240Z triple webers

[sfmichael]

Hi guys,

I'm new to this forum and may be asking in the wrong area but I've got a friend with the 2.4 with webers (45DCOE) and I can't get this thing to stop fouling plugs, but only if he lets it idle too much. If it's driven and revved regularly, it's ok. He can't seem to learn to drive it that way (clear it out with intermittent throttle revs when idling very long) and it seems to me that I've got to have the biggest idle jets (60F8 I think) in it AND 2 1/2 turns out on screws or it has low speed/cruise misfire. Seems like too much but that's the only way it'll run decent at low speed. Always goes like hell at WFO but this seems like it should be able to be made more streetable.

Don't know what cam's in it, I know no history of the car and neither does he. Pretty sure cam isn't stock 'cause it won't idle much below a thousand rpm, but I'm bout at my wits end with this car. I'm pretty handy with the wrenches and I'm burned out on this f*cker, untold hours of messing/tuning with it.

I need the help of a Weber expert and if anyone here is, or knows one, I'd be deeply in your debt.

Thank You

[I'm BLUE]

:blink: ---> that sucks !

 

---> Use only NGK Brand Spark Plugs <--- Autolites are absolute :poop:

 

I am no webber expert , fuel pressure set at ? ( mechanical or electric fuel pump ). I used a Holley Fuel Pressure Regulator to set my 4bbl 390cfm Holley on my 240z L28 to 5-6psi per Holley's factory spec recommendations (electric fuel pump is capable or more than 12 psi easily :blink: ). I checked my compression , bought a vacuum gauge , and wen't to town on adjusting to the point where the intake manifold vacuum port off the carb ( full vaccuum at the base ) was set highest at 19-20lbs at 700-800 rpm idle.

 

My brothers Dual Weber 32/36 DGV-5a carbs will not operate correctly above 3psi , he has it between the factory recommended Weber specs of 2-3psi. His

 

Here is what I was told by my carb guy , and he said if anything goes wrong or out of whack , fix it before ever screwing with the carbs.

 

(1) Compression check ( even off at 10psi variance between cylinders can make it hard to tune )

(2) Ignition timing ( set it to where it is suppose to be , take off breaker plates - sand rust - lube them , check vacuum advance ports to make sure it is not rotten/stuck.)

(3) Check for intake manifold leaks ( spray carb clean on intake manifold mating surfaces , if you notice difference in engine idle ( speed up ) then you have a leak ---> fix it or it will never get in tune.

(4) Adjust Valves ---> Carefully , slowly , when engine is HOT ( operating temp ) not COLD.

(5) Do you have Electronic Ignition or Points ? ( this will cause a problem in itself , I have electronic now from pertronix and never looking back.)

(6) If you have a lumpier cam , you have less vacuum in many cases at idle , a mechanical advanced distributor might help remedy this issue ( very expensive though ) since you won't have to worry about manifold vacuum draw at idle anymore.

(7) I would put the jets back to where they were , and fix everything else first if you have any other problems.

(8) Buy tripple weber carb adjusting gauge ( the one you stick on the top and adjust vacuum ) , this will help save headache's hopefully ? ( I am not the kind of person that can "tune by ear" and have seen very very few people be able to pull this off successfully when they claim to do so :lol: )

 

This is just a few things off the top of my head , be back for more later. :D

[SHADY280]

45's are way to big for any 2.4. he should have 40's on it, that may help solve it. thats a great checklist above as well to start with. he may have to choke it down more as well. and yes ngk's are really the way to go. if the compression is higher than stock (comp check will tell you) you need a different heat range of plug as well. plus a good high power coil will help burn any unwanted extra fuel.

[I'm BLUE]

45's are way to big for any 2.4. he should have 40's on it, that may help solve it. thats a great checklist above as well to start with. he may have to choke it down more as well. and yes ngk's are really the way to go. if the compression is higher than stock (comp check will tell you) you need a different heat range of plug as well. plus a good high power coil will help burn any unwanted extra fuel.

