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Author Topic:   JCC Carb step up springs
Mpcoluv
Gearhead

Posts: 945
From: Charlotte NC usa
Registered: Apr 2001

posted 03-10-2003 07:10 PM     Click Here to See the Profile for Mpcoluv   Click Here to Email Mpcoluv     Edit/Delete Message   Reply w/Quote
I know every body hates these things but it is only temporary....
The Edelbrock AFB step up springs are rated in inched of vacuum.
How does this relate to manifold vacuum at idle?
In other words can you select the step up spring based on manifold vacuum or only by trial and error?

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steve'66
Gearhead

Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000

posted 03-10-2003 10:16 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
I dunno, but I'll bump it up for you.

SteveW

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Fastymz
Moderator

Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001

posted 03-11-2003 01:11 AM     Click Here to See the Profile for Fastymz   Click Here to Email Fastymz     Edit/Delete Message   Reply w/Quote
I thought the springs were rated in ounces like 6,7.5,and 9 ounces.Which does not tell you alot about vacuum.But the lower the number the more easy they open.The #6 does lift at around 5-6 inches of vacuum and the others around 7-10 inches.But it is all done by trial and error.

I hope that helps some.

------------------
SCOOP
oddly obsessed with big scoops on little Mustangs

2.26 60'S
14.9 @ 90.86MPH

65 coupe,351w,C4,Big Boss 429 hood scoop,8"3.40 TracLoc,Cragar SS,Black Suede.

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itlbrnmoff
Gearhead

Posts: 746
From: Indianapolis,IN.USA
Registered: Nov 2002

posted 03-11-2003 07:32 AM     Click Here to See the Profile for itlbrnmoff   Click Here to Email itlbrnmoff     Edit/Delete Message   Reply w/Quote
Ok...here's where I might be able to help...
the springs are rated in inches of vacuum at idle.
Blue - 3"
Yellow - 4"
Orange - 5"
Pink - 7"
Plain - 8"
The base calibration is the orange spring which stages "rich" at 5" Hg.
At idle, engine vacuum pulls the spring and metering rod into the jet. Then, when accellerating and vacuum drops, the spring overcomes the vacuum and raises the metering rod out of the jet for the "power Mode"...rod down is the cruise mode.

This from the Owner's Manual.
If your vehicle has a driveability problem that is encountered as the throttle is gradually opened, but then goes away upon further opening,it may be possible to eliminate the "lean spot" by using a stronger step-up spring.
It is best to select a spring on the basis of vacuum readings, but in the absence of a vacuum gauge, try the strongest spring first, (highest vacuum rating) to see if the problem goes away.
If the drive problem is cured by the strong spring, try the next weakest spring as well.
If the strong one does not help, then the calibration problem is related to the A/F metering stage of either the cruise or power modes.
I guess this would apply to a Carter AFB also.

My experience with this carb is that nothing in the owner's manual worked when tried, only by trial and error did I ever get acceptable street manners.

My problem was a mid-throttle cough or bog, and I finally cured it by using smaller jets in the secondaries.

That's weird how an AFB uses smaller jets in the secondaries than in the primary side...
I guess it's because the secondaries don't have a metering rod that sits in the hole of the jet.

Here are the base calibrations for each model # of Edelbrock carbs.

Primary sec. metering rods
#1404 - 500cfm - .086 .095 6552
#1405 - 600cfm - .100 .095 7047
#1406 - 600cfm - .098 .095 7547
#1407 - 750cfm - .113 .107 7147
#1409 - 600cfm - .098 .101 6847
#1410 - 750cfm - .113 .107 7147
#1411 - 750cfm - .110 .107 7547

I still don't know how to make columns or format on a computer, this ended up different than when I was typing it...

------------------


Low Dollar 1983 Mustang GT W/T-tops...
306 4bbl. T-5 3.45 trac-loc...it'll burn 'em off
1988 Lincoln LSC
5.0 auto full power

[This message has been edited by itlbrnmoff (edited 03-11-2003).]

[This message has been edited by itlbrnmoff (edited 03-11-2003).]

[This message has been edited by itlbrnmoff (edited 03-11-2003).]

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Mpcoluv
Gearhead

Posts: 945
From: Charlotte NC usa
Registered: Apr 2001

posted 03-11-2003 08:06 AM     Click Here to See the Profile for Mpcoluv   Click Here to Email Mpcoluv     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by itlbrnmoff:

This from the Owner's Manual.

It is best to select a spring on the basis of vacuum readings, but in the absence of a vacuum gauge, try the strongest spring first,


But HOW do you select the springs based on vacuum? Use an 8"hg spring if you have 14" vacuum? I''l go by the trial and error method I guess......

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itlbrnmoff
Gearhead

Posts: 746
From: Indianapolis,IN.USA
Registered: Nov 2002

posted 03-11-2003 08:54 AM     Click Here to See the Profile for itlbrnmoff   Click Here to Email itlbrnmoff     Edit/Delete Message   Reply w/Quote
Yeah MP, that's the problem, what it says in the book doesn't work.
My engine has about 14" of vacuum at idle, and I'm using the orange 5" spring. When I changed to a stronger spring, 8", it just moved the cough to a different RPM.
What is your engine doing?
Cough, stumble, surge?
More than likely you'll need to experiment with jetting and rods and just use the orange spring.

But I guess it's the same principle as a Holley power valve, a 6.5 power valve should richen when the vacuum drops to 6 1/2".

------------------


Low Dollar 1983 Mustang GT W/T-tops...
306 4bbl. T-5 3.45 trac-loc...it'll burn 'em off
1988 Lincoln LSC
5.0 auto full power

[This message has been edited by itlbrnmoff (edited 03-11-2003).]

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