How much timing can you get away with at high altitude?
09-13-2013, 10:54 AM
#1
Le Mans Master
Thread Starter
How much timing can you get away with at high altitude?
I've been playing with my timing lately and so far have found that 20* initial 36* all in and 54* total is liked by the engine.
I have absolutely no ping at any time with these settings. Crisp off idle response and good response throughout the rpm range.
My car lives between 4000 and 8000 feet depending on the temperature.
I modified my mechanical to limit to 16* for my all in of 36* but thinking I could go more on the mechanical advance, maybe 18* for an 38* all in and then pull back some of the vacuum timing for cruise. Also right now the timing is fully advanced by 2350 rpm. I found I could bring that in much sooner too for better performance and still no ping.
so I'm curious how much timing other people at high altitudes have been able to get without ping?
My CR is 9.9:1 on a mild 350 with a 270 cam and 54* of overlap, a 2500 stall converter (observed) a th350 and a 3.08 rear end. I'm a little surprised with this combo that I can get this much advance and not run into trouble.
The extra timing at idle really smooths it out and it can idle at 600 rpm if I want it to.
I have absolutely no ping at any time with these settings. Crisp off idle response and good response throughout the rpm range.
My car lives between 4000 and 8000 feet depending on the temperature.
I modified my mechanical to limit to 16* for my all in of 36* but thinking I could go more on the mechanical advance, maybe 18* for an 38* all in and then pull back some of the vacuum timing for cruise. Also right now the timing is fully advanced by 2350 rpm. I found I could bring that in much sooner too for better performance and still no ping.
so I'm curious how much timing other people at high altitudes have been able to get without ping?
My CR is 9.9:1 on a mild 350 with a 270 cam and 54* of overlap, a 2500 stall converter (observed) a th350 and a 3.08 rear end. I'm a little surprised with this combo that I can get this much advance and not run into trouble.
The extra timing at idle really smooths it out and it can idle at 600 rpm if I want it to.
Last edited by REELAV8R; 09-13-2013 at 10:57 AM.
09-13-2013, 02:35 PM
#3
This is from a not current version of one of Lar's papers, sounds like 38 is the limit.
The 36-degree 2500 rpm advance curve is optimum for performance, but may require premium fuel. Lug
the car around, and punch the throttle at low rpm while listening for detonation (“engine knock”). If you’re
getting any audible knock, you MUST retard the timing. Retard the timing in 2-degree increments until
engine knock stops. Engine knock will seriously damage engine components if not corrected. If you get
no knock, you may see slightly improved performance at 38 degrees total timing. This is particularly true
if you’re running at high altitude.
The 36-degree 2500 rpm advance curve is optimum for performance, but may require premium fuel. Lug
the car around, and punch the throttle at low rpm while listening for detonation (“engine knock”). If you’re
getting any audible knock, you MUST retard the timing. Retard the timing in 2-degree increments until
engine knock stops. Engine knock will seriously damage engine components if not corrected. If you get
no knock, you may see slightly improved performance at 38 degrees total timing. This is particularly true
if you’re running at high altitude.
09-13-2013, 03:55 PM
#4
Le Mans Master
Thread Starter
The 36-degree 2500 rpm advance curve is optimum for performance, but may require premium fuel. Lug
the car around, and punch the throttle at low rpm while listening for detonation (“engine knock”). If you’re
getting any audible knock, you MUST retard the timing. Retard the timing in 2-degree increments until
engine knock stops. Engine knock will seriously damage engine components if not corrected. If you get
no knock, you may see slightly improved performance at 38 degrees total timing. This is particularly true
if you’re running at high altitude.
the car around, and punch the throttle at low rpm while listening for detonation (“engine knock”). If you’re
getting any audible knock, you MUST retard the timing. Retard the timing in 2-degree increments until
engine knock stops. Engine knock will seriously damage engine components if not corrected. If you get
no knock, you may see slightly improved performance at 38 degrees total timing. This is particularly true
if you’re running at high altitude.
What I'm finding is that even with my tall gearing and poor 1st gear ratio it still does not ping. Even full throttle acceleration in 3rd right after the shift from 2nd which my stock engine would give me ping does not cause this engine to ping.
Just curious what others have found in their experience and what CR and gearing was being used.