jrock4224 Posted February 5, 2014 Report Share Posted February 5, 2014 trying to sort out some dco"M"s on a l20b. in a 521 any help ... diagrams know how or general hey dip shits look here .... type shit would help..carbs came from down under trying to make them work and tune them ......any body famiular ... they were take offs and never used ..... need choke cable ideas too ...... the single cable through both lever is no bueno and yes this post is silver bullet fueled so extra confusing..... i will check it when i wake up to piss and eat a sammie. Quote Link to comment
EricJB Posted February 5, 2014 Report Share Posted February 5, 2014 Don't sweat the fuel enrichment circuits. I have never once used, or needed them. Pics and detailed Q's please. Quote Link to comment
Guest Rick-rat Posted February 5, 2014 Report Share Posted February 5, 2014 You need to put them on upside down if they came from downunder :rofl: 5 Quote Link to comment
EricJB Posted February 5, 2014 Report Share Posted February 5, 2014 That makes it a real bitch to set the float levels. Quote Link to comment
jrock4224 Posted February 5, 2014 Author Report Share Posted February 5, 2014 lol yeah no head ache ...... basic info at the stock setting of one turn out is too fat but 4.5 turns out work better even though that makes no sense to the carbs Quote Link to comment
TENDRIL Posted February 5, 2014 Report Share Posted February 5, 2014 good luck man these carbs are a pain in the ass for me but, im at 6300 ft, no chokes.... http://community.ratsun.net/topic/54307-weber-carb-guys-dcoedcom-jets-and-misc-qs/ Quote Link to comment
jrock4224 Posted February 5, 2014 Author Report Share Posted February 5, 2014 ok so back to reality .... truck wont idle seems way rich at idle but runs good revving and at wot but it ..........wont idle at all the adjustment barely moves the idle ..... there's some binding in the linkage that is requiring them to come back off and be sorted....... that's being addressed today ..... whats the best sync tool for this ? im not getting adjustment on all idle circiuts.... im doing the forward most one on each carb first then the second but the adjustments are so disimilar to get it close ... jetting has been out twice of course i didnt right it down ..... we were making sure the passages and jets were clean .... at one point it was flooding the rear most cylinder to foul it out.... Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 this seems to be a issue with these carbs some info i found I've got a set of 40 DCOM's on my Alfa/FNM 2300 in a 102 Roadster. They run great with outstanding behavior andperformance in all modes except idle.They were originally delivered with an odd idle jet that I've never heard of. Something like 69F119. Car wouldn't idle at all. I changed these to 60F9, which I happened to have laying around and the car would idle, but seemed to be too rich, taking just a nanosecond to catch as it came off of idle. This was NOT the dreaded bog-spot so often experienced when putting Webers onto the original Solex manifold for this engine. I have an original FNM manifold which is intended for Webers or Solex ADDH carbs, not the PHH primary/secondary units on the original 102.With the 60F9's it ran great as soon as it had cleared its throat, which took less than a heartbeat. The idle seemed rich, but I could maintain a 1200 RPM idle. Anything lower and it would tend to die.Today I dropped in some 45F9 idle jets. Absolutely cured the need for "throat clearing", with immediate pick-up from idle and smooth transitions through all revs and throttle settings. However, the idle behavior has degraded from not-so-good, to weird.With various fiddling I can get it to idle at 1,200, but after about 15 - 25 seconds it will start to slow down and eventually die. I can prevent this by adjusting the idle stop screw up to about 1500 RPM, but this is clearly a bandaid, presumably using fuel from the first transition hole to keep it going.Adjusting the idle mixture screws doesn't seem to make much difference, regardless of throttle stop-screw adjustment. Turning them too lean will speed up the cut-off and opening them to what is probably too rich will slow down the cut-off.I'm going to order some 50 and 55 F 9 idle jets, but I've always been under the impression that these jets have far more to do with the transition than the actual idle. As the original idle jets wouldn't allow any idle at all, clearly they have some impact.Note that when I went to the 45F9's, I started getting a few sharp pops from the tailpipe upon deceleration. This was not evident with the earlier 60F9s. I wondered if this was not due to a too-rich setting on the idle mixture screws (which were at about 2 1/2 turns), but efforts to lean them aggravated the slow-down and die.Lastly...The DCOM's have 4 brass standpipes that stick up just inward from the transition holes. I have no experience with these, but was advised that in some applications connecting them with a balance tube can help the idle. I have tried this, but it seems to make no difference. Might they be intended to have a separate single-point air-bleed screw that inserts equal air to all 4 barrels during idle, allowing the throttle plates to be set more fully closed? Perhaps this approach is what calls for the original weird idle jet? Weber 40 DCOM 4/5 jets: 55/F21 idle jet - Emmisions type carbs 5 hole progression much smoother carbs in town and more economical 125 main 160-165 air correctors F64 tube 35 pump 32 chokes* 4.5Aux vents *30 more effective unless heavily tuned, use 120main or 123 for winter on 30mm choke, use 155 air corrector with 120main,160 with 123main and 165 with 125main Quote Link to comment
