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

[cygnusx1]

  Sounds great and looks really fast too!  Here is a test drive on my recently restored 72 with triples.  In this video, they were jetted as I bought them from an unknown condition.  28mm chokes, 225mains, 170 airs, and F11 tubes  on 40dcoe's.  I have since upped them to 32mm chokes with 150 mains and 190 airs.  The motor is a stock L28 with headers.

 

 

 

 

Edited July 6, 2010 by cygnusx1

[zredbaron]

...and i bet it runs a hell of a lot better!

 

beautifully detailed engine bay. everything looks brand new!

 

cool video, brings back memories...

[Mikez31ss]

I recently "rebuilt" my carbs. I haven't had a chance to sync or set the idle speed and mixture. I've been waiting on some hotter plugs that just arrived,

Before the rebuild they ran perfectly with no stumbles or hesitations. A little (more than a little lol) on the rich side. In case you're wondering...I rebuilt them because of leakage.

I can't say much about engine mods because I don't know anything about it except what I've seen and done myself. It runs great. It's an L24 w/ a bigger cam. Also 3-2-1 header and an adjustable cam gear. It did have an electric fuel pump but the pump was putting out 9psi so I converted to a mechanical pump w/ a ProProducts FPR set at 3psi. It ran exactly the same after the fuel pump change.

 

Carb Type and Model: DCOE40 18

Main Jet 130

Air Correctors 165

Idle Jets 45 F9

Float Needle and Seat 175

Main Venturi (Choke tube) 30

Aux Venturi 45

Emulsion Tube F11

Accelerator Pump Jet 45

 

http://67.18.219.83/image_hosting/web_pages/Mike88se/images/240/webers.htm

 

BTW if anyone can ID the intake manifold I'd appreciate it. It has no logo or markings.

 

 

[Mikez31ss]

BTW thanks for the ride cygnusx1...that was fun lol. And that is a beautiful engine bay. Great car.

[duragg]

I've been reading on some other forums that there are some modifications to the Progression Ports that some people do? I think they concluded that the 3 progression ports were not necessarily in the ideal location.

 

Do some people add a 4th Progression Port?

I think I also read about some modification to the emulsion tube.

 

The idea was to help with the tip-in stumble that some have if I recall.

 

My '73 240 / L24 / DCOE40 is nearly complete with rewire, sitting 2 years and need to rebuild the carbs again I suspect. It ran pretty good before so maybe I won't F* with it quite yet... Just pump some clean fuel through for now.

[codeman583]

I didn't want to muddy the wter with a new thread on this.

 

I have a bone stock N42 head/Block, and a MSA 6-2-1 header that will be getting the 2.5" from the header back. I will be moving to an elevation of about 2800-3000 feet, and want to get it ready for being in that area.

 

I recently acquired triple 40 DCOE - 18's, and here are the specs:

175 Air

130 Main

F15 Emu

55 Idle

50 Pump

30 chokes

 

my ideal goal is to get the car to work well between 1000 and 3500 foot elevations, and eventually get a nice cam in it. I also have all the components to perform the EDIS-6 Megajolt Ignition so spark will soon be covered. I want to get fuel relatively close before I put more irons in the fire.

 

I have the mixture screws out 1 turn from the "light stop" the throttle linkage is sitting against the carbs no screw out, and I'm running the MR. Gasket 4-7 PSI pump, and a Dial adjust regulator bringing the Fuel Pressure down to 3 PSI

 

my problem is the lowest I can get the damn thing to idle is 1500 RPMS, then when I blip the gas it goes to 2500 rpm and stays there. also the car doesn't rev out past 4000 RPM's without some serious popping and sputtering. ALSO, I have te Vacuum advance piped to the "T" fitting off te canon manifold where the brake booster comes out... should I leave that unplugged?

 

furthermore this is a 90% street car... and eeds to stay as such. very little track time...

 

I know someone on here knows.... SHARE THE LOVE!