 

^^^ +2 , 40DCOE are what my brother has for his L24 , and +10 on the highpower coil ( pertronix flamethrower is 25% supposively advertised gained spark 0-3,000rpm ---> bought this one when I needed a coil replaced , and it really felt like a difference ! best $35 spent :cool:

[240ADAM]

I would make sure you have a better than stock cam, your engine needs more air with that added fuel. You say its pretty lumpy at idle, but that could just act like that because its so rich. If its a stock cam, get a nice lumpy one and that should help alot. Also I disagree with only running NGK plugs, I had triple webs on my Z and the NGKs would somtimes foul. I switched to Bosch platnum 4's and I never had a fouling problem again and it made a noticable difference in power and a smoother running engine. Oh where do you live?

[hang_510]

it seems to me that I've got to have the biggest idle jets (60F8 I think) in it AND 2 1/2 turns out on screws or it has low speed/cruise misfire.

#1 timing

 

#2 where are the idle mix screws at?

all should be @ 1 turn out from lean +/- 1/4 turn.

took me awhile to get this set on my duals

 

#3 next size down mains?

 

read: http://www.teglerizer.com/dcoe/webertune.htm

when I needed a coil replaced , and it really felt like a difference !

psychological. it made a diferance becuse the old was bad

[I'm BLUE]

psychological. it made a diferance becuse the old was bad

 

nope , actually I didn't believe it either. The one took off was an "oil filled" unit that was purchased 6 months prior from Baxter's Auto Parts , so it was fairly new. I switched out and tested another old coil I had , it was good too as well as same performance.

 

Finally I switched to the Pertronix Flamethrower coil , and a pretty big difference off the bat I noticed :D ( only to 3,000 rpm's as they claim , and I don't drive above 3,000 rpm , the z just pulls along :P :lol: Above 3,000 rpm's , I can be honest I can't tell , but for city driving I clearly can.

 

Although I wouldn't purchase this coil until just about everything else was in good running order ;)

[sfmichael]

Hey, thanks you guys for all the knowledgeable replies. I have been away for a while traveling but now am home and my nemesis has been waiting for me (ugh!).

Haven't worked on her (the she devil) since last summer/fall so some details are fuzzy in my memory, but here goes some facts about the car:

 

Engine rebuilt by local GM dealer (I know!) Compression is decent, about 180psi and doesn't burn oil.

 

Timing has been played with but found it happiest at 12-14 @ idle and 30-34 total. No vacuum advance.

 

Did have manifold leak...R&R'd intake, milled it and replaced gasket with new and also replaced all carb base gaskets with o-ring style w/ phenolic spacers.

 

Adjusted valves several times.

 

Replaced points ignition with Pertronix breakerless and also their coil. New NGK wires and Echlin cap and rotor. No help. Also replaced spark plugs (lots of times!) and tried NGK and Autolite and tried hotter heat range with no noticeable difference.

 

Cam specs unknown. Engine pulls strong from low rpm through redline, but rear diff is geared super low (specs unknown).

 

Tuned carb idle speed/airflow with old Uni-Syn carb tool to sync throttle opening and adjusted A/F mixture to best idle/low cruise operation.

 

I live in Sioux Falls, SD (about 1200-1400' elev) and I'm burned out on working on this thing. Hard part is the owner is a friend and a great guy, so giving up isn't really an option. Dammit! :) My typing sucks and would love to talk to one (or more!) of you Weber guys on the phone. Please help :-)

Michael Murphy ph# 605-400-5469

 

Thank You!

[SHADY280]

get a wide band o2 sensor and read what its doing. kinda the only way really. still think the carbs are too big. you may be able to swap them with someone looking for 45's. what chokes are in the carbs. you may have to put 36mm in there to get everything tamed down if the owner doesnt want to swap them out. the engine will run fine with 45's but like you said its fouling plugs. its like sticking 2 850's on a stock small block, itll go like hang, but wont idle perfect.

[sfmichael]

Thanks Shady (and everyone else:),

My Weber experience is limited but have had a fair amount of carburetor experience in general and used to mess with Webers in the past. The first thing I thought when I saw 45DCOE on the top was "overkill". I could try swapping them for 40's if you're reasonably sure that would help. The chokes/venturis (whateve you call them) are pretty small if I remember right. Seemed like the smallest available, but don't remember. Isn't that kinda the same as putting on smaller carbs? I'm gonna work on it today and I'll grab my notes on the current jetting and choke sizes.

