I have a 350 lt1 with ported and polished head, 2.00 intake valve and 1.55 exhaust valve, new ring and piston, new opti, cc306 cam, 52mm throttle body, #28 LS1 injector, PCMforless chip,(1993) long tube headers,problem: the engine is running very rich, always black dust comming out of the exhaust.the mechanic said that i only have 13 of vacum and it supose to have 18 for the map sensor working properly. so he said that we could put a resistence in it to make it think that he is at 18. for the rest, the engine is very strong. Any advice please???!

 

13" of vacuum. Hmm. sure there's not a leak anywhere? I'd imagine your engine doesnt have a ton of miles so it' prolly isnt full of carbon deposit.s

 

Vaccum could be a problem along with alot of other things that combined could make it run rich such as plugs, plug wires, O2 sensors, etc. that was my problem until i fixed it and noted no smoke, better gas milege and i could also stand behind my car and not get a tear in my eye from the unburned gas fumes.

 

i thought #28 lbs ls1 injectors on the lt1 were only 18lb injectors? Wh yare you running ls1 injectors?

 

Mines runing rich from some holes in teh intake elbow causing induction leaks....

 

18lbs is too low. I thought it was more or less like 23lbs?

 

13" of vacuum... that's pretty damn good. I have almost the exact same setup, except 58mm t.b. and 30 lb. accel injectors, and Im only pulling 10-10.5" of vacuum.I have no intake/vacuum/exhaust leaks. I've been over my car with a fine tooth comb. I don't think your going to get anywhere close to 18" of vacuum with the big of a cam... my 10" is in the pretty norm range. for the cc306 cam. so yours is doing fine in the vacuum range. prob. need to work on the tune some more... I had to have alot of tuning to get it straight. it is close but could be alittle closer. the overlap on the cam is prob. causing some of the richness probs. I think alittle more tuning will help you out.

 

there from 18-22lbs, im not 100 percent sure. but they are less then lt1 injectors so whats the point?

 

lt1 injectors are 24lbs.

 

you're running rich because its a mail order tune. They are almost always rich because its safer to foul out plugs and get shitty gas mileage rather than run lean on one cylinder and melt a piston, get a dyno tune, should help out a bunch. My car runs rich as hell too on a mail order but im heading up and getting a dyno tune probably in a couple weeks.

 

madz28 tunes are not to bad for putting around town, but are very rich at wot. mine is 11.3 with my madz tune.