Timing
Thread Starter
6th Gear
Joined: Apr 2019
Posts: 6
Likes: 0
From: Colorado
Timing
So I have a L36 390hp 427 and was wondering if anyone knows how altitude changes the timing or if it does were about 6000 feet above sea level and I’ve set my initial timing at 12 degrees advanced seems to be running good at lower rpm but at higher rpm seems to not be.
Carb is rebuilt and jetted for altitude it likely needs more fine tuning adjustment but I have to think timing with altitude needs maybe to advance more ?
any thoughts ?
Carb is rebuilt and jetted for altitude it likely needs more fine tuning adjustment but I have to think timing with altitude needs maybe to advance more ?
any thoughts ?
Le Mans Master
Joined: Aug 2005
Posts: 6,550
Likes: 1,983
From: Temple Terrace Florida
One of the gurus on timing on the forum is Lars. He lives in CO as well. Search for his papers on the forum. SWCDuke has also written a paper or two on the subject. There is a wealth of information right here. Jerry
Melting Slicks
Joined: Jul 2004
Posts: 2,870
Likes: 196
From: Maryland
My guess would be that you would need more lead due to the leaner air/ fuel mixture . The leaner the mix the more advance needed to burn .completely. 12* initial is pretty high for a big block.
Last edited by Donald #31176; Oct 19, 2019 at 04:19 PM.
Team Owner
Joined: Nov 2005
Posts: 28,262
Likes: 2,872
From: Beach & High Desert Southern California
The car needs more idle advance at altitude (and the test at 12 degrees confirms this), but it still need to limit the total advance to 36-38 degrees to avoid hitching and detonation at altitude. High altitude fuel is also blended to reduce vaporization compared to sea level fuel (much like Aviation fuel), a property that prevents vapor lock but also makes the fuel harder to ignite and burn clean with diluted air fuel mixtures. Lars distributor tuning papers can lead the way to a solution.
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,271
So I have a L36 390hp 427 and was wondering if anyone knows how altitude changes the timing or if it does were about 6000 feet above sea level and I’ve set my initial timing at 12 degrees advanced seems to be running good at lower rpm but at higher rpm seems to not be.
Carb is rebuilt and jetted for altitude it likely needs more fine tuning adjustment but I have to think timing with altitude needs maybe to advance more ?
any thoughts ?
Carb is rebuilt and jetted for altitude it likely needs more fine tuning adjustment but I have to think timing with altitude needs maybe to advance more ?
any thoughts ?
Duke
