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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 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? IP: Logged
steve'66 Gearhead Posts: 6522 From: Sonoma,CA,USA Registered: Mar 2000	posted 03-10-2003 10:16 PM I dunno, but I'll bump it up for you. SteveW IP: Logged
Fastymz Moderator Posts: 11429 From: Reno Nv USA MEM#1240 Registered: Apr 2001	posted 03-11-2003 01:11 AM 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. https://mustangsandmore.com/ubb/Fastymz.html IP: Logged
itlbrnmoff Gearhead Posts: 746 From: Indianapolis,IN.USA Registered: Nov 2002	posted 03-11-2003 07:32 AM 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).] IP: Logged
Mpcoluv Gearhead Posts: 945 From: Charlotte NC usa Registered: Apr 2001	posted 03-11-2003 08:06 AM 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...... IP: Logged
itlbrnmoff Gearhead Posts: 746 From: Indianapolis,IN.USA Registered: Nov 2002	posted 03-11-2003 08:54 AM 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).] IP: Logged

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