Thread: 48 IDF jetting.
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Old 08-14-2009, 01:02 AM
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Caprimaniac Caprimaniac is offline
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Join Date: Sep 2006
Location: Skjetten, No
Cobra Make, Engine: Unfortunataly ; none
Posts: 333
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Default After sun comes rain

Or after boilings comes ice.

Did a couple of hours with broadbandmeter last night. A/R abaout 11.5 at full throttle. Too rich, I know.

Did some reading and found a formula: Main venturi *4= main jet size= 160
I did put in 165, so that's a fit.

But then: Air corr.= main jet + 60 = 225... I have 190 (drilled to 200...)

Will try to change to 135 mains; fits the formula. Will get a set of 225 or 230 later to go with 165.

Also:
Went autocrossing last weekend. Bubbling sound and hestiation at around 4000- 4500.
Drove to pit & parked. Had a feeling of boiling gas in the float chambers (as I previously have experienced.) But no; THE CARBS WERE ICE COLD.

Same happened last night; after going through 2. and 3. to 7500 rpm, the engine stalled in 4. @ 4000 rpm.

After parking, again, carbs icecold...

Conditions: Humid (rainy), 52 F (11 deg. C). At autocross it was not that cold, but same humidity. Have a large front scoop and "double hood" with a closed chamber surrounding the air horns of the carbs.

And, in addition to the icing this happend: After 1 hour of highway speed (60 mph) my gastank went empty! Wow! I cannot see going up +030 in a mainjet can cause this, but....

Can someone confirm: Can carb icing be the cause of the hesitation in 4. at around 4000 rpm?
I will try some alcohol in the tank to see if that helps. Any other ideas?

Also: Sudden explosion in gas consumption. Can icing conditions be the reason?
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