Weber Jets DCOE 8V TC

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156_WALLA
Posts: 6
Joined: January 12th, 2012, 6:56 pm

Weber Jets DCOE 8V TC

Post by 156_WALLA »

Hi Guy,
I have searched your forum and the internet but I am struggling to find the info I need regarding the recommended DCOE 40 side draft set-up for a 2.0 TC 8V in standard configuration.

The problem I have at present is the idle is lumpy and the initial throttle response is erratic. I have tried to set-up using color tune, at idle I appear to get a strong blue flame, occasionally it seems to miss a beat and occasionally you get a yellow/orange flame, this effect seems consistent across all 4 cylinders.

I also notice that with the colortune: if I open up the throttle the flame goes from blue to orange and then after a few seconds stabilizes and turns blue.

Useful info
Carbs have been stripped and cleaned
carbs balanced
No carb leaks (fuel)
throttle shaft bearings are sealing well
3 progression hole type carbs
Floats set to 12mm both carbs are equal
Pump jet mechanism stripped and cleaned (was sticking previously)

Engine is in a Seven kit car so load is minimal

Existing Jets
32mm chokes
Idle Jets : F955
Emulsion tube: F11
Main jets: 125
Air correctors: 195
Pump jet: 45
idle screws out 2 turns +/-1/4 (idle set using colortune)
GaryR
Posts: 9
Joined: May 22nd, 2011, 9:00 am
Location: Leicester. UK.

Re: Weber Jets DCOE 8V TC

Post by GaryR »

Hello. My tuppence worth if I may. About 27 years ago I owned a standard 2L 131 Sport. I had the exact same set up of 40 DCOE's with 32mm chokes. The car had an annoying flat spot whenever it accelerated and no matter how much I altered the jetting it wouldn't cure it. So what I did was returned the jetting settings to how they were originally before I tinkered but fitted 30mm chokes instead. Result, the engine responded perfectly with no flat spot or hesitation whatsoever.

Now as far as the idle mixture screws are concerned, 2 turns out from what I remember with mine is not enough. I'm sure mine were at least 4-5 turns out. Set the engine to correct idle speed and turn each idle mixture screw in or out (probably out in your case) until you notice the idle speed increasing and stop. You may notice a smoother tick over after too.
I've never used a colourtune and never yet needed to although they must be good because I think Guy uses them.

Also to add, make sure you have good fuel pressure!

I hope some of this helps a little. Good luck!

Gary.
GaryR. Book #104/500
Guy Croft
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Re: Weber Jets DCOE 8V TC

Post by Guy Croft »

The ignition timing needs to be checked, should be 10 deg at idle - 850rpm.

As far as jetting - my recommended changes in bold:

Existing Jets
32mm chokes
Idle Jets : F955 45F9
Emulsion tube: F11 F16
Main jets: 125 140
Air correctors: 195 180
Pump jet: 45

it may be simply that the carbs are out of balance, the most common cause of 'lumpy' idling, buy a balance meter from Webcon or 'Carbalancer' from Gunson if you don't have a suitable device. Normally DCOE have individual air bleed screws so you can adjust barrel-barrel on each individual carb. One screw must be closed and that will be on the highest flowing barrel.

Before attempting balancing it is vital to ensure that the throttle plates do close fully (with idle speed screw fully unscrewed) and that the springs on the throttle mechanism do actually control them effectively.

Balance affects idle mixture and vice-versa so it takes several hours to perfect the settings. You must get the engine bay to full operating temperature and check the final settings after road testing.

G
Attachments
DCOE 40_air bleed screw.JPG
DCOE 40_air bleed screw.JPG (54.92 KiB) Viewed 11335 times
Synchrometer
Synchrometer
syncrometer.jpg (9.81 KiB) Viewed 11335 times
Guy Croft, owner
156_WALLA
Posts: 6
Joined: January 12th, 2012, 6:56 pm

Re: Weber Jets DCOE 8V TC

Post by 156_WALLA »

Hi Guy,
Thanks for your response i will try as you recommend, however I have tried the timing at 10 degrees BTDC but it runs awful. Its set at 16 degrees, i am using megajolt system with edis4. I did get to the point where i took the crank pulley off to check all my timing marks to be 100% sure TDC was TDC.

