I bust the thread in my carb jet

[Grifter]

Hi

First poster here in MK2 forum so wahay!

I was taking one of the jets out the side of my carb today for a little spring clean and on putting it back in I buggered the thread. It is a Weber carb out the 3.0 I have. Is this repairable or will I need a new carb?

Thanks

G

[mk2 cossie]

Is the whole thread knackered or just a part of it?
If its only a part of it, I'd try and run a tap down it and put some ptfe tape on the thread of the jet

[drdeath]

you need to get it really wrong to bust the threads...

Best clean it up with a plug tap - its flat bottomed so will go all the way down.
If its the jet itself, then you can get replacements from a WEBER dealer or you can carefully restore the thread with some needle files

[Grifter]

you need to get it really wrong to bust the threads...

Best clean it up with a plug tap - its flat bottomed so will go all the way down.
If its the jet itself, then you can get replacements from a WEBER dealer or you can carefully restore the thread with some needle files

I didn't fancy trying to rework this thread so sourced another carb from a 2.8

Something that has been apparent with any of the weber carbs on the car is when I start accelerating after about 3 seconds there is a hesitancy and it stutters, I then just come off the gas and back and and it seems to clear, it is always after about 3 seconds. Any idea what this might be as it's pretty annoying.

Other things I have noticed are when the car was fully warmed the other day I turned it off and heard what sounded like a vac sound from the left side of the engine as the engine stopped, sort of like the sound you get when you turn off an air compressor, when you hear the hiss hiss of air as it is stopping, but not as loud. A few weeks ago I did trace a blockage to the front of the carb plate because the little heater valve was not closing when cold air was put on, have went over the rest of the vac system and nothing seem out of place.

One thing that is also consistent with this carb and the previous weber is when I put the hand over the top of carb it seems to smoothen the idle out, and increase tickover speed very slightly, leading me to think there is an air leak somewhere, it is slightly lumpy compared to how I had it running when I first tried the 38dgas, and before I had problems with the idle jet screws. Timing is 9 degrees btdc on unleaded, valve clearances checked, plugs 4 point, new dizzy cap, coil, pump, tank, sender unit and also new manifold gasket, plus 38dgas with new manifold mounting gaskets. I don't know if something has popped a leak somewhere in between times me trying to tune it.

I cannot understand how the first time I fitted a weber 38dgas I had it ticking over great on about 1 and a half turns out mix screws and no hesitancy but now it takes about 3 or 4 turns out no matter what one I try. I tried the instructions for setting it up numerous times and never made a difference.
/
The carb is jetted for a 2.8, I don't know if this is the same jets as for the 3.0 Essex but I was speaking to a guy today at car show and he said the weber 38dgas needs jetted for a 3.0 if using in 2.8 cologne.

Finally, would having the carb set up with the fuel return on the carb blocked and the return on the sensor taking up the slack cause any problems. My thinking was it really shouldn't because if there is a back pressure on the fuel then the return on the fuel flow sensor will take it up instead of the carb having the direct return. I done this mainly to avoid cutting and chopping the hoses up and allowing me to keep the sensor for the trip computer. It never caused a problem first time so no reason why it should now.

[hamis]

I recommend you try another distributor.I had this problem when i had oldsmobile 88 years ago.I tried everything including new carb but nothing helped until i changed the distributor.

[mk2 cossie]

If you can, try and get the jets, needles and emulsion tubes in the weber as close as you can to the specs of the 3.0 setup.
Ran a 38dgas on my old 2.8 set like that and never had any problems with hesitation or stuttering.

And, I also had the fuel return on the carb blocked and used the original valve thingy that was there to start on the standard pipe work

[Grifter]

I recommend you try another distributor.I had this problem when i had oldsmobile 88 years ago.I tried everything including new carb but nothing helped until i changed the distributor.

Was it the slight lumpiness problem you had on the olds? Once the engine is up and running and warm it seems ok but there is these problems:

On start up from cold it seems to fire up and sit at high revs however once throttle is blipped and choke is off it sounds like it is running on 4 cylinders, 2 on each side so balanced but still you hear the spitting from exhaust, not a smooth tune all being said. Revs go to about 650 after choke then as it warms it seems to start clearing itself and sit at 850

Also at cold if I jab the throttle down a good bit it stutters and pops then will clear, in saying that the problem is only ten percent of what it used to be and usually it will clear and build revs, after a few mins running it is usually clear. also doesn't cut out when revs drop, which was s a big problem I had before.

When starting to pull away it goes fine then you can feel a slight hesitancy after about 5 seconds, sometimes it is worse than other times, sometimes not there at all. Cant tell if it does this when cold because by the time I menouvre the motor out the garage it is warming up, but description of hesitancy when cold would probably cause the same symptoms in Drive when cold.

I reckon a good run would really help as it has never been further than my street and out of 1st/2nd gear for a long time, I hope to be looking at trying to get MOT later this week and a run will maybe see everything settling down.

I can't help but think something has changed since last year when I fitted the first 2.8 weber 38 because it ran so sweet that time, the engine would go right down to about 200rpm and was turning like a sewing machine, response was instant and very smooth, and nothing else has been done bar change manifold gasket, which was relatively new anyway, and slight adjustments like clean plugs, and set timing to about 9 instead of 12.

