High Altitude tuning

[DocMel]

Please keep this post to engine timing only:  No carb, cam or head recommendations

I have a 1968 440.  I live at 8000 feet ASL

I have my timing at almost 20 dgrees BTC, and thats about the best results I have at this point

Please share your high altitude timing results, what altitude you set timing at

Thanks

[femtnmax]

Work truck is 67 410.   Live at 5000 feet ASL.  Timing set at 10 deg BTC.  If I advance 2 deg further starter struggles to turn engine over.  Total advance is 34 degrees.

[Aussie Challenger]

I think the max advance should not alter no matter how high you are up the mountain, over advancing at static will over advance the max unless you shave the total advance back to compensate.
I know you don't want carb talk but air/fuel mixtures need to be adjusted the higher you go.

[HP2]

Gotta say, I've never actually measured it.  I just advance it until it gets the highest idle and still turns over smooth. I then tweak it with vacuum disconnected, under load, and back it down until any pinging disappears. After that you need to get the max vacuum advance under cruise. Again a slight tweaking method of the canister until I find the pinging threshold, then I back it off a bit.

[djwhog]

Definetly more bas timing needed, I am at close to 6k, air is thin, thinner yet for you, air/fuel and timing make a diff since less O2 in the mix and thus less to burn, so it does seem to make up some for the loss of good air when in high country.

Overall though, you still need to limit the total, when you increase the base that much you generally still want 32-38 max in most all case on the mech side and all in at 2400-2800 depends on setup cam etc gears you get the picture.

I run even on my stock 340 70 cuda 15 base instead of 10 and it does not ping, knock etc on 92 gas and is much more responsive.

That is why modern have an advantage, knock sensors, map and baro sensors make all the needed adjustments with EFI, so you are on the correct path buddy:)

[Supercuda]

The basic guideline for timing is to increase timing from initial sea level spec by about 1.5 degrees per 1000ft of altitude increase. At 6000 ft, I used 14.5 degrees as the calculated baseline, and set it at an indicated 14 BTDC. Total timing also has to increase, so you should not have to modify the distributor from its "happy place" at sea level. Just move the entire curve by a few degrees, and call it good. My shiftfrom 10 BTDC sea level to 14 BTDC at 6000 ft was just right.