timing

[sclafan1]

OK..I have a question shovelheads..I have a 76 FLH and the timeing needs be set. I have a two coil set up with dubble spark plugs (one on each side of the jug). I have a manuel and, a timming light so I familier with the timing mark on the fly wheel and how to set it....etc. Now with all that said...I have been told that when you have the st up that I explained (2 coils) the timming should should be slightly retarted. Can anyone give me any info???

[Rooster]

OK..I have a question shovelheads..I have a 76 FLH and the timeing needs be set. I have a two coil set up with dubble spark plugs (one on each side of the jug). I have a manuel and, a timming light so I familier with the timing mark on the fly wheel and how to set it....etc. Now with all that said...I have been told that when you have the st up that I explained (2 coils) the timming should should be slightly retarted. Can anyone give me any info???

Yes, you should retard the overall timing by 5 to 7 degrees. The width of the timing plug hole is about 10 degrees, so if you put the timing mark just on the front edge of the timing plug hole, that will be about right.
Oh, you want to know why to retard the timing on dual plug setups? Dual-plug heads are especially beneficial when used with hemispherical combustion chambers such as the shovelhead. With a single spark plug, the flame front must travel from the spark plug on one side of the chamber, up and over the top of the piston to the other side. When dual spark plugs are used, the flame front starts from both sides and burns towards each other in the middle. Because of this, the burning of the fuel mix is completed sooner, therefore the mix should be ignited sooner to maintain the timing of maximum cylinder pressure. To take full advantage of the dual plug solution, Yes--- retard the timing by 5-7 degrees. It works well for me on my dual-plugged '77.

[sclafan1]

timing

Rooster...your the man!....thanks for your help and quick reply....that's info I was looking for!

[Rooster]

Glad to help.
What else did you do to your '76? Single-fire electronic ignition? Cam? Carb? Exhaust? Stroked?

[sclafan1]

timing

ss carb....tired of messing with old old one, I guess it was just too worn to work properly...besides that and the double plug heads ...just strait pipes...sounds awesome

[Rooster]

Put a mild street cam in it, and that sucker will come alive!! No kidding, it will amaze you!
If you have slight stumble at low to mid-range, it could be from the straight pipes. The newer S&S carbs have an air bleed adjustment by which that can mostly be tuned out, but not eliminated. A little back pressure is needed to prevent the exhaust pulses from reversing direction and going back up the exhaust pipes and colliding with the out-going pulses. That effect is known as 'reversion', and some slight baffling will take care of it. But there's always a trade-off........... you would lose some of that gnarly open-exhaust rumble.

[The Professor]

ss carb....tired of messing with old old one, I guess it was just too worn to work properly...besides that and the double plug heads ...just strait pipes...sounds awesome

Don't be afraid of a CV carb.