Carb problem
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Junior User
Joined: Jan 2000
Posts: 78
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Carb problem
I have a 390 with a list of mods. I have ran it fine with a 600 cfm edelbrock carb for some time now. Recently,when you floor it,its lost alot of power. I replaced the fuel pump and still no help. I changed the rod that makes the secondaries open so it would barely open when its floored. It runs plenty strong there but i dont know why it just started doing this. Theres no black smoke so Im assuming that its not getting enough gas when the secondaries open. What else should i check? And why would it just start doing this like overnight?Thanks for any replies
Elder User
Joined: Oct 1999
Posts: 917
Likes: 3
From: Kelseyville USA
Carb problem
There are 2 small pistons that hold the metering rods in the primary jets. Under the pistons there are springs (one under each piston) Just Maby the springs have broken or the pistons are gummed up.. The springs `LIFT the metering rods UP under low vacuum conditions like full throtle...
This ADDS more fuel to the incoming air volume as the throttle is opened.... BUT the metering rods will stay down IF there is a problem
There is a small screw that holds the cover on over the pistons (1/4" socket type). Do Not take the screw all the way out Just loosen it enough to slide the cover around and the piston and metering rod will `POP UP`... check for smoth operation.. DO NOT FORCE the meetering rod back down... Just wiggle it and it will go back down into the hole in the jet.. slide the cover closed and GENTLY tighten the screw...
__JOHN__Õ¿ö
72 F-250
http://clubs.excite.com/comm/area/pw/welcome/main.asp?cid=188005&auth=
This ADDS more fuel to the incoming air volume as the throttle is opened.... BUT the metering rods will stay down IF there is a problem
There is a small screw that holds the cover on over the pistons (1/4" socket type). Do Not take the screw all the way out Just loosen it enough to slide the cover around and the piston and metering rod will `POP UP`... check for smoth operation.. DO NOT FORCE the meetering rod back down... Just wiggle it and it will go back down into the hole in the jet.. slide the cover closed and GENTLY tighten the screw...
__JOHN__Õ¿ö
72 F-250
http://clubs.excite.com/comm/area/pw/welcome/main.asp?cid=188005&auth=
Elder User
Joined: Oct 1999
Posts: 917
Likes: 3
From: Kelseyville USA
Carb problem
Could there be a relationship between the Ignition problem in the other forum and the Carb thing here???
Iam just thinking its not a carb thing maby timing! or just the ignition going away like its time for a Tune Up...
__JOHN__Õ¿ö
72 F-250
http://clubs.excite.com/comm/area/pw/welcome/main.asp?cid=188005&auth=
Iam just thinking its not a carb thing maby timing! or just the ignition going away like its time for a Tune Up...
__JOHN__Õ¿ö
72 F-250
http://clubs.excite.com/comm/area/pw/welcome/main.asp?cid=188005&auth=
Thread Starter
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Junior User
Joined: Jan 2000
Posts: 78
Likes: 0
Carb problem
No, it was doing it before I started the pertronix conversion. Everything is new,distributor,timing chain,everything in the ignition system. Even new fuel pump. Only thing it could be is carb. I reset the thing that opens the secondaries so that they barly open and it runs pretty strong there, but I dont know why it changed. It used to wrong strong with the secondaries all the way open. I dont know what else to do.
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