Carb Jetting Question

[dipso]

Im twin plugged, 35 is way too much for twin plugged. Actually you can cut out 9 degrees of advance when you twin plug, 9 from 35 (single plug) is 26.
I started it this morning after letting it sit all night and it started real snappy. I was concerned about the 14 advance at cold start.
I drove it around it felt pretty good.
I'll go through the thing again one day and see if anything has changed, but I think the larger Venturi and larger Idle jet fixed it up pretty good. I probably didn't need the larger main.
If I do decide to put the larger main back in one day, I will have to get more air to lean it back out. But so far I'm pleased.
Going from the 145 back to the 135 really smoothed out the transition from idle to main. I could always feel the switch over at 3500.

[snbush67]

The twin plug is what allows you to add more advance. As RPMS increase you want more advance, but it's finding the fine line between advance and detonation. That is why you want to tune under load. Some tuners tune to the point of detonation then back off a few degrees. By having two plugs you have two sparks from different directions, that I think are milliseconds apart, so you can get away with higher compression and more advance. When balanced you can eek out a bit more HP, but remember that running your engine on the edge decreases longevity.

[snbush67]

Another thought, by changing out the jets you may have simply replaced a plugged or restricted jet, either way it's great that you have a good running engine.

[lindy 911]

Remember too that the cams you have will "come on" at about 3500. Sometimes it's hard to tell the difference between the cams effect on the power and the carb jetting. Just another layer to think about.

[dipso]

I think i am pretty good. If I increase the mains back to 145's, I would have to increase the air correctors to 210, since I have 190's right now. That would allow more air and fuel, because just upping the main made me rich. Air correctors come in increments of 20, right?
I would probably get more HP, more fuel more air more HP. But I think I will leave it for the time being.
Any guess on HP increase with a one step change in mains and correctors, if any? If it is 20, I'll do it tomorrow. If it is 5, I'll probably leave it alone.

[KTL]

Air correctors come increments of 5, just like main fuel jets.

[lindy 911]

There isn't 20 hp to be found in fine tuning the jetting from drivable. 5? Maybe, but I doubt it. Go have some fun.

[dipso]

Awesome Thanks guys.
I'll bring this thread up again if I decide to do some more tinkering.
Thanks for all the knowledge and advice.
Lance.