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Author Topic:   ignition timing
dode
Dirt Freak

Total posts: 417
posted May 23, 2002 03:14 PM UIN: 13209501
ok...after hearing every possible answer, I will come here in search of advice. My question is on our factory stock (basically stock 350 with a cam running 91 octane), I am searching for an answer as to what to do with the vacuum advance. I have had people tell me to take it off, and run enough base timing to give me about 36 degrees of total timing (will it even start like this? I have tried running more timing before, and it wouldn't start). I have had people tell me to hold the vacuum advance all the way advanced, which is basically the same as the first option I think, and I have had people tell me to just run the vacuum advance. What should I do? I checked the timing with my advance timing light last night, and we are reaching 32 degrees of timing by 3000 rpm with the vacuum advance hooked up. I did not take it any farther since it was close to midnight. I know things are working right in that respect, so what should I do? Thanks.

John

dirtbuster
Dirt Freak

Total posts: 353
posted May 23, 2002 04:32 PM
I would forget the vacuum advance all together and just use the mechanical advacne built into the distributor. The vacuum advance only works at part throttle anyway so at wide open it doesn't do anything plus it is one more thing to cause problems if it doesn;t work right.

Just rev the motor up and set total timing at 36 or what ever you want and then let it fall back at idle. If it is a stock hei then you will probably end up around 15 degrees at idle. you should have no problem getting it started there but if you do then you can buy advacne curve kits that would change the amount of advance so that you could have 36 total and around 10 or so at idle.



dode
Dirt Freak

Total posts: 417
posted May 23, 2002 04:36 PM UIN: 13209501
say on a standard HEI distributor, where should I get all the possible mechanical advance? At what rpm?

John

dirtbuster
Dirt Freak

Total posts: 353
posted May 23, 2002 05:43 PM
If you have the stock weights and springs i think it should all be in by 4000 maybe a little less but I'm not sure. Try revving it to 3500 and watch the timing mark then rap the throttle if you see the mark move then there is still more advance to come in yet.

If you get a curve kit most of them have a chart that will tell you how much advance and at what rpms with a given weight/spring combo.

[This message has been edited by dirtbuster (edited May 23, 2002).]

racer17j
Dirt Forum Champ
Total posts: 1565
posted May 24, 2002 02:21 AM UIN: 54865418
you can get the block off plate for your hei at the local gm dealership they came on dump trucks i belive and get a advance curve kit. if you have problems starting like i did last year went thru 6 flywheels and starters and never even hit the track i read on a earlier post about spinning the motor over and then hitting the switch to the hei so i thought i'd give it a try and sure enough i tried to start with the power on and it lugged like a big dog then i killed the switch and hit the starter again and she took right off when i turned the power switch on

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