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I'm in the middle of rebuilding my 4bl carb on my '64. I took LOTS of pictures as I disassembled it, but did not realize that there are two different size jets that feed the primaries vs the secondaries of the carb. My carb is an oddball Holley 4360 that may not be familiar to many, but I'm guessing that my question is pretty much the same for all 4bl carbs:
Do the larger jets feed the secondaries in the carb and the smaller jets feed the primaries, or is it the other way around?
You are correct - deleted the post....
I was confusing the numbers on the jets with diameters....
For instance - for 63 the WCFB has 120-165 front jets and 120-220 rear jets (it may be 222 - I'm working from memory here)
Senior moment....
Last edited by Frankie the Fink; 07-07-2018 at 04:50 PM.
There are 7 4360 carbs in one area of that list. All have either N/S or N/A across the board for jets, etc. I learned that the Economaster (4360) uses metric threaded jets, and Weber jets will work. 4160 carbs have unique numbers.
Last edited by 65tripleblack; 07-08-2018 at 09:02 AM.
I'm new to the forum and new to Corvettes. Just bought my first 'vette 3 days ago; a '56 with dual quads. It's beautiful!! I'll try to attach a pic. It is in really good shape and runs good except it's running WAY rich. I can see it and smell it. It has a 2626S in front and a 2627S in the rear. Any quick, easy things to try? I'd like to enjoy it for a bit before I start ripping into it. I'm not intimidated by rebuilding the carbs if that's what it takes, but I have zero experience with dual carbs adjustments. Do the air mixture screws have any affect other than at idle? Any advice/suggestions would be greatly appreciated. Thank you,
NIck
Hi Nick and welcome to the forum! Beautiful car, looks like my 57’s twin
My car ran pig-rich when I first put the dual wcfbs on it, but previous owner had WAY oversized jets installed for racing. After installing proper sized jets, car ran great. Also check to be sure your choke is operating as it should, and your needle & seats are closing, floats aren’t sticking and allowing fuel to dribble down into the venturis at idle - I had this problem with mine. Good luck!
I'm new to the forum and new to Corvettes. Just bought my first 'vette 3 days ago; a '56 with dual quads. It's beautiful!! I'll try to attach a pic. It is in really good shape and runs good except it's running WAY rich. I can see it and smell it. It has a 2626S in front and a 2627S in the rear. Any quick, easy things to try? I'd like to enjoy it for a bit before I start ripping into it. I'm not intimidated by rebuilding the carbs if that's what it takes, but I have zero experience with dual carbs adjustments. Do the air mixture screws have any affect other than at idle? Any advice/suggestions would be greatly appreciated. Thank you,
Nick
Originally Posted by vettepoor
Hi Nick and welcome to the forum! Beautiful car, looks like my 57’s twin
My car ran pig-rich when I first put the dual wcfbs on it, but previous owner had WAY oversized jets
Originally Posted by ghostrider20
Stock Holley 2818 used on the 350/365 SHP cars used #65 in the front and #76 in the back.
Mark
First thing, great-looking '57 there.
But, just how does one go about installing the correct jets for a car? I'm reassembling a '65 327/L76 (365HP) but it will not be purely stock - pocket ported heads with most likely an LT1 cam. The carb is an over the counter 2818, correct for the L76, but a 1972 date stamp. So, just how does one go about correctly jetting these things? FWIW, the '66 Corvette engine that came in it had a Rochester 4-jet carb (never ever used on a Vette) and was grossly over-rich.
But, just how does one go about installing the correct jets for a car? I'm reassembling a '65 327/L76 (365HP) but it will not be purely stock - pocket ported heads with most likely an LT1 cam. The carb is an over the counter 2818, correct for the L76, but a 1972 date stamp. So, just how does one go about correctly jetting these things? FWIW, the '66 Corvette engine that came in it had a Rochester 4-jet carb (never ever used on a Vette) and was grossly over-rich.
The 2818 was originally equipped with #64 pri and #74 sec main jets, and used a # 6.5 power enrichment valve. You should not have to re-jet your carb if you are only doing the mods that you indicate.
I like to test the primary jets for proper mixture by getting engine hot, then taking a cruise at a STEADY (minimum to no operation of accel pump by varying throttle position) 65-75 MPH. This gives the plugs time to burn off excess fuel and to stabilize. Cruise is when the engine runs at its leanest. After about 5 10 minutes of steady speed, put in the clutch, shut off the engine and coast to a safe place to stop...................like a rest area, etc. Either let it cool somewhat or wear gloves and remove ALL 8 spark plugs. Check for color of the insulator. They should all be light tan or light gray. Take pictures of numbered plugs and post here for our perusal.
Secondary side is tougher and use of a dyno, air/fuel meter, or trap speed at the drag strip to determine best power. WOT A/F ratio usually drops to around 12:1 at low speed and slowly climbs to around 14:1 at redline. Ideal WOT ratio is between 12.5 - 13:1 for moderate duration cams. WOT mixture variation can be adjusted by varying the high speed air bleeds on both the pri and sec side. If the jet size is grossly rich, you'll see a puff of black smoke when you tip into the throttle. If grossly lean it will stumble at tip in.
FYI: 1970-72 LT1 with 750 cfm Holley used 70 pri and 80 sec jets.
Last edited by 65tripleblack; 07-14-2018 at 11:09 AM.
07-07-2018, 02:50 PM
Which size jets feed Primary vs Secondary
