390 Timing Questions
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Joined: Aug 2006
Posts: 18
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390 Timing Questions
Hi guys,
I just recently installed a brand new 600cfm Edelbrock carb and manifold onto my 390. What is the proper timing this thing should be set at? I was thinking around 10 degrees BTDC would be good. I've also heard that you should plug the vacuum advance when doing this. Well, I got my engine to idle decently, but when I stop it and plug the advance and start it again it runs really bad and backfires through the carb. It also ran the same way when I had the advance hooked up to the left side of the carb which is supposed to be timed advance for emission controlled engines. It is now on the right with constant manifold vacuum and it idles decently. I know I've got a lot of adjusting to do with my carb and maybe change the timing, but I'm wondering if anyone has experience with this or has any suggestions. Any help is appreciated.
Thanks,
Brian
I just recently installed a brand new 600cfm Edelbrock carb and manifold onto my 390. What is the proper timing this thing should be set at? I was thinking around 10 degrees BTDC would be good. I've also heard that you should plug the vacuum advance when doing this. Well, I got my engine to idle decently, but when I stop it and plug the advance and start it again it runs really bad and backfires through the carb. It also ran the same way when I had the advance hooked up to the left side of the carb which is supposed to be timed advance for emission controlled engines. It is now on the right with constant manifold vacuum and it idles decently. I know I've got a lot of adjusting to do with my carb and maybe change the timing, but I'm wondering if anyone has experience with this or has any suggestions. Any help is appreciated.
Thanks,
Brian
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
You need to put the vacuum source back where it belongs and adjust your carb till the engine idles properly without using the vacuum advance to correct the misadjustment of the carb. Rule of thumb, ported vacuum for a street motor and no vacuum advance at all for a race motor.
5th Wheeling
Joined: Jan 2005
Posts: 39
Likes: 0
From: Central NY
Youll probably have to advance the dist. a little more because by hooking to your manifold your advancing your timing at idle.You will have to use the ported vacuum outlet on the carb,its the one that wont have vacuum at idle but will when you rev it up,adjust your carb to get it close to normal then remove the hose from the v/advance and plug it then set your timing w the light start w 10 btdc and work on adjusting the carb again then retime again,etc
