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

[T-Bone028]

swa240z, I had a similar flat spot/bog when first getting into the throttle at low speeds or suddenly off idle. Mostly got rid of it by switching out the pump exhaust valve (its a screw at the bottom/inside the fuel reservoir for each carb) to a "closed" valve. My reasoning was that the accel pump needed to spit out more fuel for initial tip in. At $5/each, its a lot cheaper to test with and theres only 3 that you need to buy instead of 6.

 

Probably not the "correct" way to tune a DCOE, but it worked for me.

[Samurai7one]

I got mikunis and had similar problems with 3K bog. A bump up in pilot jet and main jet improved things a little. But adjusting the fuel level in the bowls (float adjustment) completely solved the problem. It's a free fix, so why not?

Measure the actual levels of fuel in the bowls, don't trust the "with the carb top removed, flip it over, measure the gap between it and the floats". That is just a starting point for float adjustment.

I don't know what the setting should be on the webers, but try to:

1) make sure the level is consistent across all three carbs

2) try raising the level about 2-3 mm and see what effect it has.

Hope that helps

[swa240z]

Chickenman - great read on the 510 site.  I'll try again to get the progression hole completely covered, but it seems like the last time I tried that, I struggled with idle RPMs.  As little as I know about getting these webers tuned, I know even less about tweaking the distributor to get advance exactly when you need it.

 

Regarding the vacuum advance, I find it interesting that there are those who think it is completely unnecessary to run vacuum advance with triples and those who think just the opposite.  Long ago, I had a mechanic who used to work on race z's outfitted with triples recommend that my intake be drilled out so that it would have a balance tube running between all 6 intake runners. I kind of remember him saying that it would improve overall performance and make the idle more smooth or something like that.  Anyway, I went with his recommendation and had the intake drilled out.  I have a bolt threaded in the end to close it off, but could easily thread in a port to hook up the vacuum advance if needed.  If vacuum advance was utilized, what specs would you recommend for static, centrifugal, vacuum and total timing for an L24? Just how much advance is too much?  Also, at what RPM would you have it max out?

 

T-Bone - In reading through this thread, I have noticed that others have had some success eliminating flat spots with a smaller or zero pump exhaust.  Like you, I don't know if that is the right way to correct the issue.  I'm not sure under what circumstances the fuel needs to flow back to the bowl via the pump exhausts.  To me, it seems like larger pump jets would be better than a zero pump exhaust but again, I don't really understand the reasoning behind the pump exhaust.

 

Samurai7one - I totally agree on the fuel levels.  I'm trying to find a tool to simplify the measurement but I'm having some trouble sourcing one.  Keith Franck developed a sight glass type that you insert into the well where the mains go, but I can't find it for sale anywhere on his webstore.  Also, another forum member recommended one from OER/SK Racing that ships from Japan.  Nothing seems to be available in the states.

 

I really appreciate all of the feedback so far.  It sounds like my next brass order needs to be:  130 mains and 55f9 or f8 idles and maybe some 0.0 exhaust valves.  What is the difference between the f8 and f9 and how will it impact my setup?  Thanks again!

 

Steve

Edited September 21, 2016 by swa240z

[Samurai7one]

On the mikuni phh carbs I can take the top cover off. Then I pull out one of the main fuel/ air jet assemblies. Then using a dial caliper, I use the rod that extends out of the end of the caliper's to measure down from the top of the jet block to the fuel. 23mm is what works for me.

 

Is this possible on the DCOEs?

Edited September 21, 2016 by Samurai7one

[Samurai7one]

Here like this:

https://youtu.be/meaGMoH4Pmw

[steve260z]

Chickenman - great read on the 510 site. I'll try again to get the progression hole completely covered, but it seems like the last time I tried that, I struggled with idle RPMs. As little as I know about getting these webers tuned, I know even less about tweaking the distributor to get advance exactly when you need it.

