Ignition Timing
June 20th, 2012, 05:18 PM
#1
Registered User
Thread Starter
Join Date: Feb 2009
Location: New Jersey
Posts: 229
Ignition Timing
Hey All,
Quick question, from the specs I have, factory timing for my stock 68 4bbl eng is 7.5 degrees. How much can I go on stock set up(points) with premium fuel? I am at 9.5 degrees now and no pinging but it still feels sluggish. New points, condenser, plugs, wires and cap/rotor. Only change: went from factory single exhaust to factory dual exhaust. From what I could find folks are talking 12-15 degrees? Seems high though.
Thanks, Joe
Quick question, from the specs I have, factory timing for my stock 68 4bbl eng is 7.5 degrees. How much can I go on stock set up(points) with premium fuel? I am at 9.5 degrees now and no pinging but it still feels sluggish. New points, condenser, plugs, wires and cap/rotor. Only change: went from factory single exhaust to factory dual exhaust. From what I could find folks are talking 12-15 degrees? Seems high though.
Thanks, Joe
June 20th, 2012, 10:32 PM
#4
Registered User
Join Date: Aug 2011
Location: Northlake, IL
Posts: 633
If you're not going to recurve or do anything else, you can go as high with initial as you'd like, provided you keep max (at 3,000+ RPM) at or below around 35. My initial is set to 15 degrees. Make sure you check your centrifugal weights to see that they're not binding, and also check your vacuum advance to make sure the canister isn't bad.
June 21st, 2012, 04:14 AM
#5
Registered User
Join Date: Jun 2010
Location: Rogues Island, USA
Posts: 3,613
I used a simple method to determine initial timing. But I also had an adjustable distributor that allowed me to put my total timing where I needed it.
I would bump up the initial two degrees at a time until it becomes hard to start. Then I'd go back two degrees and leave it. I'd then adjust the distributor to give me 34-36 total timing by 3000 rpm. As I stated this is much easier with a totally adjustable distributor but you can still get close with your set up.
By using the numbers off the distributor you can find out how much advance is 'built in' to it and work backwards from there. Those numbers are readily available on line.
My 330 is also factory set at 7.5 initial but I probably have 10-12 in it (been awhile and I forget) and with the high compression I can still use 91-93 octane with no problems.
I would bump up the initial two degrees at a time until it becomes hard to start. Then I'd go back two degrees and leave it. I'd then adjust the distributor to give me 34-36 total timing by 3000 rpm. As I stated this is much easier with a totally adjustable distributor but you can still get close with your set up.
By using the numbers off the distributor you can find out how much advance is 'built in' to it and work backwards from there. Those numbers are readily available on line.
My 330 is also factory set at 7.5 initial but I probably have 10-12 in it (been awhile and I forget) and with the high compression I can still use 91-93 octane with no problems.
June 21st, 2012, 04:48 AM
#6
Registered User
Join Date: Oct 2011
Location: Munich, Germany
Posts: 390
Don't know if it helps, but here's a link to a chart with Oldsmobile tune-up specifications...
http://www.tpocr.com/olds1.html
http://www.tpocr.com/olds1.html
June 21st, 2012, 06:53 AM
#7
Registered User
Join Date: Mar 2010
Posts: 372
7.5 initial is said to be the factory initial timing setting. however, i have learned it's better to set your full advance at 3000+ rpm, and let the inital fall where it falls. it usually ends up being some where in the 10-14 range initial this way. i just got mine where it needs to be, and the motor will tell you where it needs to be when you take it for a ride, lol. my 330 is at 12 initial, 34 all in at around 3200rpm. i use vacuum advance HEI....
June 21st, 2012, 08:33 AM
#8
Registered User
Thread Starter
Join Date: Feb 2009
Location: New Jersey
Posts: 229
If you're not going to recurve or do anything else, you can go as high with initial as you'd like, provided you keep max (at 3,000+ RPM) at or below around 35. My initial is set to 15 degrees. Make sure you check your centrifugal weights to see that they're not binding, and also check your vacuum advance to make sure the canister isn't bad.
