Engine will not idle - Weber Carb Tunning problem

M

mark_hagen

New member
First thread – long thread.

I apologize upfront for this long post. I have been pretty much self-sufficient this far into our 6-year father/son project, but now I am stuck. I have a 67 Mustang coupe with 200ci that I cannot get to idle, in order to set the idle mixture on the Weber Carb.

Here’s what I have;
200ci, .030 over, zero decked block
Weber 38 DGES carb
Classic Inlines modified 2V log, ported, polished, V8 valves
Clay Smith hydraulic cam (I think it is a 264/264 -112…..can’t find the paperwork on it)
HEI ignition
Weber fuel pressure regulator
AC mech fuel pump

Here is what is happening;
Per Weber’s instructions, the idle speed screw is tightened to just make contact with butterfly linkage (zero lash), and then turned ½ turn, maximum. This ensures that the carb is only running on the idle circuit and not getting any fuel from the enrichment holes or secondary circuit). The car is started and warmed up until the choke is fully open. When the accelerator pedal is released, the motor will only turn 400 to 500 rpm, and then quits. I cannot get the car to idle with only ½ turn of the idle speed screw. The car will not idle until the screw is at least 1 ½ to 2 turns; which is beyond the point where the butter fly plate movement has uncovered the enrichment holes (no longer idle circuit only). No matter how I try to tune it, I cannot get a proper idle with only ½ turn of the idle speed screw (which the Redline-Weber tech folks swear is the point where the motor should idle fine for idle mixture settings). Once the idle speed screw is turned 1 ½ to 2 turns, the engine runs fine around 750-800 rpm, even with the AC on. The idle vacuum is around 15”, which is a little lower than I expected. I was also expecting a little more overall power than we are getting, considering the mods we have done, but that is hard to quantify at his point.

Here is what I have done;
Checked for vacuum leaks; sprayed cleaner around base of carb and carb fittings to check for increase in idle rpm. All seals are good. Sealed off port leading to brake booster. Replaced already-new PCV valve with new-new PCV valve. Checked PVC hose and connections. I have pulled, cleaned and inspected the carburetor at least three times. Thinking that I was not getting enough fuel, I changed out the original .400mm idle jets for .050mm, then went to .055mm, then to .060mm, and still no change. I have tried various timing settings with some success in getting the minimum controllable idle speed a little higher, but the engine still quit as soon as I got close to ¾ to 1 turn of the idle speed screw.

My other thought was to check the cam timing, but I cannot find the paperwork from when I purchased the cam from Mike, 2 years ago. I’m afraid I will have to pull the can just to see what model it is, before I can do anything about the timing, unless there is a way to get at old invoices from Classic Inlines.

I am open to any suggestions that anyone may have, as I am at the end of my limited expertise.

Thank you in advance.

-Mark
 
Its not your fault. The info you have is wrong. And there might be a PCV issue with regard to the breather port some 38DGES carbs had.


You have to be so very, very carefull with aftermarket Webers which are sourced from some suppliers...they are very different. Each letter variation means something. Your carb isn't a staged mechanical secondary carb like:-

The 1st Weber 32/36 DFAV begat the 28 versions of the US made Holley Weber 52xx and 65xx series, or
the five versions of the Weber 32/36 DGAV. Each one looks the same, but are as different internallay as a bicycle is to a motorbike

Since a Weber 38DGES isn't a staged secondry carb like the 34 variations above , the set up instructions you are using are TOTALLY wrong. Your carb was designed as a 2-bbl simultanous opening carb, although there are some really bad slotted DGAV conversion kits which turn a 38 into a staged carb.

The good news is that from Novemer 1971 to late 1997, for 27 years, there were 27 and 29 mm venturi Weber 38 DGAS carbs in use for the 138 hp 2994 cc engine. It is a water operated choke version of the 38 DGES, just like yours. The details on it are here.

http://www.redlineweber.com/html/Tech/3 ... unning.htm

38DGAS Tuning


CARBURETOR SET UP AND LEAN BEST IDLE ADJUSTMENT

Base line Settings

Speed Screw 1/2 turn in

Mixture Screws 1 turn out

Final Settings Engine Running

Mix______

Speed_____

38-dgas_tunning_pict.gif



It is important to verify all linkage and levers are installed without binding and the linkage opens to full throttle and closes to the Idle Speed Screw. The number one and two reasons for tuning errors are improper linkage installations and over tightened linkage nut, causing a binding in linkage assembly.



