What size should I go with? Auto lite 104 plugs, 180 therm, 3in downpipe, fender well intake. I'm thinking I should be good to go with 3.4. Opinions an experience please!

2005 monte ss sc

 

To be honest i'd start with a 3.6 scan for knock and go from there. While you do have some supporting mods, you dont have alot. Always better to be a little cautious, if you get the modular pulley setup you can always swap out for a smaller one. You might be able to do 3.5, but i feel like you'd get too much knock at 3.4 with your current setup.

 

From personal experience, I had a Plog, 3" DP, 180 tstat, 104's, ported sc, and was getting upwards of 10 degrees of knock. It took ported heads to run a 3.4 pulley with minimal knock in my case. My best advice is SCAN SCAN SCAN.