 

Regarding the vacuum advance, I find it interesting that there are those who think it is completely unnecessary to run vacuum advance with triples and those who think just the opposite. Long ago, I had a mechanic who used to work on race z's outfitted with triples recommend that my intake be drilled out so that it would have a balance tube running between all 6 intake runners. I kind of remember him saying that it would improve overall performance and make the idle more smooth or something like that. Anyway, I went with his recommendation and had the intake drilled out. I have a bolt threaded in the end to close it off, but could easily thread in a port to hook up the vacuum advance if needed. If vacuum advance was utilized, what specs would you recommend for static, centrifugal, vacuum and total timing for an L24? Just how much advance is too much? Also, at what RPM would you have it max out?

 

T-Bone - In reading through this thread, I have noticed that others have had some success eliminating flat spots with a smaller or zero pump exhaust. Like you, I don't know if that is the right way to correct the issue. I'm not sure under what circumstances the fuel needs to flow back to the bowl via the pump exhausts. To me, it seems like larger pump jets would be better than a zero pump exhaust but again, I don't really understand the reasoning behind the pump exhaust.

 

Samarui7one - I totally agree on the fuel levels. I'm trying to find a tool to simplify the measurement but I'm having some trouble sourcing one. Keith Franck developed a sight glass type that you insert into the well where the mains go, but I can't find it for sale anywhere on his webstore. Also, another forum member recommended one from OER/SK Racing that ships from Japan. Nothing seems to be available in the states.

 

I really appreciate all of the feedback so far. It sounds like my next brass order needs to be: 130 mains and 55f9 or f8 idles and maybe some 0.0 exhaust valves. What is the difference between the f8 and f9 and how will it impact my setup? Thanks again!

 

Steve

The float level is the most basic thing. Don't need any special tools. Yes, Keith and others have come up with cool novel ways of measuring the depth of a fluid in a hole. That's all you're doing. Do this, just cut a white strip of paper or card stock the width to dip into the hole. Make a mark 25mm from one end and look and see when the paper breaks the surface of the gas. That's it. You know how to do it.

Don't try to to bring in vacuum advance into getting the Webers running right. The solution is within your engine bay right now. Set the max advance at 34. Wherever that leaves your static, that's what it is.

Edited September 21, 2016 by steve260z

[Chickenman]

 

Don't try to to bring in vacuum advance into getting the Webers running right. The solution is within your engine bay right now. Set the max advance at 34. Wherever that leaves your static, that's what it is.

I'll have to respectfully disagree with that Steve. Please bear in mind that this method of Ignition tuning greatly affects modified engines with larger overlap cams. The bigger the overlap, the more timing that is required. A 280 degrees cam typically needs 25 degrees at idle.  a 290 cam as much as 30 degrees. For street drive-abilty.  I explained the reasons why ( Low mixture density and Camshaft EGR effect ).

 

How this affects Weber tuning is that the extra advance at idle only ( and that is the key part ) results in less of a throttle blade opening. And that puts the Throttle Blade to progression holes in the correct position.  If you can't get the Throttle blade position right then you can't tune your carbs properly.

 

You can't realistically just set your static timing at 25 or 30 degrees for numerous reasons. A couple of obvious ones are that you will kill your starter motor quickly and you will have too much advance at low RPM's and part throttle or large throttle openings ( Mixture density increases and you will get detonation ) . So vacuum pot tuning is a sensible way to get the engine timing to where it needs to be and to decrease the Throttle Blade opening at idle, so that you aren't uncovering the Progression or Transition holes.

 

I've used this method of Vacuum pot tuning tuning on many, many different carburated engines over the years. All with larger cams. The effects have always been positive. A more stable idle, a cleaner idle and a higher manifold vacuum generated. Those are all positive results and are solely a result of being able to get the Throttle Blade position correct. And that requires running an asymmetrical advance curve, which you cannot do with just a centrifugal advance by itself.  Just my .02c 

[swa240z]

On the mikuni phh carbs I can take the top cover off. Then I pull out one of the main fuel/ air jet assemblies. Then using a dial caliper, I use the rod that extends out of the end of the caliper's to measure down from the top of the jet block to the fuel. 23mm is what works for me.

