I'm new here, so bare with me. I'm not new to tbi, or building good street motors. I've got a new motor in my 93 c1500 and decided to build it. 355, ran perfect before, and now it's running too rich. My first thought was because of the cam, it's a 292/292 lunati, 108 lobe seperation with worked aluminum "vortec" heads, put it all back together, broke everything in just like I always have. It's running way too rich at idle, and rich (not much) higher than 1,000 rpm. New coolant temp switch, new idle air control, and plug, new map sensor, and distributor BUT the timing is going crazy on it so imma pull it back out, put the old one in and try. Timing is staying too advanced. Would plugging the O2 sensor help any? I've got headers with the plug ins for it. Never had any luck with chips, any ideas?

 

I only see one Lunati cam that is 292/292 and it is a flat tappet cam with 230/230* @ .050 duration and a 109* LSA. That cam calculates out to 74* overlap. If it is on a 108* LSA that is 76* overlap. A factory TBI/TPI/LT1/Vortec EFI cam is in the 30-40* overlap range. You are idling way too rich because your cam has greatly reduced the vacuum signal to the map sensor. As for the timing jumping around, you need to set the timing with the timing wire connector disconnected. To even think about making that engine run you need about 20* less at .050" duration and a custom chip.

 

Could you put a vacuum canister or pump on it?

 

Short answer, NO...Atleast not for the MAP sensor. The map sensor needs to see changes in vacuum so that it can adjust the fuel and timing for various engine loading. If you are trying to run this engine on stock injectors and stock fuel pressure its likely running too lean under load as well.