CALIBRATIONS MAY VARY DUE TO REGIONAL FUELS AND STATE OF ENGINE TUNE AND PERFORMANCE. POOR RUNNING DOES NOT ALWAYS MEAN A BAD OR POORLY ADJUSTED CARBURETOR. AN ADVANTAGE OF THE WEBER CARBURETOR IS ITS EASE OF ADJUSTMENT AND TUNING.



SET UP ADJUSTMENTS

1. Start set up by confirming carb base line settings. Do not depend on the existing settings.

2. All settings are done with choke disengaged or warmed up so that the choke is fully opened and disengaged. This is done on automatic choke carburetors by first opening the choke butterfly by hand and inserting a wood block or wedge of some kind to hold open while the linkage is cycled (linkage operated through its full movement ) to clear the choke cam. (You will hear a metallic click as the choke cam is released. You can check the choke fast Idle screw under the choke assembly to confirm that it is not in contact with the choke fast idle cam.)

3. Set the Idle Speed Screw by backing out the Idle Speed Screw until it is not in contact with the throttle stop lever. Cycle or Snap the linkage again to be sure that the linkage comes to close without any assistance. (Checking for linkage bind) Now bring screw back into contact with the lever and continue to open or screwing in, no more than 1/2 turn in, maximum.

4. Set the mixture screws by turning each screw in until it lightly seats. DO NOT FORCE OR BIND AS THIS WILL CAUSE DAMAGE TO THE SCREW AND IT’S SEAT IN THE BODY OF CARBURETOR. Back out the screw 1 full turn.

TUNING:

1. BE SURE TO FOLLOW THE NEXT INSTRUCTIONS IN THE PROPER SEQUENCE, DEVIATION WILL CAUSE THE CARBURETOR TO NOT FUNCTION TO ITS IDEAL SPECIFICATIONS AND MAY NOT PROVIDE THE PERFORMANCE AND FUEL ECONOMY AS DESIGNED.

2. Start the engine, the engine will run very slowly more like a tractor. As long as the engine stays running idle speed is not important at this point.

3. The first thing, do not set “up” the idle speed, set the Idle mixture screw to lean best idle setting. First, turn in the mixture screw until the engine dies or runs worse, then back out the screw (recommend turning ¼ at a time). The engine should pick up speed and begin to smooth out. Back out 1/4 turn more, or until the screw does nothing or runs worse then turn back to the point where it ran its best.

4. Use your ear, not a scope or tuning instruments at this point. You want to tune the engine by sound. Adjust to best, fastest and smoothest running point.

5. Now that the mixture screw is at its best running location, you can adjust the Idle speed the screw. The idle speed screw will be sensitive and should only take ¼ turn to achieve the idle speed you like.

6. Check and set idle to your driving preference. Put the car in gear and apply slight load, (AC on) and set the Idle as you like it. Don’t set it too high, as this will cause causes excessive clutch and brake wear. The Idle only needs to be 650 to 800 RPM with light load or AC on.

7. Recheck timing and vacuum hook ups. Recheck mixture screw to lean best idle again. If all is still best and smoothest idle then confirm and note the final settings.

8. To confirm settings with the engine running. Start by screwing in the mixture screw and count the number of turns it takes to bottom out and note if the engine dies. If Idle Mixture screws are with in ½ turn of base line setting then all is well. Also check the speed screw and note how many total turns from initial contact. You may have opened (turned in) the speed screw. Your final setting should be under 3/4 turn in. Reset the screws (back in) to the best final settings (Per your notes) and go on a test drive. If the settings are other than described then you may want to recalibrate the Idle circuit (low speed circuit) to your engines needs. This is done by following the rule of thumb BELOW.

