5.0 EFI-- ignition timing?
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Freshman User
Joined: Jul 2004
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5.0 EFI-- ignition timing?
Recently rebuilt my 1989 302. Bored .030 over, new comp cam XE250H-14. Runs good now, but I had to bump the timing way up from what the books call for. Book says set base timing (with SPOUT connector out) at 10 degrees advance. It ran real "doggy" at that setting. I now have it set on 18 degrees advance and its running great. There's no sign of detonation and its not running hot. My questions are why would I be so far off what the book says do and what kind of risk am I running advancing it 8 degrees over spec?
I know the computor uses the base timing as its reference point for making adjustments for conditions, so are there certain conditions that will put me out of the "safe" range for timing with 18 degrees advance base timing?
I know the computor uses the base timing as its reference point for making adjustments for conditions, so are there certain conditions that will put me out of the "safe" range for timing with 18 degrees advance base timing?
More Turbo
Joined: Jun 2004
Posts: 690
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From: Sweden
There should be some bad consequences. The computer takes over once you get the engine started, I don't think it even cares what the base timing is for most of its operation as long as it's within the range the dizzy's ignition module will allow it to be varied off of base.
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That's what I thought too, but it wouldn't run worth a flip at 10 BTDC. It had all the symptoms of retarded timing. But she run's great at 18 BTDC! Starts easy, not running hot, great throttle response, and no detonation. Could it be that my balancer has slipped. I've heard of this. Maybe my timing is actually closer to 10 BTDC in reality, but shows as 18 due to slipped balancer?
Junior User
Joined: Nov 2004
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i have messed with several 5.0 stangs over the years and even with the stock h.o. i could run anywhere from 12-14 degrees on the timing and the stock motor ran really good! best way to figure out what the best for you is go 2 degrees up in timing at a time till' it starts to ping on you,the move back 2 degrees should get ya close to where you want to be! hope this helps!
Lead Driver
Joined: Nov 2002
Posts: 9,558
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From: Concord, NC
The timing marks on the damper could be off from TDC, and the reading of 18 degrees is a false reading. You can check that if you like, or if the engine runs well and isn't pinging, leave the timing where it is. It does matter what the base timing is - the computer advances from that point because all the timing signals to the computer come from the distributor. There is no other reference point for the computer, so setting the base timing correctly is important to how the vehicle runs (the computer can't retard the timing if the base timing is set too high). I have always advanced the timing until I hear pinging, then pulled it back a degree or so from there.
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