Ok so I have a 355 with the vortec fastburn heads on it, a comp cams xe268H cam, 224/230 & .508/.512 with 1.6 rr's 110 LS. Has the performer RPM intake, 1 5/8 headers, 9.5ish to 1 compression, hooked to a 200R4 with a 2800 stall, and a 4.10 12 bolt, all under a 3600lb Monte Carlo SS.

I can't get this thing carbed right to save my life. I have a vacuum secondary holley on it right now, it hates it. I tried a mechanical secondary on it before, it was much better. Anyone have any thoughts on where to start? I am not much of a carb master, I am capable of jetting it, springing it, accelerator pumping it etc, but cannot seem to get a good place to start. Help me oh carburetor gods!

 

What specifically does it do? Rich idle, backfires, poor top end... all of the above? I presume you started with the basics like float levels & idle mix and there were no problems there. Your combination isn't that radical, so the factory config with 71/76 jets is probably a good starting point.

 

I had many problems with my old 770 holley so i just went and bought a brand new speed demon 750. Runs like a dream. What kind of problems are you experiencing?

 

He never actually said what holley he was using. depending on the holley carb each one has it's own little quirks... I have a Holley 4160 VS 750.. thing was a pain in the butt..(and still is) but i have gotten it pretty close.. Did you buy it new? or was it used? if it was used what model was it? a stock 4160 comes with a 65 front jet and a 70 plate with the 30 cc pump and a the red cam.. and a black spring. Also comes with the 65 power valve (6.5) Never know if it backfired on you you might have poped the powervalve... which makes it pretty frigen hard to tune the thing... either replace it or block it.. but a blown one is just a headache.