390 Problems
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Senior User
Joined: Jun 2006
Posts: 198
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From: Vacaville, Ca
390 Problems
Hello all,I have a 1970 CS that came with a 360, I installed a 390 from a 68 F100 while it was out I installed the Crane Truck cam with new gears and chain,performer intake manifold with a Holly 570 cfm 4 barrel,changed the points to a pertronix kit and installed Dynomax headers into 2and 1/4" flowmasters.
Now the problem I'm having is getting the timing set,I'm trying to get it at 6deg adv but I have to keep moving the throttle to keep it running at that setting and sometimes it back fires thru the carb,also when I set it at say 10 or 12 deg adv.it will idle for about 20to 30 seconds then acts like it's starting to run out of gas,where if I rev it a few times will smooth out again for a short time,I have now increased the idle set screw so it will set there and idle at around 1300rpm and won't stall but when I try to put it in drive it stalls out unless I keep playing with the throttle,,, any thoughts,,Thanks for any help.
Now the problem I'm having is getting the timing set,I'm trying to get it at 6deg adv but I have to keep moving the throttle to keep it running at that setting and sometimes it back fires thru the carb,also when I set it at say 10 or 12 deg adv.it will idle for about 20to 30 seconds then acts like it's starting to run out of gas,where if I rev it a few times will smooth out again for a short time,I have now increased the idle set screw so it will set there and idle at around 1300rpm and won't stall but when I try to put it in drive it stalls out unless I keep playing with the throttle,,, any thoughts,,Thanks for any help.
Senior User
Joined: Dec 2000
Posts: 435
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From: Nebraska Farm
sounds to me like a fuel problem. check or replace the filter for starters. Is there junk in the gas tank that would be clogging you up? make sure the carb float is set. Also make sure all unused vacuum ports are plugged. but it sounds like you have plenty of vacuum.
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Senior User
Joined: Jun 2006
Posts: 198
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From: Vacaville, Ca
Well I'v been busy on other things but have figured out my problems. First off my distributer was bad,changed that out and I was able to set timing which stayed solid without jumping around. Second I changed the jets in the accelerator pump,new carb came with .034 I changed to .037 which took most of my problem away but have since changed to .039 jets. Third I changed my primary jets from .054's to .056's then settled on .059's. The only problem I have now is it's a real slug pulling from a stop with my timing set at 6 deg adv but if I set it at 10 deg pulls real nice
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Set the timing by total advance and forget the initial. Set total, no vacuum, to 36° at about 4000 rpm and then check initial. But 10° sounds more reasonable than 6°, at least from your discription of the situation.
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