Maybe if i am over fueling with the idle jets i need more advance to get a decent idle?

Either way i will try your suggestions.

Thanks again for your time.
Guy Croft
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Re: Weber Jets DCOE 8V TC

Post by Guy Croft »

it won't run well with 10 deg because the carb settings are not right - most likely out-of-balance.

Reset it to 10 deg to do your carb tuning. I have seen this before, she should settle down if you go thru my regime..

G
Guy Croft, owner
156_WALLA
Posts: 6
Joined: January 12th, 2012, 6:56 pm

Re: Weber Jets DCOE 8V TC

Post by 156_WALLA »

Hi Guy,
I have tried the following tests

1. Kept the 55F9 jets in place and set the timing to 10 advance. Took it for a drive and it was very rough and somewhat powerless, set it back to 15 advance and it was like a different engine, (quick)
2. Kept the static at 15 degrees and changed the jets to 45F9. Upon acceleration the engine bogged down heavily
3. Kept the 45F9 and tried it at 10 degrees. Could barley get off the drive.

I am begin to wonder if my engine has non standard cams in it.
GaryR
Posts: 9
Joined: May 22nd, 2011, 9:00 am
Location: Leicester. UK.

Re: Weber Jets DCOE 8V TC

Post by GaryR »

Try a strobe light on your timing marks if possible. Make sure the timing mark on the crankshaft pulley is steady and not bouncing around at 10 degrees idle and then make sure the timing mark will advance when throttled slightly.

Just an idea!
GaryR. Book #104/500
Guy Croft
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Re: Weber Jets DCOE 8V TC

Post by Guy Croft »

... could be an exhaust back-pressure problem. What is on there?

G
Guy Croft, owner
156_WALLA
Posts: 6
Joined: January 12th, 2012, 6:56 pm

Re: Weber Jets DCOE 8V TC

Post by 156_WALLA »

It has a standard exhaust manifold with modified down pipes that tapper into a singe outlet under the engine. From there on its straight through via a 48mm internal bore silencer.

4-2-1

I guess the back pressure is very low due to zero exhaust baffles.
Simon
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Re: Weber Jets DCOE 8V TC

Post by Simon »

Going back to GaryR's point, have you actually verified the actual timing point of the spark, or just assuming it from the static reference for the Megajolt/EDIS? Just a thought.
GC_15
156_WALLA
Posts: 6
Joined: January 12th, 2012, 6:56 pm

Re: Weber Jets DCOE 8V TC

Post by 156_WALLA »

Hi Simon,
I fully checked the timing marks previously, to the extent of pulling off the pulley wheel and checking the mark on the wheel against the mark on the block ( I had reservation of the mark on the pulley against the marks on the cambelt cover). Zero is definitely Zero.

I also checked that the timing advance the megajolt was putting out was also accurate. Cam positions checked too.
GaryR
Posts: 9
Joined: May 22nd, 2011, 9:00 am
Location: Leicester. UK.

Re: Weber Jets DCOE 8V TC

Post by GaryR »

Two simple things to check. All spark plugs are okay regardless of whether they are new and if the camshaft pulleys have been removed at any time, make sure they have been refitted to the correct camshaft.
GaryR. Book #104/500
156_WALLA
Posts: 6
Joined: January 12th, 2012, 6:56 pm

Re: Weber Jets DCOE 8V TC

Post by 156_WALLA »

GaryR wrote:Two simple things to check. All spark plugs are okay regardless of whether they are new and if the camshaft pulleys have been removed at any time, make sure they have been refitted to the correct camshaft.
Thanks Gary i will check this. What are the identifying marks for the camshaft pulleys inlet vs outlet? I know both holes on them align with the marker on the cam housing when at TDC
GaryR
Posts: 9
Joined: May 22nd, 2011, 9:00 am
Location: Leicester. UK.

Re: Weber Jets DCOE 8V TC

Post by GaryR »

There should be a letter 'A' stamped on the inlet pulley and a letter 'S' stamped on the exhaust.

If the engine has been left completely standard it's an unlikely mistake but always worth checking for elimination purposes.
GaryR. Book #104/500
Guy Croft
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Re: Weber Jets DCOE 8V TC

Post by Guy Croft »

a trip to GCRE would be worth it..

you'll pay - but it would be worth every penny.

G
Guy Croft, owner
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