454 timing

[Sdc77]

Hi eveybody,
I just rebuilt the carb, got new 8mm wires, and sparkplugs.

I would like to know what is the best timing for 90 AKI gasoline ?

It's 5° BTDC on the manual, my setup is also 6° BTDC, but I'm sure I can get more timing.

What is your guys setup ?

[Sdc77]

Ok, I find back the post already talking about it :

https://forum.supraboats.com/showthread.php?15432-fuel-consumption-vs-ignition-timing

I will go for 10° BTDC, maybe 12° and see what happens.

[wotan2525]

I always time by sound. Get it close with a light and then find the "sweet" spot between too advanced and too retarded at about 2500rpms while it is running.

[TitanTn]

Mine is happy at 10. I use both a light and sound. The light is just to make sure I'm in the right ballpark and then I agree with wotan - sound will tell you when you've hit the sweet spot.

[cadunkle]

AKI is ROM+MON/2? Just trying to figure what if your octane in France is measured same as in US (RON+MON/2). Here we have available 87, 89, 92, 93. I use 89 in my 454 Saltare and run 10* initial and 34* total. Might be able to get away with 87 but not sure. PO rebuilt my 454 and no idea what pistons he used or compression ratio, cam, etc. It runs well with this timing on 89 with no detonation so an extra $5/tank over 87 isn't worth worrying for me. Maybe if I'm bored one day I'll run it real low and try 87 but since my time on the water is limited and it's an hour tow I don't want to waste a day dealing with octane issues.

[Sdc77]

Hi cadunkle,
Thanks for your feedback.

Yes AKI is RON + MON /2. It's how you name fuel in the USA.

In France we have only 2 choices for gazoline, and we name it only with RON :

http://img.autoplus.fr/news/2013/12/30/1478542/636%7C424%7Ccbc431ecd2f16ed694969769.jpg

So our worst gazoline is SP 95 E10, means "Sans plomb, RON 95, 10% Ethanol", "sans plomb" = Unleaded.
On the low part of the fuel pump, we can read the RON and MON, but nobody is interrested in those things :

http://www.motorevue.com/article/article/d-apres-la-ffmc-la-majorite-des-motards-peinent-a-pouvoir-remplir-leur-reservoir--45329-1-v4zoom.jpg

a RON 95 is MON 85 = 90 AKI
a RON 98 is MON 88 = 93 AKI

So, with AKI 90, I will start like your setup with a 10° timing idle, and maybe try a little bit more, 11 to 12° and see what happen.

Thanks again ;)