Not opposed to using/buying the O2 tester, but I know what it's doing, it's way too rich at idle but won't run right unless it's tuned that way.

Are you suggesting the INNOVATE(sp?) tester or some other brand you've had good luck with?

Thanks again.

[sfmichael]

I would make sure you have a better than stock cam, your engine needs more air with that added fuel. You say its pretty lumpy at idle, but that could just act like that because its so rich. If its a stock cam, get a nice lumpy one and that should help alot. Also I disagree with only running NGK plugs, I had triple webs on my Z and the NGKs would somtimes foul. I switched to Bosch platnum 4's and I never had a fouling problem again and it made a noticable difference in power and a smoother running engine. Oh where do you live?

 

Would be very interested in finding the part number for those Bosch plugs, please reply.

Thanks,

Michael

[SHADY280]

yeah innovative is good, if you temp wire it, you can swap it from car to car as well. there are so many different combos for jets, immulsion tubes, and air bleeds that all work differently together. ive heard of opening up the air bleed on the bottom of the float bowl as well. most people dont even know its there. if you make the idles smaller, will it idle still? maybe try putting down your setup and then we'll try to see if there is an odd part out. heres a hybridz link, they have lots of weber setups listed. maybe itll give some ideas. its a long read, but if it works, well worth it.

 

http://forums.hybridz.org/index.php/topic/28318-weber-jetsall-who-live-for-their-triples-please-read-this/

 

 

the first guys setup, sounds like yours

 

Tripple webber 45's on lynx manifold running:

135 mains

155 air correction

32mm chokes

f2 emm tubes

35 accerator pump jet

f955 idle jets

"sock filters"

[240ADAM]

I saw that you are not using vac advance. I know that some people say not to use it with triples, but my car had much more power with the vac hooked up. Just a little input.

[sfmichael]

Thanks Adam and Shady,

Adam there is no provision for ported vacuum on the Weber set-up, are you suggesting straight manifold vauum as a source for the advance?

 

Shady, that link you provided is awesome. I started reading it late at night and had to give up before I got all the way through, but there is a wealth of information there. Thanks so much.

 

I found my notes on the carbs from last year's tuning escapades but forgot to bring them with me here to the office, they're at the shop. I will put up a full list. But I saw I have 70F8or9 idle jets AND 2.5 turns out. Anything less and this thing spits, sputters, and pops back thru the carbs telling me it's lean. NO outside air leaks I can find. Weird.

 

And now it's developed an intermittent hesitation that I'm HOPING is just the carb synchronization. This car wears me down, always something.

[sfmichael]

I did check carb synch today and all was well.

I tried a new coil just for grins because this new stumble/hesitation almost feels like ignition. But I've swapped all the secondary ignition components with little to no improvement.

Accel pumps can't really go bad in these can they? I thought about switching to the zero flowback accel pump do-hickeys, but wondered why it would just recently develop this intermittent stumble? Ran pretty good last year, main issue was plug fouling at low rpm or actually idle. Now it hesitates somewhat frequently but nothing really has changed that I can tell. I figured someone had messed with the idle speed screws, but not the case, the carbs were really close. This car is so frustrating. Didn't check timing or valve lash yet, but no reason for those things to change suddenly either.

This car doesn't get many miles put on it, but the owner does drive it like he stole it. And he did mention he ran some race gas in it, CAM2 he said. Wouldn't think that would really hurt anything?

I'm lost...

[SHADY280]

id check those air bleeds. plus get a fuel pressure guage on it. the pump may have gotten better or worse ground (if electrical) and making the pressure not correct, flooding the carb

[SHRALP_GNAR]

"45's are way to big for any 2.4"

 

45's being too big for an l24 is a common misconception. You can fine tune them for any application. I'll agree that if you are going to invest in some new webers you won't benefit from 45's over 40's

I got a good deal on some 45's and they have been working great.

here's my jetting.

135 mains

180 airs

55f2 idles

f16 emulsions

34mm chokes

5 aux. venturis

Plugs always read clean with a only a hint of color. Pulls hard to around 6000 with no flat spots.

Are you making sure your throttle plates are aligned through the progression holes?