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Help with secondary jetting


Well-Known Member
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12:20 AM
Mar 9, 2019
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I need some advice on what to put in the secondaries. This is a cruise car I did for my Dad, just a 1 day a week driver. So far the car is near perfect with the exception of being pig-rich once you get into the secondaries.
Here are the details:
383, +.040, TRW flattops, .038 quench. 915 1.74 heads, bowls and ports lightly cleaned up. Cranking compression 170psi. Comp Thumper (the smallest one) HP manifolds, 2.5” TTI. Chrysler iron 343hp intake with 2 650cfm AVS2’s. Timing is 24° initial, 36°, runs great/ no ping with 93 Sunoco that we have in our area. 727, Hughes 2500, 3:55/grip and 27" tires. The carbs are 1:1 linkage and I’ve leaned the primary power and cruise 2-ish stages with dot #18 from the chart for the 1905 carbs. I also lightened up the springs to yellows and am using the slowest pump shots. This whole setup works and runs very well except once you go past 1/2 pedal it dumps way too much fuel. (Black smoke, almost stalls)
Stock is .098’s. I was thinking of trying .080’s. Does anyone have any input? Buying 4 of them at a time is $30 bucks so I don’t want to keep throws jets at it blindly. And again this is a cruise car, I’m not tuning for perfection I just got to get it more in the ballpark. (And I know duel 500’s would have been a way better choice but I already had one of the 650’s.
Here’s a short Vid if you are curious, the exhaust dumps are open in the vid, my Dad gets his kicks from those.

Thanks for any input!
Buy small jets to try. If not what you desire, drill them larger-until you are happy. They can also be shrunk with solder!
Try tightening up the secondary air valve, sounds like it may be opening to much to soon. That seems like alot of Carb for that 383. My 2x4 383 has 2 500 performers and I had to lean the secondarys from 95s to 77s really cleaned it up. I hear you on the cost tuning a 2x4. Try the air valve adj it is free and you can always go back. Just think about 4 98s all at the same time, that is alot of fuel. I got much info from Eddy, they have a 2x4 for a SB Chevy and they did the same lean out and also on the primary side with a rod change from 65x52 to a 65x57 with a 86 jet. I did the rod change but went with 83s. With the original carb set up plugs would carbon foul quick now they are a nice whitish/ tan. Try some 77s see how it likes it and maybe drill to 80 max as it changes the flow of the jet and is not reccomended by Eddy. Well they want to sell you more jets ya no.
When the engine has 8 t/bores to draw on, the signal [ vacuum ]to each bore is reduced compared to a single 4bbl. So does not necessarily mean stock jetting is too rich.
I suspect the air valves are too tight. Less 'pull' on them, so acting like a choke & causing a rich mixture. I would leave the jets & back off the AV spring tension.