Edited December 19, 2010 by codeman583

[Lazeum]

Based on my little experience, I would say your idle issue is a too big idle jet (you did not specifiy the 55fx number on yours BTW). I was running 45f9 with good results on my modified L28 and upgraded cam - MSA Stage 2 at the time (= less vaccum => bigger jets from stock were required)

I'm also running 40DCOE 18, so progression ports should not be your problem.

With the choke size you're running, idle should be super nice

You might also have some leaks somewhere; run a hose from your ear and check with the other end for noise around manifold or use carb cleaner method.

 

Regarding the rest of your setup, sputtering could be due to ignition also. I would check distributor & coil.

Your main jet & emulsion tube are not so far off from what everybody else is running on a setup like yours. It might not be ideal but I don't think it could create such big problem..

 

One tip would also be to check float level before you start any further investigations. I've made the mistake and I had to start back from scratch (+ other members will remind it to you if I don't ).

2nd tip would be to get a wideband sensor, it is cheap enough to do not avoid it (other solution to tune carbs would be dyno time, it will be more expensive than wideband), you'll get better results quicker (than nothing I mean) and you'll be able to adjust & to diag your carbs in case of problem (sputtering à 4000rpm..... cough cough!!) + you'll learn in the process

If you intend to change your cam, carbs would have to be adjusted again later on anyway.

 

+ regarding your advance setup, you should unplug the vaccum (+ signal is probably very erratic since you most likely got pulses instead of flat signal from the runners) and let the distributor with atm pressure. you then need to adjust everything. To adjust idle advance, I let the engine run at idle and I rotate slowly the distributor until I reach max RPM.

You'll have to check total advance and make sure you'll get something acceptable. With stock compression, I'm not sure you'll get detonation but your engine might overheat and produce bad torque response. in this case, you have to do a trade off between inital timing and total until you install the Megajolt system (which I'd love to get on my car ).

Edited December 19, 2010 by Lazeum

[codeman583]

.....regarding your advance setup, you should unplug the vaccum (+ signal is probably very erratic since you most likely got pulses instead of flat signal from the runners) and let the distributor with atm pressure. you then need to adjust everything. To adjust idle advance, I let the engine run at idle and I rotate slowly the distributor until I reach max RPM.

You'll have to check total advance and make sure you'll get something acceptable. With stock compression, I'm not sure you'll get detonation but your engine might overheat and produce bad torque response. in this case, you have to do a trade off between inital timing and total until you install the Megajolt system (which I'd love to get on my car )......

 

corrections to make today then:

1. unplug Vac Advance

2. check timing (My car did get hot yesterday whe I was messing with it... I chocked that up to low coolant levels yesterday)

3. by adjustig idle advance yo turn the distributor until you can free-rev the car to MAX RPM?

4. ALSO, I did backfire out the carb a couple times yesterday on one of thos 3k-4k revs is it possible thats a vc advance deal or state of the current tune?

 

last question. Should I order a 45F9 then to try to get this thing close? It will be some time before I get the CAM for this car so should I order a size lower on the idle jet? just want to get it right.

 

tricked ya... LAST question: will this setup perform "decent" still at 3000-3500 Ft? I am setting up and tuning at about 1000 feet.

[codeman583]

also quick note that the carbs were freshly tanked and rebuilt just prior to my getting them...

[Leon]

This sounds like either a vacuum leak or a linkage issue. Test for leaks as Matt mentioned.

 

To check the linkage, disconnect the throttle arms and see if that changes idle speed. If not, physically close the throttle at each carb and see if that changes idle speed. If idle drops down, use a flowmeter and get readings at each carb. Individually blip each carb and again check each carb with the flowmeter. If they are flowing much higher than they did before then something is not right. The offending carb(s) may need the throttle butterfly centered properly in the throttle bore, as you said they were recently rebuilt.

 

Once they idle properly with the linkage disconnected, reconnect and make sure there is no binding or sticking in the linkage. The carbs should flow the same whether the linkage is connected or not. This is critical to a proper triple setup.