[Grifter]

If you can, try and get the jets, needles and emulsion tubes in the weber as close as you can to the specs of the 3.0 setup.
Ran a 38dgas on my old 2.8 set like that and never had any problems with hesitation or stuttering.

And, I also had the fuel return on the carb blocked and used the original valve thingy that was there to start on the standard pipe work

I will need to find out the jet sizes and post them here to see if they are for the 3.0 or some other setting the carb guy used for the 2.8.

I did speak to another carb guy a while back and he said he had the 38 dgas and he jetted them for 2.3, 2.8 and 3.0 so there must be different jets for the 2.8 and 3.0.

According to him for the 2.8 The idle jet size should be 50 & main jets 142.

[hamis]

Was it the slight lumpiness problem you had on the olds? Once the engine is up and running and warm it seems ok but there is these problems:

No,engine stumped for a second when i tried to accelerate fast,when continued normally.Also acceleration was not as good as normally.Maybe you should clean your carb with ultrasound cleaner.

[Grifter]

Was it the slight lumpiness problem you had on the olds? Once the engine is up and running and warm it seems ok but there is these problems:

No,engine stumped for a second when i tried to accelerate fast,when continued normally.Also acceleration was not as good as normally.Maybe you should clean your carb with ultrasound cleaner.

Carb is brand spankin......actually when I was moving it yesterday it seemed fine apart from this still very slight hesistancy, also not as bad as it was, and a slight jittering of the engine when cold but it soon clears. Still annoying though.

I reckon a good run might sort it out, can't do that till MOT done.

[Grifter]

I changed the leads today and it made no difference, also took it a good run the other day and gave it a bit of wellie, no problem with accelerating, no hesitancy etc.

There is still this misfire sound through the exhaust. Imagine holding at 2k revs and instead of just the purr it's like the plug is missing intermittently. Got the timing at 6 BTDC to accommodate unleaded, the mix screws are out about 5 turns, before I managed to have it at about 2 and it was fine.

Also checked the inside of the dizzy and the vac part is free moving and the 6 rotating contacts seem clean. Something I always notice is when I hold my hand over the top of the carb it seems to increase the revs and the sound is smoother, despite the carb being set up for a 2.8 as I was told.

When I run the idle mix screws out from sat one turn out the increase in revs is not smooth or easily traceable either, it's lumpy and once out to about 5 it seems bearable. /it seems to increase fast then after about 3 turns takes about 1 extra turn to increase it very slightly, so by this I do not know whether to keep going or stop - I chose to stop at 5 turns.

What else do you think can be the matter, is there anything else that can be checked, given the symptoms, hand over carb increasing revs, the intermittent miss from the ignition, and idle screws out way out etc. To me it all points to lean mixture and therefore idle mix screws need changed for bigger ones, but carb guy said it is set up for a 2.8.

I also put a colour tune on it and a vacuum guage, all seemed well apart from when I had the colourtune on and held revs up I could "see" this partial misfire - there was a constant stream of blue then when I felt the slight judder through the engine I could see the blue turn to black indicating the spark had stopped momentarily.

Everything else is basically brand new and has been checked - fuel filter, coil, dizzy, valve gaps, plugs, leads ,inlet manifold gasket.

[Grifter]

I got the MOT done and the readings according to the tester were in acceptable limits. The print off does not show CO2 I don't know why but the following reading are there:

CO = 1.98% limit is 4.5%
HC = 145ppm limit is 1200ppm

If you take a look at this video below this is similar to the problem I get although if I had a lean mixture what might these values of HC/CO be at? I wish they would have printed CO2 as this would have given me a better idea.

http://www.youtube.com/watch?v=z3RfCMqGTVE

I strongly suspect these values can be read as either a well running engine or a lean mixture? if so I might see if I can go back and get CO2 reading. From what I read I need to find out if o2 levels are excessive this will point to a lean mixture.

[hamis]

I think your best option is to find a garage that checks your timing advance is working properly and check carb for lean spots.

[Grifter]

I think your best option is to find a garage that checks your timing advance is working properly and check carb for lean spots.

I found out there is a rolling road near me so I might just pop by and see if they can put it on there.

[Grifter]

Had the car on rolling road - results are it is lean right through the rev range. Advice was to try bigger main jets as a starting point but I need to send the carb back as it is under warranty still and do not want to tamper with it.

[mk2 cossie]

the jets for the 38dgas are easily accessible from the top of the carb i seem to remember
Should be under the air filter housing, but i'm probably wrong

[Grifter]

the jets for the 38dgas are easily accessible from the top of the carb i seem to remember
Should be under the air filter housing, but i'm probably wrong

I know what you mean but I think they are air corrector jets, I got a good bit of info of the rolling road guy - seems to know his stuff about carbs, I do know the main jets are at the bottom of the float bowl and you need to remove the top to get them out.

I am perfectly capable of changing the jets and the guy I bought it from said it won't affect the warranty either so I asked him for a list of the jet sizes in the carb he supplied me with so I can bump them up a size. Hope to hell it works as I tried upping jets before from my duff 2.8 carb into a model set for the 2.3 carb but it done sweet FA.

[hamis]

Did you get it sorted?