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#1
11-30-2005, 01:34 PM
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Carter 4759 625 Competition Jetting?
Does anyone know what the stock jet/rod combo is on a Carter 625 Competition Series manual choke 4759s? I have a used one and don't know if someone has had there way with the internals or
not. Would one of these work good on a near stock 389?
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68 GTO,3860# Stock Original 400/M-20 Muncie,3.55’s 13.86 @ 100 Old combo: 462 10.75 CR,,SD 330CFM Round Port E's,Old Faithful cam,Jim Hand Continental,3.42's. 1968 Pontiac GTO : 11.114 @ 120.130 MPH New combo: 517 MR-1,10.8 CR,SD 350CFM E's,QFT 950/Northwind,246/252 HR,9.5” 4000 stall,3.42's 636HP/654TQ 1.452 10.603 @ 125.09 http://www.dragtimes.com/Pontiac-GTO...lip-31594.html |
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#2
12-01-2005, 08:14 AM
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4759 stock jetting is: 0.095" pri/0.086" sec jets. Rods are# 16-544: 0.0715"/0.058"
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#3
12-01-2005, 08:16 AM
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Yes, a friend of mine has that exact carb on a 400. He's using the RPM intake with a 1" three hole spacer. The secondaries have been richened to 0.095"
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#4
12-01-2005, 08:36 AM
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These are great carbs. Possibly a little rich in places for a stock 389. If you have a bog when the secondary kicks in, replace the airvalve with one from the original Pontiac AFB.
Jon.
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"Good carburetion is fuelish hot air".  "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
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#5
12-01-2005, 09:58 AM
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Thanks for the replies. It looks like mine is still stock. Those seem like pretty lean jets on the secondary side.
I don't have a Pontiac AFB to get an airvalve from. The one in this carb is angled so much it looks like it's starting to open. If I get a bog would it help if I modify the airvalves' stops so it would be in a more closed position at rest?
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68 GTO,3860# Stock Original 400/M-20 Muncie,3.55’s 13.86 @ 100 Old combo: 462 10.75 CR,,SD 330CFM Round Port E's,Old Faithful cam,Jim Hand Continental,3.42's. 1968 Pontiac GTO : 11.114 @ 120.130 MPH New combo: 517 MR-1,10.8 CR,SD 350CFM E's,QFT 950/Northwind,246/252 HR,9.5” 4000 stall,3.42's 636HP/654TQ 1.452 10.603 @ 125.09 http://www.dragtimes.com/Pontiac-GTO...lip-31594.html |
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#6
12-01-2005, 12:58 PM
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With the AFB the primary jets are larger than the secondary (even tho the secondary is larger) because of the metering rods. Remember that the effective metering of the primary jet is the area of the jet less the dynamic area of the rod at that point in time.
Modifying the airvalves NORMALLY obtains less than desirable results. Pontiac AFB's are not uncommon at the swap meets and not overly expensive. Besides, you may wish to change the rods as well. Jon.
__________________
"Good carburetion is fuelish hot air". "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
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#7
12-01-2005, 11:06 PM
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Try it as is and test from that baseline. I try to get my primary side dialed in first by removing the secondary link. I like to use the metering rod springs kit from Edelbrock Choose the springs rated to approx 1/2 your idle vacuum (in gear if an automatic). Edelbrock jets and rods will work if you cant get the "Carter" jets. edelbrockoffers a wide range of metering rods/ jets. Advance auto is cheaper but they dont and wont order any that arent in the warehouse. Auto Zone seems to get them overnite most times but cost more. pep boys can get them too. Carbking (and others) can get you parts too and good Pontiac specific advise. I found some notes from my brothers 65 GTO back in 1970 "P4B Edelbrock hi-rise new 625 carter metering rods from stock carb 392 jets front and rear best to date" no mention of other combos tried or actual results. . Dont know if it was a 4759 carb but the calibration seems reasonable.
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