Jetting a Weber 38/38 for a 200

[xctasy]

Jetting for the Weber 34DGEC (also known as the Solex 34TEIE) and 38 DGAS and its variants is based around the
1. emulsion tube choice,
2. the parent engine Cubic Inch Displacement and Volumetric efficiency
3. the resulting horsepower level

Everything uses the F50 emulsion tube, so its an easy calibration. The normal US market 38 DGAS uses the Essex/Cologne V6 135 to 138 hp 27/27 mm main jets, and 142 to145 main jets with 185 air corrector and 45 idel jet forlittle engines, but a 50 or 55 will work better on a 250 engine. The 2.5 mm needle valve and that will give you got basic results.



The jetting for the Jeep 4.2 liter 258 will be closest for the 38 Weber on a 200 or 250 Ford. Other jetting info comes from
the 2664 cc 2.7 liter PRV 60 degree V6 Renault R30
the 1990 cc 2.0 and 2294 cc 2.3 liter Cologne 60 degree V6 at 92 to 108 bhp net, Ford of Europe 2.0 and 2.3 Taunus/Capri/Granada/Sierra
the 2793 cc 2.8 liter Cologne 60 degree V6 at 135 bhp net, Ford of Europe Granada Mk II/III
the 2994 cc 3.0 Essex 60 degree V6, 138 bhp net, Ford Capri 3000GXL, 3000 and 3.0S, Relient Scimitar GTE, TVR 3000 M

Others have modified F7 and F6 emulsion tubes to create an F-This emulsion tube, and then test and tune the air corr and main jets. So I'm cerain you'll get great results with the 38 DG series carb.

As for the too small 32/36 Weber with stock box emulsion tube jetting from Pierce, you can regig it if you use some 258 Jeep smarts.

From uptillnow on page 3 at http://www.jeepforum.com/forum/f8/weber ... ndex3.html

Now, with that said the 32/36 can be made to operate a 258 Jeep. The jetting that seems to work for all around performance is a .75mm Primary idle jet and a .60mm secondary idle jet. Ussually both main jets are 1.45mm and a primary air jet of 1.70mm and the secondary air jet at 1.60mm.
Then, the trick is to have the engine idle at zero vacuum at the "S" port or spark port and the idle speed screw absolutley no more than 1 1/2 turns in. Then the timing is set to 8-10 BTDC, some go more and some go less. The idea is to have an idle speed and no pre-ignition.

 

[kerb12]

So some interesting news, after all this struggling to get the engine to idle well with the 38, I decided to play with ignition timing. It was originally at 12 degrees (according to the shop that set the timing initially) so I started advancing to see what 14 would feel like... it started picking up and smoothing out, and vacuum started increasing, so I kept going. Eventually stopped at 25 degrees and I'm pulling a steady 15", it idles great, shifts between park idle and drive idle speeds without a hiccup, and my idle speed and mixture screws are moving closer to where Weber recommends them to be.

I'm kind of worried that it's so high, but I'm assuming the timing mark on my pulley must just be off or something. No pinging yet, but I haven't tried any steady high rpm pulls to see how it acts with the vacuum advance kicked in.

Anything else I should be worried about? Is it possible that my timing mark is correct but there's just something so wrong with my engine setup that I need crazy amounts of initial advance just to run??

 

[yoozeq]

Did you check this setup on the road. What is your total timing now, you shouldn't get over 36* ?

I also observe that more initial = more vacum = better idle .. but I think that is not a correct way to tune up car, but maybe I don't have right

Disconnect your PCV from carb, close that hole in carb. You should also observe better idle and vacum...

Falcon Fanatic told me that we shouldn't do that becouse of emission and positive impact for the crankcase. But to the point if your PCV is broken your idle will be also bad ...

 

[kerb12]

I haven't checked it on the road yet... actually the car hasn't been out since I started working on it, so I'm waiting to get a solid idle nailed down before I start taking it out. Didn't check total timing, to be honest I was worried if there was a way to cause damage by revving it too much when the initial was so high.

I agree it doesn't sound right that just adding initial is the best way to tune, but then again vacuum is supposed to be the measure of efficiency of an engine, so how could more be not good?

Plan is to play around with it more tomorrow... Maybe swap the stock coil back in and see if it makes a difference, and then swap spark plugs with a stock gap and check that too.

 

[xctasy]

I haven't checked it on the road yet... actually the car hasn't been out since I started working on it, so I'm waiting to get a solid idle nailed down before I start taking it out. Didn't check total timing, to be honest I was worried if there was a way to cause damage by revving it too much when the initial was so high.

I agree it doesn't sound right that just adding initial is the best way to tune, but then again vacuum is supposed to be the measure of efficiency of an engine, so how could more be not good?

