air bleeds,main metering - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 8 Old 02-14-2016, 10:01 AM Thread Starter
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air bleeds,main metering

If i understand this correctly. A larger air bleed will delay the onset of the main circuit.
But what about total flow at wot ?

In my case 84 mains .026 air bleeds. If i bump the primary air bleed
to .028 would this have the same relative effect as decreasing the main jet ?
I like the idea delaying the main for better driveability/economy,
but need to have a better understanding of what happens at wot ?


427 T56 3.90 2 kits
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post #2 of 8 Old 02-14-2016, 11:12 AM
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WOT will be leaner and it does delay the main circuit but usually you want to bring on the main circuit and get out of the idle circuit for fuel economy and work with the power valve channel restriction for best WOT power What size carb and what size motor will help to determine the best calibration. 84 jet makes me think a 750 or larger carb. Don't use a secondary PVCR set the jets only and primary side you want the idle screws around 1.5 turns out

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post #3 of 8 Old 02-14-2016, 02:22 PM Thread Starter
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Copied,condensed 3 posts,from elsewhere. 427 Street car,trying to make it civil as possible.

The big Holley HP 1000,was giving me fits. Set the mixture screws for a clean idle (about a 1/2 turn out x4) and it would idle at 1100 + with the idle screw backed completely out. This was with the black bushing in the MSD distributor and the stiffest springs. About 17 initial 33-34 total,all in around 3600 (slow) Trying to bring the timing in quicker with lighter springs,made the high idle problem even worse. I have about 10'' vacuum at 1k.

Long story short,swapping the stock drilled throttle plates for solid ones and 79 idle air bleeds,has the motor returning to idle nicely. Currently using 2 blue springs,all in around 2500. Not perfect yet,but a lot more fun to drive.


Jetting is 84-84. Dropped 82's in the primary. Hard to explain the improvement in driveability. Pulling away (smoothly) from a stop,has become much less of a chore. Able to cruise at 1500 in 5th,if need be.

For comparison,on day 1 the car was unhappy at anything less then 2300.

Will try bringing the timing in a little quicker next (blue/light silver) all in around 2k.(no vacuum advance) Maybe drop the primary some more,or larger air bleeds ?

I am thinking with more moderate temps,40+ 81 primary and more pump shot. (.031 now) would be worth trying ?

A question about holley jets. #84=.099 #85=.0985 Could the 85 flow more fuel ?

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post #4 of 8 Old 02-15-2016, 10:36 PM
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Quote:
Originally Posted by JB Books View Post
If i understand this correctly. A larger air bleed will delay the onset of the main circuit.
But what about total flow at wot ?

In my case 84 mains .026 air bleeds. If i bump the primary air bleed
to .028 would this have the same relative effect as decreasing the main jet ?
I like the idea delaying the main for better driveability/economy,
but need to have a better understanding of what happens at wot ?
It will delay onset slightly, will also lean out the higher airflow area. (Higher rpm)

If you use a wideband and datalog, you can really see its affect in high gear....

1984 GT, 363 -RHS215 heads & Super Vic intake by MCRP, FTI cam, Carbureted, Glide, 4.30's, pump gas, street legal, N/A
Bests:1.35 60' / 6.21 /9.76 and 138.8 mph.
Thanks MCRP, UCC, FTI, Sepanek, Braswell, Racecraft, and Team Z
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post #5 of 8 Old 02-16-2016, 10:12 AM
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I think this carb does not come with power valves,only a plug so what I think you need to do is drill a power valve channel restriction of .0625 and then install a power valve of 5 inches of vacuum. Then you need an 84 jet in the secondary side and a jet that measures about .079 on the primary side which is probably a 77 or 78 jet. What is happening is too much fuel when you drive normal and when you add the power valve it separates normal from hard driving.
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post #6 of 8 Old 02-16-2016, 10:18 AM
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usually when you remove the power valve you jet up 6 to 8 sizes so you are adding the power valve on the primary side and jetting down 6 to 8 sizes
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post #7 of 8 Old 02-16-2016, 11:45 AM Thread Starter
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Holley 80513-1
Down leg booster
power valve 6.5
primary 84 jet .031 pump nozzle
secondary 84 jet .036 pump nozzle

.032 .033 and .035 nozzles on the way.

Installing the 82 primary made a unbelievable change for the better.
In both driveability and acceleration. The way it quickly snaps the tires
loose on the gear changes,rather then the delay i was feeling. (lift and stab)

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post #8 of 8 Old 02-16-2016, 05:38 PM
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I done a hsab swap on mine not long ago from 36 to 31 on my q750. It was goin flat on the shift an off the t brake. The swap solved my issues an was .2 richer at wot


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