which ignition timing curve?

[torjan]

Hello,

i've done some upgrades for my regal and having the Problem which timing curve should i adjust.

Engine is a '84 305 SBC LG4 none electronic, none cat.
Stock head & valve, cam, 8,6:1 compression, sparks
SMI-4bbl-Rochester-Carburetor Stage 2 (redone and calibrated carb, http://www.smicarburetor.com/ )
GM Performance 10185063 dual Plane intake with functional EGR
Corvette Ram horns 2,5" with 2x2,5" exhaust
MSD 8365 HEI with vacuum advance
Super (in Germany 95octane) Gasoline

initial for the stock engine should be 4°+-1 @ 450-550
is this ok? or should this be another
which stop advance bushings should i use?
which centrifugal adjust makes sense?
vac advance should be adjusted in drive with a wideband sensor i think, but are they any experience here?

thxs for help 🙂

 

[Phoenyx]

Sorry to change the subject. But we can fit ram horns in g-bodies?

 

[torjan]

no one any idea? 🙂

to ram horns
haven't installed them atm but looks good to fit, tight but ok, looking forward to get an apppointment at my exhaust builder to max end of october (or the next date is at april)

 

[megaladon6]

well the 4* is the stock base setting. it's for emissions but needs to be increased for power. and since you have some mods to help out the engine you definately want more advance. since you can us 95oct i'd go straight to 10* BTDC and see how it runs. that's at idle with the vac to the dist plugged. when you rev the motor it should go to about 25-30* i think. it varies with every component on the engine.

 

[torjan]

ah ok ty, that means that i could leave the stop bushings @21 (stock msd setting) (10BTDC plus 21 mechanical)
which RPM could be recommended to have the max advance (atm its 4000)

 

[85 Cutlass Brougham]

Honestly, it's something you will need to experiment with. Normally it is set up with something like 10 degrees initial and 36 degrees total advance (mechanical) coming in by 3,000 RPM or so. Also, I will caution that European octane ratings are derived differently from US Octane ratings. European numbers come from a single test while US numbers come from an average of two different tests. Even so, with the low compression you have, you should be pretty safe from detonation unless you do something stupid.

 

[torjan]

should i go max 30 or 35?
at the moment i changed the springs to get 21° @2900 and complete with initial i'm @ 29° and the engine runs nice.
if 35 will be ok the next step i'll try changing to 25° @2700 to land @ 33° (using other springs AND stop bushings),
for the last step i think i'll go from 8 to 10 initial. to have a max of 35
is this ok?

to the gasoline here
i think the super i use (95 octane) is between regular and premium in the US
http://en.wikipedia.org/wiki/Octane_rating