gunman
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| posted on 28/2/12 at 08:38 PM |
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Any weber dcoe experts in the house?
I'm just about to strip and rebuild my twin 40's as they haven't been running right since I bought the car last year. Idle is very
poor and stalls after 10 secs unless you 'blip' the throttle to keep it running. I was also getting popping on over-run and they carbs
seemed to spit fuel out the trumpets as there's signs of fuel on the side of the car. It ran fantastic if you gave it the beans (which was most
of the time, hence it didn't bother me too much).
I checked the jets last year and got a bit of grit out of one of the main jets (on the worst offending cyl). Tonight I took the top covers off and
there's some dirt at the bottom of the float chambers. Internal and external fuel filters are fitted. I think a full service is needed.
Spec of car is a pinto which I was told is oversized to a 2.1 with a highlift cam of unknown make but a valve lift of 12.18mm. The main jets are 140
and the air corrector is 180. I haven't the rest of the carb specs to hand.
Any advice from anyone who has worked on these before? Am I likely to cause more damage than good attempting a rebuild myself?
cheers.
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perksy
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| posted on 28/2/12 at 09:18 PM |
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Sounds like they need servicing with a couple of service kits then setting up properly
Have had good service in the past for Weber service kits from Fastroadcars.co.uk
Dave andrews has some good advice on Weber carb spec and setting them up after servicing
http://www.s262612653.websitehome.co.uk/DVAndrews/webers.htm
Take your time and work methodically and you'll be fine
Did these 40's last year for a Westfield buddy
Before
During
After
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britishtrident
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| posted on 28/2/12 at 09:22 PM |
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Idle jets.
First take the idle jet and accelerator pump jets out and clean them.
The idle jets and pump jets are much smaller the main jets so will always clog up before the mains.
Also check the cold start enrichment device (ie the choke) piston valves are rising and falling freely, ie. closing completely. The little
piston valves in the cold start device can stick, ideally you should operate the cold start mechanism levers by hand every time you check the oil
and water.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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gunman
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| posted on 28/2/12 at 11:09 PM |
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Cheers Guys. One thing I'm not sure on is just how tight the carb to manifold bolts should be, there'sa good bit of play in mine. I know
there is meantto be some, just not sure how much. Last year I ran the engine and took a squeezy bottle of water to the joint to check for air leaks
but it seemed to be fine.
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gunman
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| posted on 29/2/12 at 09:17 PM |
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I took another look tonight to get the jet sizes, idle jets are 55 and pump jets are 40. I cant see any markings on the emulsion tubes though and
I'll need the carbs off before I can tell the choke sizes. I have a pair of service kits ordered so hopefully I'll be able to get stuck
in at the wekend.
I have been wondering for a while (which was made worse last night when it ws suggested on another forum) if the 40's are just too small for a
2.1 pinto? Do you reckon I'm wasting my time and should be looking to replace them with 45s?
It did go really well last year, all the running isues were at the bottom end of the rev range and even at that I could live with it.
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SCAR
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| posted on 1/3/12 at 07:44 AM |
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The pub expert will tell you you need 45's or even 50's. The reallity is 40's will be fine (other than for ultimate power with a
range of other mods and extreme revs) In fact you will stand a better chance of getting smooth botom end and good progression with the 40's. Of
course they need to be jetted correctly to suit your engine, I think 40's are fine up to about 150 bhp.
Be very careful with the petrol spitting back through the carbs, this is how fibreglass cars end up as soot
You also need to check compression in each cylinder and ignition timing/advance before you can finally set up the carbs.
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SCAR
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| posted on 1/3/12 at 07:49 AM |
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Just read your post again, if the engine has been like this since you got it and it runs clean elsewhere your rough bottom end problems could be due
to the cam, do you know what is fitted?
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gunman
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| posted on 1/3/12 at 09:13 AM |
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Thanks for the reply. I bought the car built last June and drove it over the summer inluding a weeks trip to my parents house which involved a 2hr
journey along motorway and country roads. The car wont idle for long but pops through the carbs (not all the time) on over-run from high revs. I
tested for leaks about the manifold but didn't find any and all but one jet was clear, when I cleaned it it ran better but still pops and doesnt
idle too well.
As for the cam, I had a post on here to try and ID it which was unsucessful, all I could do was put a DTI gauge on the cam and valve and got a lobe
lift of 7.92mm and a valve lift of 12.18mm. We couldn't identify the brand although it was suggested on another forum that it could be a comp
cam.
I lent my compression tester to a friend so am waiting to get that back to do a compression test, I'll need to buy borrow or steal a timing
light as well.
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gunman
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| posted on 3/3/12 at 06:37 PM |
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I started rebuilding the carbs today and have one done now. I got a synchronometer this morning in the post so I decided to test the carbs before
taking them off, they were out of balance by about 20%. One strange this is that the 2 chokes on the same carb were out of balance by about 30%. I
dont think this is s carb tuning issue. I did a compression test and got between 200 and 207psi between all 4 cyls so I dont think this is the
issue.
It was only when I had the carbs removed that I realised the plug which is plugging what I assume is the servo connection on the manifold is on the
intake which was way down. I'll check that this isn't leaking. I got it running reasonably well but seeing as I had service kits in the
drawer and I'd mucked about with the idle screws anyway, I thought I may as well strip them to be sure.
I was surprised to find the chokes stamped 30 as I reckon these are a tad small for a modified pinto, I expected to find 34's.
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Oddified
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| posted on 3/3/12 at 07:51 PM |
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A pair of 40's are fine on a modified pinto as stated above, unless your looking for the ultimate top end power and 180 - 200bhp then
you'd need 45's or 48's. The 30mm chokes are too small though, but if you change those for larger ones don't forget
you'll be into changing to larger jets at the same time.
The flaw discrepancy on the pair of chokes on one carb maybe down to a twisted spindle. Check that out, and fix it or it'll never idle
clean/smooth (it will probably have had a stutter the moment the rev's are raised from idle as well).
Ian
[Edited on 3/3/12 by Oddified]
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gunman
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| posted on 3/3/12 at 10:38 PM |
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What confused me a bit was I thought that a 30 would be 30mm diameter (internally) but when I measured it it got 34mm? They were stamed 30 tho.
My carbs seem to be over jetted for 30mm chokes anyway. 34mm chokes may be the best option. I'll see how I can get it running on these ones
first.
[Edited on 3/3/12 by gunman]
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SCAR
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| posted on 4/3/12 at 07:08 AM |
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The chokes can be bored oversize as an option to replacement. If you can do your own machining its a no cost mod.
I always assumed 30mm meant 30mm internal diameter. I think I have some std 30mm ones in the garage. I'll check
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gunman
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| posted on 4/3/12 at 10:32 PM |
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Thanks.
It gets stranger as I go along here. I rebuild both carbs and fitted them back on and tried starting it this morning. Got backfiring and flames out
the carbs, not a mission of starting. I had had the dissy cap off from when I did the compression test so I tried to make sure the cap was on right
and it was as it only goes on one way. Putting the engone back to TDC showed indeed that the leads were on the wrong way, No. 4 las lined up when No.
was ready to fire. I swapped them all round to the right order and it fired up. Only conclusion is that the last guy had the cap on wrong way
round.
Anyway, it's running better but still not 100%. I'll try to arrange a pro tune in the near future.
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