holley 4160 mixture screws
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Elder User
Joined: Aug 2004
Posts: 620
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From: NE Wisconsin
holley 4160 mixture screws
Trying to dial in the 4160. Never delt with the reverse screws though. (ccw to lean) Why can't I kill the engine by leaning it out? How do these screws work?
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Joined: Dec 2001
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From: Louisville,Ky.
Perhaps the rear barrels are not closed far enough or the idle speed is too high and it is actually running off of the intermediate fuel circuit. also, verify that there is no fuel dripping from the boosters into the venturis from a high float level.
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Elder User
Joined: Aug 2004
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From: NE Wisconsin
Floats have been set and double checked. I can back off the idle screw until it no longer touches. Still idles. How could the rear barrels be open too far if their vacuum? Bent rod maybe?
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Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
There is a stopper screw under the carb. These usually don't get adjusted very often. To verify that this is not the problem, stuff a rag into the rear barrels and see if it still idles the same. If so, the the rears are ok.
The front jets may be too large. What is the list number of the carb and what engine is it on?
The front jets may be too large. What is the list number of the carb and what engine is it on?
Elder User
Joined: Nov 2003
Posts: 778
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From: southeast Idaho
Also check the fast idle cam on the choke to be sure it is not holding it open due to adjustment problems, and check your throttle linkage to be sure it is not too short and holding it open also, both are adjustable.. May need to use a light and look down the primaries to verify they are closing all the way..
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Elder User
Joined: Aug 2004
Posts: 620
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From: NE Wisconsin
Carb shouldn't be too small.
VE x cid x max rpms / 3456 = carb size
VE = Volumetric efficiency(how well the engine breaths) .75 to .80 = street
.80 to .85 = good street
.85 and above race
.85 x 405 x 4500 / 3456 = 448.2cfm
VE x cid x max rpms / 3456 = carb size
VE = Volumetric efficiency(how well the engine breaths) .75 to .80 = street
.80 to .85 = good street
.85 and above race
.85 x 405 x 4500 / 3456 = 448.2cfm
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Elder User
Joined: Aug 2004
Posts: 620
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From: NE Wisconsin
OK here's what I found out.
Took the throttle linkage off to eniminate that.
Made sure the high idle cam was not touching.
Threw a rag over the secondarys and the truck almost died. Must be suckin mixture on the secondarys and runing rich. I'll have to pull the carb. some other night to fix it.
Thanks LXman, never even thought about that screw to adjust the secondarys. I'll let ya know how it goes.
List 80452-1426
Took the throttle linkage off to eniminate that.
Made sure the high idle cam was not touching.
Threw a rag over the secondarys and the truck almost died. Must be suckin mixture on the secondarys and runing rich. I'll have to pull the carb. some other night to fix it.
Thanks LXman, never even thought about that screw to adjust the secondarys. I'll let ya know how it goes.
List 80452-1426
Senior User
Joined: Jan 2009
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If he has a 400 with the 4.0" bore and stroke. Adding .030 to the bore makes his engine a 408.
Carb CFM Calculator