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Kirkham Motorsports

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  #21 (permalink)  
Old 04-17-2013, 05:20 PM
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Nice. You need to drill the holders to get the in between size. I had to.
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Old 04-17-2013, 08:21 PM
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Got in 2 test drives this afternoon with the 120 holders, 1st drive with idle mix set to 12.5-13 A/F, lean idle. "Punching" it moderately showed mixture going lean with the stumble, and much backfire when backing off the gas. 2nd drive with mix set rich 10-11 A/F, but smoother, Punching it showed mixture also going lean (15-16) but no backfire when off the gas. At this point I would surmise it needs a larger pump shot ? Carbs had blocked pump valves when I got them , but were replaced with .50's. I think I'll try advancing the initial timing first. Zrayr: just read the info you showed, very interesting.
I'll report results as soon as I have some!
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Old 04-17-2013, 08:26 PM
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13: 100 holder is that "point" 1, or 1/10th mm? I'll see if I can get close to that with my # drills.
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Old 04-17-2013, 09:07 PM
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Quote:
Originally Posted by MOTORHEAD View Post
".............. Carbs had blocked pump valves when I got them , but were replaced with .50's. I think I'll try advancing the initial timing first. Zrayr: just read the info you showed, very interesting.
I'll report results as soon as I have some!
Did you run it at all with the 00 acc. pump bypass valves ? I have 60's now and am thinking about doing some experimenting in that area.

My 10 & 14 degree bushings are on the way. We'll see if I have any benefit. Right now the car seems to like 22 initial timing best as far as idle quality goes. A lot of my off idle stumble went away with going to the lightest dist. springs, but sometimes the idle will hunt a bit with them. It just starts advancing too soon, so I'm trying the next lightest combo.

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Originally Posted by MOTORHEAD View Post
".............When I mentioned A/F meter to Inglese he said " do you want it to run right, or do you want to chase numbers?"
I want both, as much as possible. I realize there exceptions and trade-offs.


Ha ha, he's said much the same thing to me. He's right about one thing, you can get the best performance out of a set of Webers when they "appear" by the numbers to be running a bit rich (especially on the low end). Just my experience so far.

Z.
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Last edited by zrayr; 04-18-2013 at 06:26 AM..
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Old 04-18-2013, 03:21 AM
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Quote:
Originally Posted by MOTORHEAD View Post
13: 100 holder is that "point" 1, or 1/10th mm? I'll see if I can get close to that with my # drills.
A 100 jet would be 1mm. Just like a 60 idle jet is .6mm.

The numbering is in 1 hundredths of a millimetre. 100 hundredths of a 1 millimetre = 1mm.

An industry standard for any metric jetted carburettor.
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  #26 (permalink)  
Old 04-18-2013, 07:34 AM
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Motorhead

try 75 idle with 120 air
Im betting on 80 idle with 130 to 135 air
Mixture screws about 1 to 1 1/8 turn open.

air fuel ratio at idle when engine warm should read around 11 to 12 AF.

Last edited by carmine; 04-18-2013 at 07:42 AM..
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Old 04-18-2013, 07:28 PM
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All cobra work has stopped while the house is being painted. Wil check back in couple of days. Thanks for all the help.
Ted
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Old 04-25-2013, 11:02 PM
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My KC482 runs rich according to A/F ratio meter. between 11.5 (idlle) and 12.6 most of the rpm range. But the plugs look good, light brown. So the A/F meter is not so precise, at least on these engines.

Idle screws are 1,5 turn out specially to prevent popping from the exhaust.
I am running 21 initial and 38 max. Have made myself a special larger stop bush which is oval, otherwise it will not fit into the distributor placement for it.
I have 65 idle jets with 100 idle holder. tried 120 . ran leaner (around 13 A/F) but transition was not as smooth. Maybe 110 would be an option to try.
Main is 155 with a self made emulsion tube, F11 also ran good. Important is to have a small air jet, I use 120,(carb comes with 210) in order not to lean out on WOT.
Chokes are 40mm , 37mm were impossible to tune well on mine.

Pump bypass is 00 now, and will check if a .35 bypass will do away with the black cloud my friends tell me I shoot out the exhaust when accelerating hard.
Engine runs smooth, transition is spotless.

EFI will give you better mileage, but the instant response of the Webers will not be there.

And I just do not want electronics in my Cobra.
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Old 04-26-2013, 12:16 AM
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"EFI will give you better mileage, but the instant response of the Webers will not be there."

"And I just do not want electronics in my Cobra."

AMEN to that!
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Old 04-26-2013, 07:17 AM
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Eljaro wrote
"black cloud my friends tell me I shoot out the exhaust when accelerating hard."

Sounds like you might be sucking oil out under hard acceleration.

Eljaro
Are you running pcv?
If so where is it connected to?

Last edited by carmine; 04-26-2013 at 07:22 AM..
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Old 04-26-2013, 09:13 AM
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Motorhead:

If you do not have metric drills a combination of miniature "Numbered" and "Lettered" drills will work just as well, you'll need a conversion chart.
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Old 04-26-2013, 11:32 AM
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Quote:
Sounds like you might be sucking oil out under hard acceleration.
That would produce blue smoke.
Black smoke is too rich or unburned fuel
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  #33 (permalink)  
Old 04-26-2013, 11:46 AM
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Un burnt fuel mixed with oil will come out as dark grey

Can easy be mistake for nothing but rich

is your pvc connected to vacuum on intake, carb or exhaust header?
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Old 04-27-2013, 12:56 AM
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no PVC here with Weber manifold. Crancase fumes go into a catch tank and then out into the air.
Exhaust soot is black, not dark gray, so only gasoline in excess when pump comes in.
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Old 04-27-2013, 08:40 AM
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Ok
Defanetly fuel then
For your cubics I would change to

80 idle
130 idle air
This will allow you to close idle mix screws to about 1 to 1 1/8 turns open

Main 165
Main air 180

Pump jet .5
Pump exhaust .6 to .8

You may not agree but....
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  #36 (permalink)  
Old 09-21-2013, 02:17 PM
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Quote:
Originally Posted by carmine View Post
Ok
Defanetly fuel then
For your cubics I would change to

80 idle
130 idle air
This will allow you to close idle mix screws to about 1 to 1 1/8 turns open

Main 165
Main air 180

Pump jet .5
Pump exhaust .6 to .8

You may not agree but....
Well, I am always willing to experiment and improve engine response with the webers.
Do you have this setup in your car or is this experience setting up Ford BB's with Webers?
A 75 idle jet with the 120 idle air (which is what I had in my jets box) worked very well, no more sneezing out the carb and idle mixture quite close to ideal A/F ratio. Before going on and purchasing any extra jets I would like to know how you arrived at the above settings.
Thanks
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Old 09-19-2016, 02:21 PM
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Eljaro wrote:

"Do you have this setup in your car or is this experience setting up Ford BB's with Weber's?"

Hello Eljaro.
Sorry for the really late response.
Yes i have this set up in my car.
As for my experience, like most with Weber's, its all calculated trial and error.
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