 

Is this possible on the DCOEs?

 

I have a cheap digital caliper that might work.  I'll give it a try tonight.  I was under the impression that 25mm was the target fuel level?  Are there different levels for different e-tubes?

Edited September 21, 2016 by swa240z

[steve260z]

25mm is the general target for Webers

[swa240z]

I just noticed that Samurai7one is running Mikuni's so that explains why he was recommending 23mm vs. the Weber 25mm.

 

I ended up ordering some 130 mains and 55f9 idles.  I hope to have them by Saturday.  I'll recheck fuel levels and try to adjust the throttle plate relative to the first progression hole tonight.  It is amazing how much time and money these carbs can burn up LOL.

 

Thanks for the help so far!

[swa240z]

Ok, so I just finished adjusting the throttle plates so that the center of the plate is centered in the first progression hole, basically closing off the first hole.  Idle RPMs are now at 1800.  This is the reason why I originally backed it off so that about 25% of the hole (the part of the hole closest to the filters) remained uncovered.  At that setting, I could get idle RPMs at about 900.  I can't really control it at all with the idle mix screws.  I can bring the idle down to about 1500 at 1/4 turn out on the mix screws, but it idles terrible when I do that.  Is there another adjustment that I'm missing?  Other thoughts?

Edited September 21, 2016 by swa240z

[steve260z]

Which model DCOES do you have?

[swa240z]

40 type 2

[steve260z]

Other thoughts?  Yes. spray for vacuum leaks

[swa240z]

I have suspected a small leak somewhere but I can never find it using carb cleaner. I replaced the seals on the throttle shafts last weekend, so I know those are good.  I might try some starting fluid or something more flamable than carb cleaner to see if it does a better job finding small leaks.

[steve260z]

Had an interesting problem come up. Car would idle just fine. Once driving it would tend to want to stall at stop lights or when slowing down. Kinda hit or miss...Never really consistent but progressively got worse these last couple of months. Just like the car was running our of gas or the coil would be crapping out. Checked all connections with the crane ignition unit, plugs, wires, battery, messed with he idle jets, replaced fuel filter and many other things but could not get rid of the problem. Even ran the car without the gas cap..No progress. Think I found the issue. The carbs are dead headed and my old fuel return line is open. But, I unplugged the line at the gas tank end and it appears the problem is gone. I don't know if something got in the return line and prevented the tank from breathing or what but I've run the car for an hour and no dying.... Ran around in circles trying to find the actual issue and hopefully its solved. Just wanted to post for anyone having issues with dead headed triples.

[zredbaron]

Interesting... what type of fuel pump + regulator solution are you running? PSI? Sounds to me like the return line is serving as a patch to your fuel delivery symptoms.

 

I run a high-volume, low-pressure, centrifugal, electric fuel pump that outputs 3.5psi for all flow rates. No return line needed.

[steve260z]

I run the low pressure Carter. Need to double check but think its the P4070..4 to 6 psi. No regulator. What do you mean by patch?

[zredbaron]

Sorry about the delay!

 

Carbs can receive too much fuel pressure, in which case performance degrades. Installing a return line acts like a shunt, or a relief valve, in that it would relieve overpressure (to a degree; it isn't a pressure regulator) via providing a path of lesser resistance for fluid flow.

 

If memory serves, the Webers don't like much pressure... 3.5 to 4 psi. I don't have my book handy.

 

In my mind, pressure surges up to 6 psi would likely degrade performance, and a return line might alleviate that symptom.

Edited May 25, 2017 by zredbaron

[steve260z]

Thanks, that's one solution I'm looking at. Others being the fuel is getting too hot and causing vapor lock and or something is up with the pump its self.