I used a simple method to determine initial timing. But I also had an adjustable distributor that allowed me to put my total timing where I needed it.
I would bump up the initial two degrees at a time until it becomes hard to start. Then I'd go back two degrees and leave it. I'd then adjust the distributor to give me 34-36 total timing by 3000 rpm. As I stated this is much easier with a totally adjustable distributor but you can still get close with your set up.
By using the numbers off the distributor you can find out how much advance is 'built in' to it and work backwards from there. Those numbers are readily available on line.
My 330 is also factory set at 7.5 initial but I probably have 10-12 in it (been awhile and I forget) and with the high compression I can still use 91-93 octane with no problems.
I would bump up the initial two degrees at a time until it becomes hard to start. Then I'd go back two degrees and leave it. I'd then adjust the distributor to give me 34-36 total timing by 3000 rpm. As I stated this is much easier with a totally adjustable distributor but you can still get close with your set up.
By using the numbers off the distributor you can find out how much advance is 'built in' to it and work backwards from there. Those numbers are readily available on line.
My 330 is also factory set at 7.5 initial but I probably have 10-12 in it (been awhile and I forget) and with the high compression I can still use 91-93 octane with no problems.
Don't know if it helps, but here's a link to a chart with Oldsmobile tune-up specifications...
http://www.tpocr.com/olds1.html
http://www.tpocr.com/olds1.html
7.5 initial is said to be the factory initial timing setting. however, i have learned it's better to set your full advance at 3000+ rpm, and let the inital fall where it falls. it usually ends up being some where in the 10-14 range initial this way. i just got mine where it needs to be, and the motor will tell you where it needs to be when you take it for a ride, lol. my 330 is at 12 initial, 34 all in at around 3200rpm. i use vacuum advance HEI....
June 21st, 2012, 10:15 AM
#9
Administrator
Join Date: Oct 2009
Location: Poteau, Ok
Posts: 40,728
Plug the hose on your vacuum advance and set your timing to 34-36* BTDC @ 32-3400 rpm and then see where your initial winds up. You may need to get an adjustable vac cannister to fine tune your vacuum advance if its surging or pinging when your running at light load.
June 21st, 2012, 10:22 AM
#10
Registered User
Join Date: Aug 2011
Location: Northlake, IL
Posts: 633
I just got my timing dialed in properly and it made a HUGE difference. I was only getting 25 degrees total (initial+centrifugal) because I can't go beyond 15 degrees initial and my weights were only providing 10 degrees. When I finally recurved the distributor to provide 20 degrees centrifugal, it really woke things up. The only problem if you're pushing the limits here is that you need to check how much vacuum advance you're getting, and limit it to around 10 degrees if necessary. Otherwise you could run into situations where you are getting too much centrifugal and vacuum advance at the same time. I made a little aluminum restrictor plate to do this, very easy, it just stops the vacuum advance rod from going any further. By the way, I'm running 2.41 gears currently. At 25 degrees total advance, the motor hated the gears. At 35 degrees, it doesn't care in the least.
June 25th, 2012, 10:59 AM
#12
Registered User
Thread Starter
Join Date: Feb 2009
Location: New Jersey
Posts: 229
I moved the timing up to about 10-10.5 degrees, total timing at 3k to 3.2K is 36 degrees. No pinging and noticed a little difference maybe. I might push up to 12 degrees and see what happens. If it starts pinging, I'll drop it back. Pushing the 245-60-15's with limited slip 2.78 gears may be asking a lot.
June 25th, 2012, 12:39 PM
#14
Administrator
Join Date: Oct 2009
Location: Poteau, Ok
Posts: 40,728
I moved the timing up to about 10-10.5 degrees, total timing at 3k to 3.2K is 36 degrees. No pinging and noticed a little difference maybe. I might push up to 12 degrees and see what happens. If it starts pinging, I'll drop it back. Pushing the 245-60-15's with limited slip 2.78 gears may be asking a lot.
Thread
Thread Starter
Forum
Replies
Last Post