[codeman583]

gonna mess with that as well tomorrow... to get the idle to 1500 I have to physically pull up on the throttle linkage. otherwise it is at 2000-2500 rpm still.

 

so maybe pull the carbs to check the butterflies or run the smaller idle jet and if that fixes it were good?

[Leon]

If you decide to center the butterflies, just loosen the screws so you can move the butterfly. You will damage the butterfly otherwise. The butterfly adjustment tip is passed down from my conversation with Mike Pierce of Pierce Manifolds.

[codeman583]

thats a good tip!

[codeman583]

update:

 

went to the 45F9 from what was a 55F8 Idle jet. I am over in Central Oregon now so my elevation of around 3000 ft. with my other settings should be good I am assuming.

 

idle improved with better return springs, and other changes. now it purrs nice and low... but I have a couple other things such as bad gas, which is being flushed tomorrow, and I tried to sync them up and I am reading 5 across all the cylinders except the last one against the firewall which is reading a 2 could this be because of water in the fuel or old gas? I have my fuel running through "T's" from the front to back and ending as the back carb so maybe if there werewater in the fuel it is pooling there?

 

and when I go to start it it acts like it is running on 1 carb for about 30 seconds of dancing with the pedal then the rest come in, it runs pretty decent for a little while maybe 5 minutes, or a mile drive then it starts sputtering, popping, and running like crap at anything other then idle.

 

I have my timing set at 15 deg with the advance unplugged now as well. runs decent, however the transition from about 2000-3500 or so RPM is rough ad sometimes requires a flick of the pedal and clutch work to make happen... think this is where the old gas comes in.

 

I am guessing on the RPM's too because I just lost all of my gauges except the speeding and voltmeter. so a whole new issue to play with.

 

I have a lot more time to work on it now though so I am hoping to get it all dialed in.

 

all help is greatly appreciated.

[Lazeum]

Are you using a mech fuel pump? I used to but the change to an elec one helped a lot when I was started the car. the bowl were just full whenever I wanted to start the car and it helped a lot.

 

I would help to know where you stand AFR wise with your setup at transition.

 

What about the idle adjustment? how many turn with each screw to get the best lean idle?

 

Have you also checked your plugs? After many trials, mine used to be fouled because of bad setup, you might want to clean them at first. If it does improve, I'll suggest you change them with new ones? what the heat range of your plugs too?

 

Do you have the chokes still on the carbs? Have you try to play with it when car starts acting weird? that would help you to see if the carbs are running too rich or too lean.

 

 

 

 

Your problem can also come from the ignition. Have you checked your coil and distributor?

 

 

[codeman583]

coil and distributor seem to be funtioning fine.

 

using an electric pump and a dial FPR set at 3.5 psi

 

also no on the chokes.

 

my plugs also look like a clean brownish tan..... mocha to white mocha in color.

 

is there a way to test the AFR other then a wideband?

 

man I am green when it comes to all this.

[zredbaron]

Too bad this thread can't be separated into both a triple carburetor theory thread and a triple carburetor tuning thread. (The forum is 21+ freaking pages long, haha! Hard to sift through that many pages for something you remember being in there.)

 

Anyways, the following is posted in a performance thread and the discussion also belongs in this thread as well.

 

 

 

 

 

Every biggish-cammed highish-hp carbed L6 build I've seen does that, it's due to reduced V.E. and multiple carburetion in that rpm range. I.e., air comes through venturi once, gets fuel, then some air gets pushed back through the venturi due to late intake valve closing and picks up more fuel, then gets drawn through again, picking up still more fuel, at the next cycle. With fuel injection you could improve the A/F ratio, but you'd still have a big torque dip there, as it simply doesn't breath well at that rpm. What works great at 6500+rpm doesn't necessarily work all that great at 3800rpm...

 

Topic of discussion later shifts to various sizes of header primaries in an all-out autocross motor application:

 

Reporting back on my findings: 1 5/8" header primaries are the consensus.

