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When cold it ticks over fine, sits at about 500/600 revs first thing in the morning and then slowly comes up to about 900/1000 revs once the engine is up to temperature. I have checked the float level, twice actually lol, I did some checking around and set it to 8.5mm (did this with a drill bit to mesure the gap). The fuel boiling was the first thing I thought when this started but I've experienced that before with a type 4 I built once with 40IDF's and when it boiled you could here it boiling and see vapour on top of the throttle inside the throats. I'm not seeing or hearing any of those things here. As to the hot air I've already had the thought to make an aluminium shield to help but wonder how much that's really going to stop. Other than that I thought to get a plenum made up to then have a large cone filter at the front of the bay, the problem is it would end up behind the rad fan which pulls cool air in the rad and all the warm air is pulled into the bay so will there for end up in the air filter which just puts me back to the beginning. Just to get this straight are you suggesting a fuel return to the tank could be needed? Also that an electric pump may help over the mechanical one I'm using now? I defiantly think my main problem is excess fuel and that its bleeding from the chokes and working to keep the car running when cool but then when warm/hot all it's doing is wetting the plug/plugs where it can't burn it an causing it to try cut out but I really appreciate all your input and please keep them coming as they all something to think about and test and try ??
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May 26, 2015 12:07:34 GMT
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Hello. I have just spent an age getting my weber dcoes running right, and one of the issues I had, which gave exactly the same symptoms, was that the engine motion at idle was causing the fuel in the float chambers to froth up. Slackened up the nuts holding the carbs on, loosening up the rubber washers, and problem solved.
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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May 26, 2015 17:06:23 GMT
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On a Mini a friend bought a heat shield and wrapping the fuel lines with some wrap cured his issues. A garage told him he had a vacuum forming in the tank :/. Considering my MGB had this problem and never had an running issue I found it hard to believe.
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May 26, 2015 17:23:18 GMT
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Hmm that idea with the fuel frothing because they may be to tight is an idea as I didn't really know how much to tighten them so went as much as I could with some lock tight so yeah might try that thanks!
Yeah not sure what good if much a head sheild will really do as the carbs will still be absorbing heat from the head
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May 26, 2015 18:00:55 GMT
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I have got a gap of about 2mm between the two cup washers that sandwich the rubber washer. If you are not using nyloc nuts, you have got no hope. Good luck, hope it helps.
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May 26, 2015 19:05:55 GMT
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I'm not using nuts at all, couldn't get the carbs on with the studs so had to use bolts with lock tight. Thanks
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bigdaz
Part of things
Posts: 201
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Get set up on a rolling road, these carbs are universal and set up for each application, there's choke sizes needle valves emulsion tubes jets all have to be the right size to get the most out of the engine, it's well worth the money
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It could be the cold start device leaking as suggested but it could also be too high fuel pressure.
I see you have a regulator fitted but what pressure is it set to? It should be 2.5-3psi only. Any more than 4psi risks flooding.
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Jun 12, 2015 17:24:17 GMT
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Would like to get it on a rolling road but it's finding one I can trust also the funds won't allow it right now haha. I've got a base line jet set up from redline in the states who I deal with quite a lot and by some of what they've said I could actually be running to small jets in some places so going to change them out while I block the chokes off. The pressure doesn't seem to ever go over 3psi but I haven't actually seen what it does when it starts trying to cut out, also I haven't yet had the chance to pull the plugs when it starts playing up to see if their getting wet. But got a few things to try now and hopefully it solves the problem. Really appreciate everyone's suggestions and help!
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dyno
Part of things
Posts: 14
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Jun 12, 2015 19:57:12 GMT
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Ok, its probably flooding . The co meter should have shown a rich mixture. The reasons are:- 1.too high fuel pressure,2. too high float level, 3.worn float needle valve,4.too large venturi size,5. choke mechanism sticking,6. holed float. Whilst its idling get a mirrio and look down the carb venturi and after a while you will see fuel dripping or collecting in the venturi. Its then down to you or someone that knows how, to sort it, but a dyno session is the only away to know its right.
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j4m35
Part of things
Posts: 70
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I'm not using nuts at all, couldn't get the carbs on with the studs so had to use bolts with lock tight. Thanks You've bolted them directly to the inlet manifold with no thrackery washers or rubber bobbins? No wonder!
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What do you mean by thrackery washers and rubber bobbins mate? I'm running the rubber/metal gaskets and used lock tight on the bolts so I didn't have to lock them down tight. To be honest it was such a pain doing it with bolts I'm probably going to change them for some short studs anyway.
Flooding is what I first thought and at first it was but that turned out to be the float level was completely wrong so I corrected that ages ago and have checked it since when I changed my needle valves and now when I look down the venturies there isn't any excess fuel sat on the throttle plate or in the venturies. The one that still makes sense to me is fuel bleeding through from the chokes, so under the throttle plate. It makes sense, so when it's cool it uses it like a choke to keep running but once warm it no longer needs that fuel. It doesn't play up while I'm driving because it's still able to burn it off or shoot it straight out the exhaust but once I'm sat still for an amount of time that extra fuel builds up in the cylinder and dampens the plug causing it to run on less cylinders and try kill it but then once I get moving again the heat from the engine and the speed it starts turning burns off that extra fuel and drys the plug back up making it run on all four again.
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j4m35
Part of things
Posts: 70
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DCOE carburetors should be completely insulated from the inlet manifold by the rubber sandwich plates and rubber or sprung anti-vibration methods on the studs. The only function of the studs / nuts is to keep the whole ensemble under just enough tension to prevent the carbs falling off or the sandwich plates leaking.
Google it, there are kits available.
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dyno
Part of things
Posts: 14
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Jun 13, 2015 10:42:27 GMT
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The carbs need to float, the reason is to stop fuel frothing due to vibration .If the choke is sticking you would usually hear a hissing .
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Jun 18, 2015 16:01:49 GMT
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The cold starts don't just stick they leek like an incontinent rugby sqaud....
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Been having a look around at other peoples builds when I go to shows and noticed everyone using a particular style washer that has a rubber centre. I didn't realise I had to use these as I'm more used to IDF webers from working on air cooled dubs. Going to buy myself a set and some alankey head bolts to make fitting easier and fit them when I pull them back off to bung the chokes/cold starts up. Cheers for your help guys
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frag
Part of things
Posts: 335
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The ones you've seen are most likely 'misab' plate/washers.... Usual method of mounting sidedrafts to manifold.
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'69 Holdsworth bay '88 T25 Panel van ‘72 beetle ‘78 vw champagne T2
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Spoke to dellorto UK and they call them cosworth washers so I've got a set on their way. Also I think I've found my problem, I blew my inlet gasket the other night on the way back from a meet, I took everything off yesterday to change it and when I took the gasket off it was broken in several places, quite deteriorated and stunk of fuel, so I believe it got soaked when I first fitted the carbs and was massively over fueling from the floats and pressure being wrong and since then every time it got warm/hot it opened up a tiny air leak causing it to try cut out. But once cool again the leak would close up just enough. Anyway it's all back on now and seems okay just need a bit more tweaking on the tuning. Will post again if anything changes
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