Simple Rules for low speed calibration

If the mixture screw is more than 11/2 turns out turns then the Idle jet is too lean (too small). When the mixture screw is ½ turn or less, then the Idle jet is too rich (too large). These assumptions are based on the fact that the speed screw setting is not opened more than 1/2 turn in. If the speed screw has to be opened1/2 or more turns then this is also an indication of a lean condition usually requiring greater change. At times it may appear to be showing signs of richness or flooding it is really a lean condition. Please understand the need to keep throttle plate as near to closed as possible so as not to prematurely expose the transition holes. This is what causes the visible rich condition, and confirms the need to increase the jet size. JET KITS are available if needed.

EXAMPLE With the idle speed screw set at no more than 1/2 turn in after contact with the stop lever; and the best idle occurring with the idle mixture screw set at 1 1/2 turns from lightly seating, indicates the need for a larger Idle jet. Achieving the best idle at less than 1/2 turn indicates the need for a smaller idle jet.

REDLINE
19688 Van Ness Ave Torrance, CA 90501
800-733-2277 Press Option 3

REDLINE is a division of WORLDPAC


The REDLINE Difference
http://www.REDLINEWEBER.com e-mail redline@redlineweber.com
Home
Click to expand...

Use the TVR 3000M, Taimar, and 3000S set-up details, which used the 38DGAS from 1977 to 1980 in US emissions form. Its basically a desmogged 138 hp Essex 60 degree V6 which used some Cologne 2800 V6 emissions bits. That engine is a United Kingdom 2994 cc 60 degree V6 carb, which was used on Granda GXL's and Capri II and III's, as well as South African Cortina XR6 's and Sierra XR6's. The South Africans used it till 1997 with a 38DGAS.


Weber has tuning data for it.

It has tamper proof idle setiings, so you can't benchmark the right settings without breaking the seals. The 38DGAS and 38 DGES are basically the same, but the float levels have to be right, the Emulsion tubes have to be F50's and the main jets 142/145 mains 185/185 air correctors, and the fuel supply on that carb had a bleed back system with a return line, so you have to duplicate it with a Holley fuel pressure regulator Follow these set up instructions. If using a Postive Crank Case Ventilation valve, it has to be dampened with two of the baffels found in later Ford rocker cover gaskets, and the PCV has to have a restriction spring on it so the float level doesn't suffer surging hydraulic engergy line influence.

South African Fords:
Cortina XR6/30S/granada 3.0:
45 idles
4.0 Aux venturis
55 accelerator pump jets
142 mains
185 airs

XLE cortina:
45 idles
4.0 Aux venturis
55 accelerator pump jets
145 mains
185 airs


Reliant Scimitar (running Ford Capri/ Granda 3.0 L v6 engine):

SE5/5a/SE6/6a 38DGAS 3A:
145 mains
45 idles
60 (Overdrive Dadenham 4 speed) or 70( C4 AND BW35 automatic) accelerator pump
185 airs correction jet
F50 emulsion tube

Ford capri 3.0:
Main Venturi 27
Aux. Vent. 4.0
Main Jet 145
Emulsion Tube F50
Air Correc. 185
Idle Jet 45
Pump Jet 70
Pump Bleed 30(1)
Needle Valve 250
Float Level * 40/52.5,<---- the details you should use if your floats are brass

For 38 DGAS 6C carb, 3.0 litre European spec Capri OEM jetting was......
27mm choke (main venturi, fixed)
4.0 aux. venturi
142 main jets
185 air correctors
F50 emulsion tubes
45 idle (slow running) jet
55 pump jet (no pump bleed info listed)
2.50 needle valve (gas inlet).


Float level varies with type. There are three kinds of float, and four kinds of settings.
 
HI, before you can do any adjustments the motor needs to idle.. so turn the idle screw to what ever the motor needs to run then do the timing adjustments and the air/fuel mixture screws .. I don't care what Weber says there is a lot of variables to make a motor idle. I've never seen a motor run with only a 1/2 turn on the idle screw. So turn it till it idles then make your adjustments..
good luck
tim
 
Long time since my original post...found two things. 1) brass tee fitting on intake manifold for brake booster and vacuum canister had a hairline crack on the underside. 2) PCV valve letting too much air to pass through at idle. The store bout PCV valves have spring tensions set for a stock motor. After researching how to select a PCV valve for a modified engine, I purchased and installed a Wagner Adjustable PCV valve (Not cheap). This valve has two circuits; an idle circuit and an off-idle circuit. Once installed, turning the idle adjustment screw made the engine idle smooth out. No more idle circuit problems.
 
xctasy":3mcirkha said:
Its not your fault. The info you have is wrong. And there might be a PCV issue with regard to the breather port some 38DGES carbs had.


