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West coast Weber guys--what jets are you running?
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smitty24
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PostPosted: Tue Jan 22, 2013 3:47 pm    Post subject: West coast Weber guys--what jets are you running? Reply with quote

Hey guys, I know this may vary. With dual Idf carbs, what jets are you all running? Since moving back to the NW, I can't get my engine to run right.

I have tried multiple combos with my engine, even 3 different distributors. Still have flat spots when you mash the throttle. Pumps are adjusted.

Currently has 50 idles, 125 mains, 190 airs, 28 vents. Engle 100, Weber 40s, 1679cc. 3.5psi fuel. Valves set, engine is tuned. Distributor is currently Pertronix 034, timed to 30* full. My thoughts are that the 125 is a hair on the large side, but it is hard to tell.


Thanks
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tattooed_pariah
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PostPosted: Tue Jan 22, 2013 3:55 pm    Post subject: Reply with quote

I've always used this:

http://www.cbperformance.com/SearchResults.asp?Cat=152
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flyboat
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PostPosted: Tue Jan 22, 2013 4:19 pm    Post subject: Reply with quote

I'm on the east coast. I have 135 mains, 50 idles and 200 air, 36 vents but I have 44's on a 2276. My heads are massive and I'm making right at 200 hp. So this info may not be applicable. It is a street car and is streetable with no issues. I tried 55 idles and it was running rich and I could not get it lean without going back to 50 idles. I wanted it rich thinking it would help the nitrous set up. Turns out, it hurt it. I plan on taking the car to a chassis dyno in mid Feb with multiple jets in hand.

If I were to change anything on your set up it would be the air jets. Try 200. Also, check the seats the needles sit on. If they are boogered, it will be tough to fine tune it. If you have a adjustment needle that makes a big change in 1/4 turn and not much after that. The seat or the needle is bad.
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75smith
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PostPosted: Tue Jan 22, 2013 5:05 pm    Post subject: Reply with quote

might try 1.40 main, 2.00 air, .55 idle

my guess is the flat spot is from a lean spot with small mains, and the 190 air is covering it up

have you used the aircooled.net jetting guide?
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webebuggin
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PostPosted: Tue Jan 22, 2013 5:25 pm    Post subject: Reply with quote

2110 with44 idf's 36 vents, 140 main,55idle 200airs,f11 e-tubes..
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pdub
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PostPosted: Tue Jan 22, 2013 5:28 pm    Post subject: Reply with quote

I'd try bigger idles just to see what happens. Go to 55s. If that cures it go down to 52 and see if those sork. Otherwise try moving your timing around a bit, try 32, if worse try 28.
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modok
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PostPosted: Tue Jan 22, 2013 6:26 pm    Post subject: Reply with quote

"Flat spots" is not something that means anything to me. First determine if it is lean or rich, and at what conditions, then we can decide what needs changing.

Play with the timing or jets and figure it out
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smitty24
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PostPosted: Tue Jan 22, 2013 6:32 pm    Post subject: Reply with quote

Thanks all, for the input...

I have chased my tail on this engine, for weeks.
-timing changes do nothing for the flat spot except make it worse.
-52 idles were running too rich, even after mixture adjustment. The 50s choke and pop a little bit.
-115 mains too small...ran rough. I have tried 125s as well as 120s. Neither make any difference. The 125s may actually be a little too large for this engine.

I can't believe CB recommends a 130 main for dual 40s. I ran 115 on my 1904 at 5000 feet. According to Aircooled's site, the 120 would be right for me at sea level. 130 seems downright too large.
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smitty24
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PostPosted: Tue Jan 22, 2013 6:47 pm    Post subject: Reply with quote

The engine has a faint hesitation off idle...but that is not the main issue. When you get it going at any speed and shift into a higher gear, it lags enough to make you and the passengers jolt forward. When you accelerate fast, it also hesitates. It gets a good shot of fuel when you blip the throttle. It does not do this in the garage, only when in motion and load is applied.

nothing I do fixes it. I have put 3 different distributors in. I have played with multiple timing settings on each setup. I have changed jetting over and over, played with the squirts multiple times, changed plugs, checked valves...nothing is working. Im approacing my whits end, here!
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modok
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PostPosted: Tue Jan 22, 2013 6:59 pm    Post subject: Reply with quote

ok, well done

I am familiar with a problem that manifests itself especially as a "flat spot' after each shift. This problem is poor atomization. you may have set yoruself up for such a condition with the small displacement, making for low airspeed somewhere in the intake tract that allows fuel to fall out of the stream.
if this is the case then you should have seen some help from more advance, even if it hurt overall power.
Atomization is a team effort between the carbs and the intake manifolds. The solution is therefore to improve the atomization. The carbs are only capable of what they are capable of. Thus: some improvement of the manifolds can help, such as roughing them up, or putting screens under the carbs, or switch to 36 or 40 DRLA, or alfa webers (which have superior transfer and acc pump atomization) and enjoy.
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pdub
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PostPosted: Wed Jan 23, 2013 5:55 pm    Post subject: Reply with quote

