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73-87 Chevy _ GMC Trucks => Performance => Topic started by: klaussk on March 30, 2011, 03:21:04 pm

Title: timing advance
Post by: klaussk on March 30, 2011, 03:21:04 pm: just curious if anyone has advanced there timing to run premium fuel. if so let me know what kind of advance you are running
Title: Re: timing advance
Post by: Da67goatman on March 30, 2011, 06:36:49 pm: Who can afford premium? You only need premium when you get to some serious compressions.
Title: Re: timing advance
Post by: 1980c10 on March 30, 2011, 09:46:27 pm: 32 degrees advanced
9.7:1 CR
vacuum advance hooked up
87 octane
no pinging
Title: Re: timing advance
Post by: 1979C20 on March 30, 2011, 11:16:34 pm: How did you get 32? The timing tab only says to 10 or 12?....
Title: Re: timing advance
Post by: Grim 82 on March 30, 2011, 11:22:56 pm: Dial back timing light. He's referring to total advance.
Title: Re: timing advance
Post by: klaussk on April 05, 2011, 06:50:46 pm: I found out that the timing tab on my truck is missing. And my dad Used to run mallory ingnitions on all his trucks when he was younger and he said he would advance timing and see a major improvment. I failed to mention this before but I have a 305. Don't they have a fair amount of compression already.
Title: Re: timing advance
Post by: Grim 82 on April 05, 2011, 09:51:26 pm: Quote from: klaussk on April 05, 2011, 06:50:46 pm
Don't they have a fair amount of compression already.
Not really high compression like Da67goatman mentioned. There are so many variables, and we don't know much else about your motor other than it is a 305. There are many aspects to ignition timing, and yes you can tweak it from the stock setting to make more power and mpg, but if your motor is stock, there isn't much that you can do to "tune it to run on premium fuel" that's any different to just "running on regular fuel". When you build a motor and the sky is the limit you can tune it down to run on pump gas, because the comp ratio can be controlled by the components that you use. When the motor is already in and designed to run on mid or low grade fuel, it is what it is. You should advance your timing more than the stock spec, probably around 10 to 12 degrees base timing, as opposed to 8, 6, or 4. You can advance your timing enough that it performs worse. If you advance it and make better power on 87 octane, but it pings, run 89, or......
Again with the variables, if you have electronic spark control, get rid of it. There are lots of ways to reduce spark knock besides using higher octane fuel, which include lowering the combustion temp with a lower temp t-stat, running the EGR valve, hooking to full manifold vacuum for your vacuum advance, recurving your distributor, or even richening your fuel mixture. A lean condition will make pinging more evident.
Title: Re: timing advance
Post by: 78 Chevyrado on April 06, 2011, 10:43:05 pm: Mines supposed to be set at 8 degrees-initial but I run it at about 12 to 13 degrees initial on 87 octane with no problems. made quite a difference.
Title: Re: timing advance
Post by: klaussk on April 10, 2011, 09:40:57 am: thanks guys. I ended up taking my truck to a shop. Im pretty sure its having electrical issues with the ignition system because it will just lose spark mostly after you get the engine warmed up.But I did have it running just fine. I can never trace down electrical issues. I just have no idea what Im doing when i look at electrical stuff. So Im just having the guys at the shop time it and tune the carb for me. I feel like they will do a much better job at timing than I will by ear.