Initial Timing with Carbed 4.6

[bigblack'74]

Im trying to fine tune my 4.6 stroker. I need to know if there is a general consensus on initial timing with a carbed motor. I am running holley 4bbl and a single point dist. I have been setting it at 3 degrees btc. That setting doesn't seem to be correct.

Also what about running vacuum advance off straight manifold vacuum, or ported vacuum? I have got to get my initial timing right so I can work forward with adjusting the carb afterward. thanks

[John]

Try about 8 degree initial timing and use the ported vac for the dizzy.
John

[bigblack'74]

I actually got it up to 13 Degrees initial and found the sweetest spot. My main problem is that when I checked total timing at 2500 rpms, it took 59 degrees of dialback on the timing gun to get it to zero. So does that mean I have 59 total or 59-13= 46? Either way I guess I want no more than 40 at the max of total timing. I cant seem to find an adjustable vacuum advance module for this dist. so im guessing ill have to make a limiter for it.

[gonridnu]

You need to plug the vacuum advance to check total mechanical advance. If there is no load on the engine the vacuum will advance it another 10-15 degrees beyond the mechanical. And yes it is correct that it needs to be ported vacuum. I don't know these engines well but generally speaking 32 -38 total mechanical advance is a good number depending on the compression, burn rate, octane, altitude, blah blah blah ad nauseum.

[jcsj]

try 12 degrees initial and 28 degrees total, seems to work with the 4.0 combustion chamber.