I've just finished doing an intake and exhaust modification on my 300 I6. It now has a Carter 625cfm 4 barrell running into an offenhauser dual plane 360 intake, exhaling through what I believe to be hooker full length headers, which dump into a clifford performance x-pipe and then through a pair of hooker super competition mufflers. All exhaust is 2 1/4''.

I had it running on a parts carb that only had the primaries functioning and it ran pretty good, but I wanted the secondaries to work so I swapped on a new carter and a 1 inch carb spacer by Mr. Gasket to get the linkages to clear. The new carb is dumping WAAAAAAAYYYYY too much gas and now she's caughing, sputtering, and overall just not running right. I know some guys on these fourms are running a similar setup, so I was wondering how to set the idle mixture and what I should do to keep the secondaries from cutting in until around 3000 RPM, or at least under heavier throttle. Also I was thinking about taking the primary jetting from the parts carb and putting it in as the secondary jetting on the new carb, both are identical carter 625's. Any help appreciated.

 

im gunna take a crack at this, but im far from a carb expert (but in learning everyday).

first, what type of secondaries is it running?
second, 625 cfm is rather large on a 300. most shoot for 390-500 cfm
third, from what i read (this regards holleys, but should be the same for any) to set the idle mixture u should install a vacuum guage and set it to achieve the highest manifold vacuum at the highest idle.

also, are the floats set correctly?

oh and, could u get a sound clip of that? id like to hear what an X pipe sounds like on a 300 with headers.

 

I bought the carb on ebay, don't know the secondaries. I know it's high (really high) But I've heard it done before and the old carb was the same size, it just didn't engage the secondaries. I'm not sure on the floats, but it's worth a check. If I get it running right I'll give you a sound clip. Right now it'd jsut sound stupid with it sputtering and all.