How do you know it's too rich? Wideband, plugs smell? You might think its too rich but the engine may disagree. Old cars usually smell rich unless you get a stock duration cam and add fuel injection and a modern ignition. I guess the main question is how did it run with the 55/52 idles? forget about the smell and AFR gauge for now...
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smitty24
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PostPosted: Thu Jan 24, 2013 8:01 pm    Post subject: Reply with quote

Thanks Glen. I think the next thing to try is something that we discussed a month or two back. (screens or Jetavators etc.) The only trick now is to build something that won't allow vac leaks at the manifold top.


Pdub, I know it was too rich by a few factors.
1. when trying to tune the idle mixes, (with 52 idles) the screws were hard to get to respond. Smaller idles fixed this.
2. larger idles also made the engine respond slower and have more lag.
3. smells are terrible even with correct tune...as in choking rich exhaust smell inside car and outside. Consuming far more fuel as well.
4. plugs were too dark and smelled.

Im going to go back to 120 mains, 200 airs, and the screen trick. If these don't do anything, stock carb might be going back in.
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udidwht
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PostPosted: Sat Jan 26, 2013 9:35 pm    Post subject: Reply with quote

Running Weber 40 IDF's Italian (Seattle, WA.)

28mm vents
50 idles
120 mains
180 air correctors
F11 tubes

Type-4 2056cc

I'd say you have an issue with that Pertronix dizzy. I'm running a German 009 re-curved slightly and have no stumble issue/s.
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PostPosted: Sun Jan 27, 2013 12:26 am    Post subject: Reply with quote

All tests should be done on the road under load. In the garage in neutral does nothing for testing and dialing in your carbs. Dont mix high altitude principles with trying to adjust or justify sea level settings. Your at sea level so the air jets you should be starting off with are 200s.

Quote:
The engine has a faint hesitation off idle...


What ever idle you had in at that time of testing, go one step bigger. When jetting your first step is to determine the air jet based on your elevation. Other factors of having your transition come in early is also based on the air jet selection as well. After that, you use the formula. Forget rich that, lean this- at this time. Your main goal is to get it close and then dial up or down. If i remember correctly your running 40x35? So 1.5 x 40- 60 idle the formula always makes it a tad big and I use it for breaking in. So step down to 55s. Or whatever your running be it 35.5 intake valves adjust accordingly, in this case a 55.

Quote:
When you get it going at any speed and shift into a higher gear, it lags enough to make you and the passengers jolt forward.

Id start with a 120 main.

Lots of folks claim not to be able to hear an af adjustment when closing down on the screw. This is very common. Its very subtle sometimes, so turn up your idle 1k and then retune.

Reading plugs and reaming jets are last for fine tuning. Right now the whole goal is to eliminate the off idle stumble and then cure the transition hole.
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smitty24
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PostPosted: Fri Feb 01, 2013 6:33 pm    Post subject: Reply with quote

Thanks J.

Just to set the record, I DO all this testing on the road, with engine warmed up. Looks like I will be buying some 55 idles tomorrow. Maybe my 52s were just labeled or drilled wrong from Weber?

Put the 50s, 120 mains, 200 airs in yesterday...still horrible. Absolutely gutless, runs rough, lags every time you push the pedal down. I must be overlooking something here. If the larger idles do nothing, I will be pulling the carbs again for further internal examination. Maybe there is a passageway that is not drilled correctly, or junk in a pump?
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75smith
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PostPosted: Fri Feb 01, 2013 9:46 pm    Post subject: Reply with quote

when was the last time they were cleaned? sit long between uses(no winter/rainy day driving?) driven in dusty conditions?

I would guess is something is clogged, a full clean will tell though especially if its been awhile since a clean, and multiple swaps between engines
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gprudenciop
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PostPosted: Fri Feb 01, 2013 10:07 pm    Post subject: Reply with quote

Your jetting sounds right! When i ran idfs i had to tweak the floats a little to get them to run right! I had the exact same jets you have in there now! In tualatin!
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