Plan is to play around with it more tomorrow... Maybe swap the stock coil back in and see if it makes a difference, and then swap spark plugs with a stock gap and check that too.

Quick, run and hide :nono: :fume: :shockin: ....don't let FalconSedanDelivery or Wsaiii hear you say that...

Yes, tuning the engine with the best igntion settings will restore idle vacuum, but the initial and total timing is decreed by four other things that FoMoCo wasn't concerned with from 1960 to 1983. They were emissions, oxygenated gas, and loss of lead, and the fact that we are car modification fanatics, and we fiddle with the stock cam, carb, exhast, head and ignition and emissions combination. Thats why we get away with stuff that Ford in 1965 to 1983 wouldn't have dared do for fear of the Feds comming down on them like a ton of EPA Excrement.

The reason idle advance needs to be bumped up, and total advance woundback is to suit the changes made when you tune a 3.3 or 4.1 to suit a carb not designed for it. Engines like ours like lots of initial advance, although it hurts emissions. Emission regs since the 1965 US Clean Air Act till the Unleaded Federal Motor Vehicle Emmission regs in 1983 has governed iron headed I6 ignition tune. Since then, we have oxygenated gas and the loss of lead, which forces different tact with respect to tuning these days. And in many instances with a few exceptions (like in Collorado and Cali), the orginal emission regs don't govern yearly title.

With Weber 2-bbl on leaded 93 aki fuel and 9.35 to 1 compression, alloy head Aussie 3.3 and 4.1's run 9 degree before top dead centre at idle, and 36 degrees total. The more efficient the engine, the less total advance generally. Idle vacuum on a really effiecient engine will be poor, as the more optimized your cam, compression, carb and igntion, the more power you'll get, and that often hurts idle vac.

When you run a Weber and iron head, and raise the compression, an I6 engine just loves initial advance, and you can go to 16 to 22 degrees initial if you are running 9.5 to 12:1 compression. Cam timing changes that too, with 260 and 264 degree cams needing more idle timing, and idle vac can be hurt if the ignition isn't matched.

Old 1969 to 1970 302 Boss mustangs needed 16 degrees and 34 degrees total just to pass CA emissions, that was on over 10.7:1 compression and with the best super gas. Modern 4 valve per cylinder engines on 89 aki hate running extra advance, and will hole a piston with too much. Every engine combo is different, and its not true to say more efficient engines need more timing or get better tuned engines get better vac. For instance, one account is that on the 426 Hemi on 120 gasoline can run up to 57 degrees total advance in some applications and make 500 hp doing it...it just depends on the head, cam, carb, compression. Some engines always have awful vac readings, the Boss 302 and Boss 351C are like that, and often, the Classic Inlines headed 200 or 250 without proper ignition set up. Each makes standout power on a dyno, and

 

[kerb12]

Wow, thanks, some great info there!

Well after a little more messing around, I backed the timing off slightly and the engine sounded fine at high rpm's (I didn't have anyone to help though so I couldn't check the total timing and rev at the same time)... I took the car for a lap around the block for the first time since I started working on it, and it felt great! So I took it for a longer lap... then a longer one... and then out on the highway... next thing you know I had driven for 40 miles! Hell of a first ride. Engine felt solid, no stumbles, and it dropped to a steady idle perfectly when I stopped at lights. There's definitely some tweaks I need to make, but overall a really successful weekend. Thanks all.

Final jet sizes so far:
idles: 60
mains: 155
air correctors: 180

 

[yoozeq]

Nice to hear that your car is rolling My Weber and DUI should be on place next week It's a lot of distance from US to Poland I think I will start with your setup

 

[kerb12]

Nice, good luck! The car in your sig looks great, by the way. Looking back now, I would have just used a DUI from the beginning... I think I may have figured out the timing problem in my car, and it's that my Duraspark is wired wrong. Mainly I think the white wire is going to the run terminal on my solenoid, not the cranking terminal. So I think my ignition module might be retarding the timing while the car is running, instead of during starting like it's supposed to, which would explain why I have to turn my distributor so much... they're probably canceling each other out and going back to 12 degrees! I feel kind of dumb now.

I'm going to take it apart and rewire the whole thing, adding in a relay so I can pull full 12v from the battery instead of getting power from the resistor wire too. Should give me a better spark with the aftermarket coil.

Anyway, the easy DUI hookup seems like a good idea right about now...

 

[yoozeq]

Exactly, at the begining I will put DUI + relay for full 12V and I will check how does it feel. After that I will try to put on weber. I also have head fom 79 - bigger valves etc., but it needs some work like port on it carb, valves etc. Will do that on winter

Check your advance with a lamp. You will see if it work in good way.