if you light the fire earlier you burn all the available fuel sooner or in this case too soon), it's a very interrelated juggling act. Although it's not as immediate like watching the computer readout, it's really not that hard to dial in a carb and the dizzy with the O2 sensor and a vacuum gauge watching for the changes (and the vac. gauge is good at giving a nice estimate of throttle plate position at the tipoff point). Since carbs read a signal that is perceived from the end of the manifold, he might have to dial his AFR close like 13 instead of 13.5 and that's as best as it gets.

For /'d box, I'd get the springs changed first so you have a known curve that is better suited to your vehicle, then change the carb settings (as the timing curve change may cause your lean areas to richen up by lighting the fire a little later than the current curve and you may not need to jet up.

2 cents,

-D.idiot

Interesting. Just as I closed that post the question entered my mind to wonder if too much advance could mimic a lean condition. I opened this thread again with the intention of asking, and there was the answer as if by magic. This is a complex dance of inter-related parts.

What did Mopar do to make their combination work? I to tried to install a feather duster distributor in my car back when it was all stock except for electronic ignition. It developed a miss off idle, but I never figured out why. I just took it back out and replaced it with the one that had been in there.

What was Mother MOpes strategy for that combination?

I will be interested in seeing what his AF meter shows once the timing is fixed. I am aware that unburned fuel can show up on a narrow band gauge as lean if excessive. But was unaware that a wide band would do this.

Sam

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Just tried the 160s. No go. Very similar symptoms. Maybe a little richer both at cruise (13.3) as well as at wide open throttle (going as high as 16.8, eventually stabilizing in the mid 15s)

Ordered a pair of 180s and 190s. We'll see!

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

It sounds like the power valve isn't doing anything. It did end up richer with the larger main jet though so that's positive. At this point I would call Pierce Manifolds or some other shop that is highly experienced in these carburetors as your carb may have a defect that is obvious by these symptoms.

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Joshua