....... If using a Postive Crank Case Ventilation valve, it has to be dampened with two of the baffels found in later Ford rocker cover gaskets, and the PCV has to have a restriction spring on it so the float level doesn't suffer surging hydraulic engergy line influence........


Float level varies with type. There are three kinds of float, and four kinds of settings.
Click to expand...


Thanks for the heads up Mark.

I'm sorry for the cost. That cost was unexpected, I'm sure. I am certain your new system addresses the problem, and everyone here will thank you for your feedback. Its absolutley certain that a Weber DG series with the stock PCV line hooked up may have idle and therefore fuel economy issues because of

the booster line check valve becoming a leak switch to irratic float level,
the PCV arrangment making float level erratic,
and possibly a combination of needle and seat and float level setting which may be more of an issue.

( a common fault I'm finding, in addition to the Webers absolute distain for not Weber approved low quality cheap parts that don't cope with ethanol or high aromatics, they hate dirt in fuel or grit in the air bleeds, all three common matters with the age of all components in our brake systesm, the fuel tanks in our cars, the substandard air cleaners we fit to replace the stock 1-bbl tin hats)



Its unacceptable for this carb to get the contnual bad rap due to the requirment to have the right kind of specific emissions era PCV parts fitted. The DGAS and DGES, while while not a brillant economy carb like the 32/36 and 5200/6500, they are great performance and economy carbs when set up right. Any European Ford or Renualt 30 with Vee sixes less than 3 liters that do 25 plus US mpg at 65 mph and sub 17 second quarter miles makes use of the pcv port, and restricts its flow from the engine. The carb isn't a wonderfull clean air carb either; Ford had a lot of difficulty making any DGAV/DGAS/DGEV carb as clean as any of its other US carbs. Even David Vizard commmented that the Weber and Holley Webers weren't as emmissions friendly as a well tuned 2300 series Holley 2-bbl. But it is always more economical, with a very good ability to make power with reasonable ecconmy. The 2-bbl 7448/9917 350 cfm , and 4412 500 cfm require internal work to get them to run well on a small six. The Weber requires external work on the emissions attachments, and some simple internal work. For my money, the carb you've got is the best choice.

The core problem is the PCV valve type. You've thankfully got it sorted. Like I said, another is the needle and seat which is very hard worked on any Weber carb. The PCV issue was discussed sometime back. Since every engine installation was custom built to the carb type, the other (cheaper ) way is to copy the whole PCV system.


They problem was solved in the Pinto, Lima I4's, and Cologne and Essex V6's with a two stage PCV system. The side of the block becomes the PCV suction source on the British and German made Pinto 2000 cc engines...when it got emissionised for Australian and 1972-1974 US market Cortinas and Pintos, they used the existing baffeled side reserviour on the block, a single stage flapper valve, and then a brass restrictor to the 32/36 or 5200 H/W or G160 Holley carb (similar to the DGES). On the Cologne V6, it used the conventional US 1973 on wards 3.3 T/B/X and 4.1 L and C PCV valves, but the suction zone was the rocker cover. When converted to US Emmissions, TVR used the Cologne V6 pcv valves.

Generally, the emmision era Ford 2.8 N code, 3.3 T/B/X and 4.1 L and C code rockers have all that good gear on them...Ford did a lot of work to stop oil getting into there carbs, but they used the log heads adaptor plate to tee into the area below the carb. The 1946C holley from 1981 on even had Fords patented Holley vacume purge system. And that was a little bit more compliacted again to your Wagner Adjustable PCV valve.

Weber used the DG series carbs in European Emmisions form, and in the French and Swedish PRV 2600 V6, Essex 2.5/3.0, they didn't use the same system. Those cars don't have problesm with fuel delivery or idle, they are sweat engines with reasonable power and reasonable economy.
 
