carb/timing question

[48junktruck]

Long story short: stock 350, small B&M supercharger, 600 holley. Trying to get it tuned and just cant quite get it. Plugs are showing super rich. Pops out the exhaust when you back off the throttle. Seems to want a ton of advance. Im way off the timing tab before it starts to run good. Id try to go more but the vacum advance hits the supercharger body. I could re-drop dist if need be. At zero on the tab it runs like ****. I guess a question would be: how can this thing be so rich? I figured with the supercharger im jamming a ton of air and if anything id be on the lean side. I guess im looking for any thoughts, opinions.

 

[fuzz]

Your 350 isn't going to run right at "o" degrees. You should set initial timing at about 8 degrees advanced without the vaccum advance hooked up and idle set at about 600 rpm. Hook up the vaccum advance and you should see additional 10 or 12 degrees. As you rev up the engine the centrifical advance weights will give you about 12 degrees advance for a total of about 32. You may have to pull and reset the distributor to get the timing correct.
A super charger pushes alot of air but also pushes alot of gas as well. You may have to rejet the carb to get the plugs to read good but try to get timing ste first. Let us know how it goes...[P

 

[PA41]

It sounds like your backfiring blew out your power valve in the Holley.

I've had the trouble, and replaced it with a plug just to tune it to prevent backfireing, but thats not good to keep, as it leans the motor on full throttle runs, and will somke your pistons right now..

I'm not a fan of the fartin, belching critters, Just had to have one to see for myself though.. Story of my life..

Check the rubber on the powervalve--betcha its busted..

PA41

 

[jfg455]

It sounds like your backfiring blew out your power valve in the Holley.
Check the rubber on the powervalve--betcha its busted..

PA41

+1. I would say it is junk

 

[Sam_Fear]

Does a supercharger change the way the vacuum advance reads?

 

[junker39]

48, besides trying the above fixes, you may want to check the TDC mark on the harmonic balancer. I've had a few that have had the outside "ring" turn on the rubber which throws the mark off TDC. Use the old straw in the spark plug hole trick to find TDC and see where the mark is on the balancer. It may be off a bit.