Timing Advance: How Much Can I Get Away With?

[Stinger]

I picked up an adjustable timing plate and I need to know what I can probably get away with a still run pump gas.

 

I've Milled the stock head to 21cc which gets me 150psi compression. Premium fuel here is 91 octane. I'm at 1600ft elevation.

 

I'm wanting to try +4 but I don't know if I can get away with that much advance. I'm afraid I won't be able to "hear" detonation if it's too much and I'll have a meltdown. I can here detonation in my Turbo Mustang but it's not screaming loud like the Shee..

 

Is +4 too much?

[wayfst]

+4 or +5 you should be ok. higher than that you'll need race fuel. watch your plugs, if they turn yellow turn it back down.

[Wallrat]

Uh I'm not so sure on that one. I'd try +2 if it were my bike since its f'n hard to hear detonation on a shee.

[FIRST BANSHEE]

I'm running +5, 155 psi on 92, no problems so far.

[bigboybanshee]

I was running +4 timing, 155psi, @ sea level on 93 octane...no problems at all

[bogart]

why not just get 93 oct.

[JArmShee]

In some places 91 is the highest rated octane. I know here on LI NY 93 is premium.

[Stinger]

why not just get 93 oct.

365015[/snapback]

 

It's not available here...87 is regular, 89-90 is midgrade, 91 is premium.

[Ducman]

I think 150 psi and +4 will be fine at 1500+ elev on 91 oct. Make sure you aren't lean on your jetting.

[gurny]

I run 170psi 93 oct with a +4. I m fine just don tforget to check jetting just incase.

[cbn70]

once you advance you timing, do you need to rejet??

[05bansh]

once you advance you timing, do you need to rejet??

365410[/snapback]

Not if your jetting is dialed in. Just double check it to be safe. You only need to re jet when you are running more air through the engine like, pipes, reeds, filters....