"X" you are the man on Webers.
I see you have a DUI distributor. Part of you idle condition is the distributor curve.
Your DUI need to be recurved for you application. The 264 camshaft will kill your idle qualities.
You first need to get your distributor calibrated for your engine & then X can help you with your Weber.
PM me if you want to get your DUI re-curved. Bill
 
So how do you like that adjustable PCV valve? Is it worth the money? I've been looking at the thing and it's definitely intriguing...
 
All Six cylinder Fords came out with mild cam timing from 240 to 256 degrees, and the moment you go to 2-bbl carbs and you change the cam you need to


A. get rid of the stock pcv valve and

B. run the pipe from the carb to a baffled oil, seperator or catch tank.


C. If you can't duplicate the stock 2.0/2.3 Ford Holley Weber PCV set up, the 3rd solution is the Original Poster Mark's.


It's important to note three things.

1. Firstly, any PCV that vents to the carb also needs an air cleaner mounted line to the oil fillter cap. There needs to be a PCV line and a line to the oil filler cap, and a baffle under each.

Like this post 1978 rocker cover

IMG_8878pcvvalvebaffleAdjustablerockerdings.jpg



(NB//The red squares are where the adjustable rocker gear I used hits the standard Ford baffels. Anytime you use earlier 1971-1974 M code 250 2V or US 1960 to 1966 adjustable rocker gear, they always hit the later Fox and Maverick/Monarch/Granada rocker cover baffels. You need to stack cork rocker cover gaskets or make up a spacer plate to move the rocker cover up, and use some longer hold down bolts).


Without a line in an out, the PCV system won't work.
See this video. It's so common to do it wrong.

https://www.youtube.com/watch?v=XIw--72EKU0

2. Secondly. Without the baffels above, you have to revert to the way Ford from there first 2-bbl Holley Weber carbed 2 liter EAO Pinto engine in 1969 to the last of the carbed US 2.0/2.3 Lima OHC in the Ranger and Mustang Fox in the 80's. They did it using a baffled oil, seperator to stop the crank case ventilation pulses up setting the PCV port on carb instillations.


It is on every SOHC 2.0 to 2.3 liter carb engine from 1969 to 1988, and it sits here.

attachment.php


The installed intake manifold prevents it ever coming loose or falling out by itself.

There ws a last OEM Ford reference for it

The last OEM part number Ford gave F0ZZ6A785A or F0ZZ6A785AA. It has a 3/4" hole with tapered fit that just pushes into the hole in the block. It has a spring with a flapper valve inside to dampen the pulses from the crankcase blow by.


It works in conjuction with with a 3/8" internal diameter line to the rubber 1/8 inch by 1 inch grommet where the PCV valve sits.

6011482GR.jpg


that holds the common 3/8" hose PCV valve.


6011482.jpg



Here is how it looks on a 2.3 Lima block in the 1979 Fox Mustang/Fairmont/Zephyr engine bay


DSC_4779resize_zpsp7xqqh6r.jpg





It is called a crankcase oil/air separator or a positive crankcase ventilator oil separator.


It helps to relieve the positive pressure that is built up in the crankcase. It is a box having one hose runing in and one running out. One of the hoses that run from it is connected to the PCV valve


DSC_6347resize_zpsdtjqnbhv.jpg



Not having the PCV balanced and dampened before its hooked to the any of the Holley Weber or 32/36 and 38 Weber carbs often results in typical PCV jamed oen issues:-


- Oil consumption

- Bad idling

- Knocking engine (atomised oil in the inlet air causes a very low octane)

- Hard to start

- Bad to drive when driving off

- Vacuum leak like symptoms


The Third thing. We are often looking at turbo chargers, EFI or non standard , no longer 1-bbl engines that now have sixes that have totally different crankcase ventilation requirements.


When used, the system has to change to cope with blow by which is now directed into the carb.

The same EAO2.0 /Lima 2.0/2.3 catch can uses a two way system like the Capri RS Turbo, Mustang GT turbo, Mustang SVO and Merkur XR4Ti and Thunderbird Turbo SportsCoupe used from 1983 to 1988. Here is a common after market modification with an extra external catch can and blow by protection.

SVONewSetup14.jpg
 
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