I have read many of the threads on this topic. Looking for some thoughts on what I have found and what I am looking at for solutions. Lots of smart folks out there and seems there are numerous options here. Maybe I am missing something or I just need to make up my mind......

Here is what I have in a 1980 C3

SBC 350, 8:5:1, Edelbrock performer heads, Weiand 142 blower and manifold, Holley 750 (4160) setup per lars. 700R4

Current dist is an ebay special with a hypertech coil.
Timing readings taken with innova 5568
Initial 16@700, 26@850 all in 48@4500, yes 48. This is AFTER replacing stiff springs with lightest ones in Mr Gasket kit 929G. So if I keep this I will have to restrict total mech advance for sure. I can add a stiff spring to get the top number down but that messes my target of 32@2800, and with the blower I want the insurance of no more than xx for total advance.

So is the ebay special good enough to tune and keep or is it smarter to get either a good stock HEI or pro form and curve it?

Since I have the blower I will be adding a BTM. I have the option of the programmable 6al-2 which allows me to control ignition timing. SO I could just lock out this dist and buy the MSD box, setup my timing map/maps via the laptop and call it good. I am leaning towards this. Lars used the BTM on his awesome 383 project but I have not heard from anyone on this forum who has used the 6al-s programable. IBANEZ 540 was looking at the same one and peaked my interest. Price is about the same so going with the 6al-2 might save me a few dollars in the long run. Just dont want to visit the dist issue later if this one is constructed of poor materials---plastic etc.

Then there is the topic of vacuum advance on a blown engine. Car is street driven and not WOT all the time so this does make sense or at least a timing map that can mimic it?


Let the comments fly.

 

I don't know much about blowers, but if your timing at idle (700) is 16, and the mechanical advance is giving you another 10 degrees in only 150 rpm, something is wrong here. Your mechanical advance should not start advancing timing until around 1200 rpm, especially with an automatic transmission. Then it advances another 22 degrees, but takes until 4500 rpm to do it? That's pretty crazy. Are you running any sort of vacuum advance?

Scott

 

No vac advance. I know thats what I thought too and why I asked about the ebay distributors and quality. So here is what I did a few min ago. I grabbed the heaviest springs in the set and put them in to see what happened

16@700
16@850
rises at round 1100
28@2700
36@4500

did not run it up past 45k,

no obvious binding in the plates, so my guess is heavy weights with lousy machining which gave odd results. The tighter springs cinch things up more and allow for more linear movement? Sounds good anyway
for now this curve is barely acceptable until I limit it which will be a little bit of a pain but not too bad. At that point I will go one step lighter on springs, check timing, drive it around and check timing behavior a few more times to ensure a consistent result. If it provides it then great if not then to the bin with the ebay dist.