Holley 600 Tuning Questions

[Mike Schwaderer]

I have a 66 289, just bought a new Holley 600 cfm Carb. 80457-3 Model.
The engine is new also, first time running this past weekend for 10 years.
Having trouble getting it to idle, it will run all day at about 1200-1500 rpm.
I trying to fine tune the carb, and it will die everytime I get close to normal idle speed. The primary jets in the carb are #64. Any suggestions, I did confirm the timing is @ 6BTDC. I do not hear any vacuum leaks everything is plugged.
Thanks Mike

 

[3spd on floor]

well first of all bump that timing up to at least 10-12*. The factory specs are rediculously low, as to be very safe. try that and see what problems it gives you. what, if any mods have been made to the engine?

 

[Stang_1973]

Any Mods you have will definately help.

 

[thehueypilot]

Well first off we need to know how radical your cam is. I have found that if your engine has lower vacuum because of a bigger cam the carb is a lot harder to get to idle. The main jets have nothing to do with idle quality. An easy trick to see if your idle is too rich is to gently put something like an ice pick into your idle air bleed on the primary side to see if the idle speeds up. If it does you need more air than fuel. One way to get more air is to slightly open your secondary throttle plates. Another method is to drill 1/8 inch hole into primary throttle plates but I do not recommend that method. The last method is to slightly enlarge the idle air bleeds. If you turn your idle mixture screws all the way in the engine should die. If it does not your transfer idle ports are uncovered so your engine is getting too much fuel and your primary throttle plates are too far open. Hope this helps!

 

[Mike Schwaderer]

Holley 600 Tuning

Well the engine is pretty much stock, Heads and Valve train also.
The cam and lifters are Comp cams 204/214 450/474 @ 0.50,Cloyes roller chain, HV Oil pump. It carrys 65lb of Oil pressure. Stock 4 bbl intake with the new carb. All items on the engine are new also all eletrical components and all Harnesses replaced as well. New distributor points set @ 0.16 Accel Tune-up kit with 8mm wires. I haven't mess with it this week looking for suggestions to work on this weekend. Does Holley make Primary jets smaller than .64??? My old 600 carb had .66s on the primary plate.
Thanks for any of the advice.

 

[thehueypilot]

Main jets do not effect idle quality. Jets range from #40 to #100. Make sure you have plugged all vacuum sources that are not in use. You might want to plug all vacuum ports to make sure you don't have a leaking vacuum advance or power brake booster. Start with your air/fuel mixture screws about one and a half turns out on both sides. Make sure float levels are correct. Is this a vacuum secondary carb? Is their a strong exhaust smell that makes your eyes burn? If so the idle is running too rich and needs more air added to the fuel. See my previous thread.

 

[ratio411]

Your combo is very mild, so you won't need any major mods to the carb. It should be real close 'box stock'.

Sounds to me like you are leaking vacuum somewhere, it's almost certain.

Like previously mentioned, bump up the timing, check any diaphrams for leaks, and make sure the float is not too high.

I am not sure about that model, but there is also a secondary idle adjustment on most Holleys... usually in conjunction with the choke linkage. Sometimes the 'fast idle' linkage can be sticky or adjusted wrong. When you get it idling, do you 'snap' the throttle to get the fast idle cam to release? If not, it can stay in that choke mode and idle high.

Before you do anything though, I will tell you as I tell anyone...
Get some books on tuning your model Holley carb!
You will be amazed how much you learn and how easy they really are if you just look at a book or two.
Good luck
Dave