 

1 3/4" primaries are for road race motors -- for autox, drop the diameter 1/8" to gain some low[er] rpm torque at a slight cost of high rpm power. Encountered stern warnings that 1 1/2" primaries would severely restrict a ~300 hp (flywheel) motor's power output (my outgoing headers are rusty Monzas from 1999 - 1.5"?). JohnC was also able to set me up with a header merge collector, which evidently should also help mid-range torque a bit as well.

 

In a related note, after reviewing Dan's recent comments on the A/F mix ratio, I wonder if I might be able to improve my A/F curve with a proper exhaust. I'm not expecting a cure of course, but I can't help but suspect a measurable improvement to the A/F dyno plot might result. Better flow out means less dirty gases remaining behind and therefore increased combustion as well, or so I'm thinking anyways. Hoping to slightly flatten the rich and lean peaks that will likely still occur.

 

There will be one other improvement on the dyno plot (unfortunately for the AFR theory, but fortunately for performance). Remember the radical cam that was put in the motor in 2008? I've finally tracked down the springs the cam was profiled for (the outer springs only design, limited to 7700 rpm). Anyways, the proper pairing of springs to cams is of course crucial (probably even more so for aggressive cams), making the total of 2 dyno variables: exhaust AND springs. ]

 

 

So although I don't yet have any data per se, I thought I might revive some of the theorists and offer that the plots "are coming."

 

For what it's worth.

Edited January 29, 2011 by zredbaron

[Randall]

Ok just bought me a 280z and the webers were tuned for a stoker motor the guy bought them and put them on a stock l28 it runs pretty rich but mainly at idle...lots of backfiring during warm-up.

 

so i finally got a chance to look at what was in them and here are the results...

 

Chokes - 32

Main - 130

Emulsion - F11

Pump Jet? - 45

Air Jet - unknown, not sure where it is

Idle Jet - 50F6

 

Sometimes i can floor it and launch from idle with no problems and sometimes it will get choked up and stutter for a split second. Not sure if the guy had the throttle plates set correctly but when i get a chance ill set them.

[luke240z]

Hey fellas, I've just joined from Brisbane, Australia after finding this thread and the numerous posts of infomation, so thanks to everyone who has contributed so far.

My current setup is an L24 with a stage 2 cam, triple 45DCOE 152's, match ported E88 head with 6-2-1 headers into an 18inch resonator with a 2.25inch exhaust and flow through muffler. At 3500-6500rpm it had a good punch to it but anything below was rough. It really needed to be edged up slowly then you could cut loose after 3500rpm. So the setup then was:

 

160 Air

130 Main

F11 Emu

50F9 Idle

45 Pump

32 chokes

 

I thought that the idle could have needed a boost to overcome that initial lag spot.... however I was so WRONG! When I ordered and fitted a set of 55F2, I barely made it around the block. It coughed and popped like a hairy goat, a rough bloody ride to say the least. I went back to the 50F9 and started from square 1. I removed all the throttle linkages, backed off all the idle screws and gave them a quarter turn after they just engaged. Then soft seated all the idle mixture screws and gave them 2 turns out. I changed my air correctors to 180 as they were part of the order and also to see if I was running too rich before and if not these would have told me. So setting the idle, balancing the carbies and mixtures we were ready for a run. Well this idle adjustment certainly made a big difference down low. It now pulls from 2500rpm with no problems. I though it was the jets but seemed to be a mixture issue. I went with the 180 air as well as I kept reading the ball park "choke size x 4" then "+50 for air" to see if this was going to run ok... and it does. After a glorious afternoon doing highway runs and take offs I am happy, in fact very happy with the outcome. It's not perfect as you can always tinker with these thing until the sun comes up but thanks for the help so far guys, I really appreciate it. So my final settings were:

 

180 Air

130 Main

F11 Emu

50F9 Idle

45 Pump

32 chokes

 

Cheers

Luke

[240zip]

how much mechanical advance are you running?