I have a stock 3tc that I have just put DCOE 40's on. I purchased the intake and linkage from BRD racing and plan many more upgrades when my wallet can afford them. When I told the engine builder my symptoms he said I would never be able to run the 40's until I had a cam put in it. My question is, is this true?
The engine runs fairly well at idle 700-800 RPM, but has lousy response. Absolutely no power. Can barley make it up the driveway. Doesn't seem to be loading up and the plugs are darker then I'd like but they aren't saturated. The carbs are freshly rebuilt. I haven't synced them yet either.
If what the engine builder says is true can you guys give me a jetting suggestion after I get a cam put in it? I understand that the cam will need to be tuned to the carbs depending on the lift and LSA I pick. A ball park idea would be nice.
Here is what I'm running now
33mm chokes
175 air corrector jet
F16 emulsion
115 main
50f9 idle jet.
I'm at sea level.
Thanks for the help.
DCOE tuning issues
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bubbajohnson
- Posts: 48
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Re: DCOE tuning issues
First, read this! The short answer is, yes, they will work, but not without the proper synching, jetting and tuning. Is it ideal to run DCOE's on a stock engine and cam, no it's not, but they are very adjustable, so long as you take your time to understand them. The jetting if it's close can be fiddled with a bit, however, they will never run right until you sync them, period.http://www.s262612653.websitehome.co.uk ... webers.htm
Re: DCOE tuning issues
If you dont synch them you cant even adjust them because they are not running the same. If you are going to tune them yourself you should get an air fuel ratio meter. If you have no power you might be running very lean, not good for the engine. Looks like you are running jets for 28 mm venturis. Parts are expensive for these carbs so make sure you know what you want to do before spending more money. Remember everything you do to the engine will affect the carbs = more jets and parts for 4 carbs. So you can try to make them run stock or wait to get the cam and go from there.
Re: DCOE tuning issues
Yes you can run those on a stock engine. Obviously with a better cam they will both work to give you more power. But they are just carbs and can run at any engine spec.
Check your float levels. Make sure the floats have the correct amount of droop........15mm I think for Webers. When you close them there should be a gap between the top of the float and the underside of the carb of about 7-8mm once the valve has closed. It's easier to check than it sounds once you remove the top of the carb. If the float level is too high it will flood and feel like it's running on choke, especially as you say the plugs are black. If it's way too low the bowl level will be below the emulsion tube holes and the mixture will be far too weak.
There are 3 stages to tuning sidedraught Webers or Dellorto's.
Firstly you need to get the float levels right and matched. Then you can work on getting it to idle via the idle jets and getting it balanced between the carbs.
Secondly is what happens when you come off the idle stage as you put your foot down. This involves the pump jets. If they are too small it will hesitate before it picks up again but too rich can also cause this flat spot. I reckon about 35 pump jets.
Thirdly is what happens when you are running flat out.....getting the main jet and air corrector sizes correct. An AFR here is really handy but if you know how to read plugs you can get very close. To get to this stage the previous two have to be right.
It looks to me like your main jet is WAY too small for that air corrector. The air corrector looks about right....I would be trying a 140 main jet with those. Your chokes should be fine, your F16 emulsion tube is about right. 50F11 maybe 50F9 but we are splitting airs.
The thing is that you need to get it to idle FIRST........then you go to the pulling away stage.........and once it pulls away nicely you go to the Mains.
There is a great book out there by Desmond Hamill on "Power tuning Weber and Dellorto sidedraughts" and once you understand it then you actually see how simple they are.
Right now it just seems like a mass of jet sizes and figures..........but it does get to be understandable!
Check the float levels first, change out that main jet and take it from there.
Best wishes,
Brian
Check your float levels. Make sure the floats have the correct amount of droop........15mm I think for Webers. When you close them there should be a gap between the top of the float and the underside of the carb of about 7-8mm once the valve has closed. It's easier to check than it sounds once you remove the top of the carb. If the float level is too high it will flood and feel like it's running on choke, especially as you say the plugs are black. If it's way too low the bowl level will be below the emulsion tube holes and the mixture will be far too weak.
There are 3 stages to tuning sidedraught Webers or Dellorto's.
Firstly you need to get the float levels right and matched. Then you can work on getting it to idle via the idle jets and getting it balanced between the carbs.
Secondly is what happens when you come off the idle stage as you put your foot down. This involves the pump jets. If they are too small it will hesitate before it picks up again but too rich can also cause this flat spot. I reckon about 35 pump jets.
Thirdly is what happens when you are running flat out.....getting the main jet and air corrector sizes correct. An AFR here is really handy but if you know how to read plugs you can get very close. To get to this stage the previous two have to be right.
It looks to me like your main jet is WAY too small for that air corrector. The air corrector looks about right....I would be trying a 140 main jet with those. Your chokes should be fine, your F16 emulsion tube is about right. 50F11 maybe 50F9 but we are splitting airs.
The thing is that you need to get it to idle FIRST........then you go to the pulling away stage.........and once it pulls away nicely you go to the Mains.
There is a great book out there by Desmond Hamill on "Power tuning Weber and Dellorto sidedraughts" and once you understand it then you actually see how simple they are.
Right now it just seems like a mass of jet sizes and figures..........but it does get to be understandable!
Check the float levels first, change out that main jet and take it from there.
Best wishes,
Brian