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So what I'm looking for is an initial setup. Primary & secondary throttle plate position. .020" on the primary and match the amount opened on the secondary?
Engine is a Ford FE, 10:1, Comp 282S cam, Edelbrock heads & intake, headers, etc. About 11-12 inHg vacuum at 750 RPM. What I'm trying accomplish is getting the idle & cruise AFRs set.
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It isn't that critical.
Hold the throttle up to the light, and make the secondary just short of the primary.
This is a vacuum secondary carb, two corner idle, and no replaceable bleeds.
It pulls fairly good vacuum, I would be more concerned if the camshaft was larger. Gary
Last edited by Gaz64; 11-13-2019 at 02:01 AM.
Regards, Gary
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Time to revisit.
AF ratios as follows; 13.5-14.0 @ idle. 13.5 @ cruise. However 15.5-16 @ WOT. Primary jets are 72 and secondary are 78. I have also removed the ball bearing from the vacuum secondary diaphragm (secondaries now just seem to flop open with taller yellow spring). Does this affect the AFR? I'm going to return the ball bearing to it's rightful home. Ideas? Jet up secondary? How much? Thanks, Robert.
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Wide open is engine destroying lean if that is correct.
What are using to determine that A/F ratio?
Have you looked at your spark plugs?
What size fuel line?
What fuel pump, filters, etc?
Yes, a too early, flopping opening secondary gives a lean bog. The engine struggles to pull fuel if the venturi signals are weak.
Regards, Gary
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Wide open is engine destroying lean if that is correct. Yep!
What are using to determine that A/F ratio? Innovate AFR meter bung just past header collector.
Have you looked at your spark plugs? No.
What size fuel line? 3/8"
What fuel pump, filters, etc? Holley manual through Holley regulator set @ 6-7 lbs.
Yes, a too early, flopping opening secondary gives a lean bog. The engine struggles to pull fuel if the venturi signals are weak. Is it the small or large ball bearing? I will replace.
Thanks so much for your responses.
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That all sounds like a good setup so far.
Your carb sounds jetted OK at 72/78.
Factory spring is Plain.
Ball bearing needs to be smaller than hole bore, to allow airflow in both directions.
Slow opening, past the seat where the groove is, then fast as the ball unseats, to allow the diaphragm to follow a fast closing throttle.
Regards, Gary
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I'll get the ball bearing replaced and return to the plain spring (I was running a purple). Will report back. One change at a time.
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Yes, one change at a time.
Regards, Gary
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OK, today's change. Replaced small ball in vacuum diaphragm and replaced tall yellow spring for plain spring. Secondary kick not nearly as noticeable, WOT AFR now at 13.8-14. Next? Thanks, RY.
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Do you have any jets? Take all four up by two, to 74/80 to start. Gary
Regards, Gary
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