EricJB Posted February 6, 2014 Report Share Posted February 6, 2014 Ok, Fairly simple stuff. First make sure you have all the other specs set. Valves, timing. ect. Disconnect the linkage from one carb, and just let the arm swing. Make sure the still connected one isn't keeping the carb from parking on the idle speed screw. Start it up and get it to idle. start with the air/fuels in as far as you can to make it run. You also want the idle screws to be out as far as possible. if they are too far in, your air/ fuels will do nothing. Once it is running, you will need a unisyn of weber synchrometer. I prefer the synchometer. Adjust the idle speed screws till you have the idle at the desired speed and both carbs pulling the same amount of air through the synchrometer. The air/fuel screws are like a faucet. In is lean out is fat. It doesn't really matter where they end up, but if they end up way out that usually means the idle jets are small. Start at #1 slowly turn the air/ fuel in, until the idle just starts to fall off. Then back out till it comes back, Plus a quarter turn. Go to #2. repeat. So now it should just sit there all by itself and idle. Turn it off. loosen the locknuts on the disconnected arm, so you can spin it and the length changes. Bolt it on. Now look at both stops on the idle speed screw and BARELY open the throttle(repeatedly). Adjust the rod so the stops leave their set screw at the same time, the same amount. tighten the linkage locknuts, recheck and you are done. Quote Link to comment
jrock4224 Posted February 6, 2014 Author Report Share Posted February 6, 2014 there back off... the jetting is way off and the truck needs to be used and although they run and go down the highway there way to out of sync/tune ...so we are gonna re group do some more research and try and get them ready on the bench .....pics.. this is the way these carbs came, wondering if this is in need of a screw .... in a few tuning guides they say they should be blocked off....fingers cuz i cant p/s ms paint worth a shit ... same on both carbs only opposite....missing screw location currrently what is in the carbs .... what o nthis chart reference a l20 for a starting point ? drrrrr we took a break and threw the king pins in my truck before we swapped the su's back on....... so he can commute to work better..... also these carbs made the truck smoke blueish gray smoke worse then ever ..... like it didnt before, if at all and now it is like a old rotary pick up.... Quote Link to comment
jrock4224 Posted February 6, 2014 Author Report Share Posted February 6, 2014 oh and is it just me or are cannon manifolds kinda over priced pieces of shit .....the surface where your nut cinches down on the casting of the manifold .....should been faced, the casting is so rough/uneven it tweaks the studs all to shit when u torque it down ...... 1 Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 those are vacuum ports and only one should be open to run to the dizzy. Quote Link to comment
jrock4224 Posted February 6, 2014 Author Report Share Posted February 6, 2014 ok ...... i wish i had a break down of these carbs .... some how the directions went with the linkage cam to trash ville....hans made a cool piece to attach his cable to the linkage and it works good, the carbs just aren't tip top enough for him to commute 40 plus miles with...i called him a pussy ....lol Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 oh and is it just me or are cannon manifolds kinda over priced pieces of shit .....the surface where your nut cinches down on the casting of the manifold .....should been faced, the casting is so rough/uneven it tweaks the studs all to shit when u torque it down ...... i had to gring down all the flanges to mate with the exh. mani. and to flatten them out since they all had angles Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 these carbs were designed to be more "fuel efficient" thats why there are 6-7 progression holes in the tubes instead of 3-4 like dcoes they are supposed to help throttle response and driving so your able to drive at all speeds relatively smoothly no matter what position the throttle is at 1 Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 i love my carbs above 2k anything under that is pretty choppy also my car idles at 900-1000, i can bring it down to 650-700 but it way too lopey Quote Link to comment
jrock4224 Posted February 6, 2014 Author Report Share Posted February 6, 2014 i had to gring down all the flanges to mate with the exh. mani. and to flatten them out since they all had angles i dont even wanna show what we did to match the height of the header flange..... it was way different heights and hans didn't wanna grind on his 300 manifold any more Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 not to mention how straight the runners are .... Quote Link to comment
jrock4224 Posted February 6, 2014 Author Report Share Posted February 6, 2014 these carbs were designed to be more "fuel efficient" thats why there are 6-7 progression holes in the tubes instead of 3-4 like dcoes they are supposed to help throttle response and driving so your able to drive at all speeds relatively smoothly no matter what position the throttle is at i love my carbs above 2k anything under that is pretty choppy also my car idles at 900-1000, i can bring it down to 650-700 but it way too lopey yeah i kinda went in assuming all this carbueration would be a little challenging and that it would kinda be rough .....but its not right at all .... right now i just need a starting point cuz where we are at is wron as fuck ... these came off a alfa like yours too or at least thats what i been told ... they look and smelled like they never been ran ever... Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 to help in the search these came stock on alfa's in the 80's Quote Link to comment
jrock4224 Posted February 6, 2014 Author Report Share Posted February 6, 2014 did u ever post your final jetting and set up onthat thread ... it kinda ended abruptly Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 lolz no i dont think so but ill get some numbers for you heres some stock info this is for the l20 with 40 dcoe's dont know if it will help but... i have 3 weber books and not one of the mention the dcom's... Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 float ball valve :150 air corrector's top and bottom: 160 idle jet : F60 main jet :138 pump jets: 35 and here's the odd man out emul. tube: f64 dcom's only came with i believe 3-4 diff. emul. tubs where the dcoe's have a bunch of different options Quote Link to comment
TENDRIL Posted February 6, 2014 Report Share Posted February 6, 2014 all 4 of my A/F screws are 1 1/2 turns backed off from bottom Quote Link to comment
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