390 Timing
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390 Timing
I have a 390 which I seem to have trouble getting timed correctly. The motor was rebuilt about 4 years ago I am told...At a price tag of about $4100..not sure if I believe that but anyway..If I go by the marks on the harmonic balancer the engine runs rather nice until acceleration and I get pinging, I simply keep retarding the timing until no pinging at acceleration..Now the problem to me is that the motor seems sluggish once set for no ping, and the timing mark on the balancer is not even close to 12 degrees...not sure if I have a problem or not, but engine just seems to run better when the timing is advanced.., better idle.
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Joined: Apr 2004
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Do you know the compression ratio?
Stock 390 2vs, at least in cars, were 6 degrees. 4v, "Premium Fuel" required, were 12. Many here talk 8 and 10 degrees.
Normal to get a better idle with timing advanced. It's the loaded running that matters, so you are going to have it backed off a bit or buy the high-priced spread.
Stock 390 2vs, at least in cars, were 6 degrees. 4v, "Premium Fuel" required, were 12. Many here talk 8 and 10 degrees.
Normal to get a better idle with timing advanced. It's the loaded running that matters, so you are going to have it backed off a bit or buy the high-priced spread.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
Pull the #1 plug, rotate the engine until the piston is at top-dead-center, and check the marks on the harmonic balancer. There' s a good chance it "spun" and it no longer shows the correct timing.
Also, you could just have a really big cam. Too much cam, and it won't idle right without some major advance at idle.
You might need to recurve the distributor, adjust the vacuum advance, or disconnect the vacuum advance all together.
What gas are you running? Might need to be 93 octane.
Also, you could just have a really big cam. Too much cam, and it won't idle right without some major advance at idle.
You might need to recurve the distributor, adjust the vacuum advance, or disconnect the vacuum advance all together.
What gas are you running? Might need to be 93 octane.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Pull the #1 plug, rotate the engine until the piston is at top-dead-center, and check the marks on the harmonic balancer. There' s a good chance it "spun" and it no longer shows the correct timing.
Also, you could just have a really big cam. Too much cam, and it won't idle right without some major advance at idle.
You might need to recurve the distributor, adjust the vacuum advance, or disconnect the vacuum advance all together.
What gas are you running? Might need to be 93 octane.
Also, you could just have a really big cam. Too much cam, and it won't idle right without some major advance at idle.
You might need to recurve the distributor, adjust the vacuum advance, or disconnect the vacuum advance all together.
What gas are you running? Might need to be 93 octane.
Lead Driver
Joined: Aug 2003
Posts: 7,592
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From: **** hole San Jose ca.
Maybe your not doing it right. Idling down around or less 550-600. Remove Vac-advance line and plug it. Make sure you points our set first 0.17-. if it has the smog heads 0.21..if not a electronic pointless setup.
Then do your timing 8-10 for most, ran good depending elevation where you live..
Then do your timing 8-10 for most, ran good depending elevation where you live..
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Well everything is electronic ignition, distributor. Yes I had the vaccum line plugged and disconnected. Now I was having other problems with the truck recently not starting..the starter seemed weak and noisy so I replaced it with a new one and new starter cable from solenoid. A couple of days later truck would not start, boosted started drove for a while would not start. Preformed load check on truck alternator not functioning properly..changed alternator..drove would not start..Found connection on regulator to be the cause of no charge.. fixed. Good for a couple of days then no good. Check voltage at battery 12.8, voltage from battery to starter solenoid 1.8...replaced battery connection..voltage at starter solenoid 12.7 starts fine..Love troubleshooting and fixing learning alot.. now one question could the electrical problems cause pinging due to low voltage situation affecting electronic ignition and distributor..I will probably try to advance the timing again tommorrow, but just wondering if this could be causing some of my problem..
Also what does recurving the distributor involve..learning new things here it's great.
Also what does recurving the distributor involve..learning new things here it's great.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
hmm haven't not messed with fords electronic ignition or the box. I can't see where low voltage would cause it to ping, which could be a to lean or to much advance or to low of octane fuel. Maybe you have a carbon build up. If your vacuum advance is hooked up wrong it can make it ping also.If yours is the double pull type the side port comes off the intake vac. The end port comes off the carb vacuum. Yours may go through a coolant sensor on intake or water hose adaptor.. Aww Trouble shooting only makes you smarter and can take yrs to learn for some.. keep up the good work.. my 2cents
orich
orich
