Hi
My 355ci was TBI and now converted to carbed and cannot find the way to a lean mixture!

Plugs are blacked out and rich mixture!

I am running with a Holley 750cfm vacuum secondries with 1st jets 75 and 2nds jets76 with a 510/507 lift cam and 9.5:1 compression

Now changed to 70jets on 1st and 75jets on 2nds and still too rich!

any suggestions with jet sizes??

 

get some plumber silver solder
get some flux
take a solder gun and fill the hole
redrill to smaller sizes until you get it to where you want it.

here is a cheap mm sized set of drills
http://www.micro-tools.com/store/ite...emCode=82616MD
http://www.micro-tools.com/store/ite...emCode=82615MD
drill bit conversion table
http://en.wikipedia.org/wiki/Drill_bit_sizes

Since I already had everything, it cost me nothing to experiment with different jet sizes.
ACE hardware sells the wire number gauge drills in my area.

 

Do you have a fuel pressure regulator setup in line? The tbi fuel pump will push 12-13 psi with no regulator holding it back. You'll need less then 9 psi for it to run well. I usually start tuning with the idle screws first. Hook up a vacum gauge to monitor what your doing to it. The higher the vacum the better the motor likes what you are doing. Put it in drive after it's warmed up and pull the e brake to hold it in. Then adjust your idle screws until its smooth with the highest vacum. Adjust the float bowls to just below the windows. Then change your primary jets accordingly. Followed by secondaries. Should get you close. You may need to change the secondary vacum spring so it opens quicker as well.

 

My car is manual and the fuel pump is mechanical with no pressure regulator and its 7psi

 

I haven't done it on a manual, but you should be able to get close with it in neutral. Just maybe add an extra 1/8 turn richer on the idle screws to compensate for being in gear. Start with both of them all the way in then adjust out 1/4 turn at a time going back and forth. Once it idles perfect move on to the jets. Read sofaking's sticky thread in this forum. That's what I used.
It may not make a big difference but I think the carb manufacturers suggest mechanical secondaries for manual tranny cars. Good luck. Oh and I was running 60 64 jets in my motor on gas. So you may have to get down into the 60's on the primary side.