I am learning how to work on Carbuerators now. The vacuumn secondary Carb in my Corvette has always ran rich and the plugs were dark chocolate in color and the exhaust tips looked black.

I put a kit into my Holley to replace the metering plate with real jets. I have 71's in front and 76's in the secondaries. I redid the idle at the same time I replaced the metering block and put in new plugs. It is too wet to drive the Corvette but I had to move the vette into the garage from the shop and as I had to start the engine I let it run until it was fully warm. I had it idling for a bit over 20 minutes. It never loaded up at all and ran great.

After I put it in the garage I pulled a plug to see what it looked like. It looked like it came out a new car with the tip still nearly white and the elctrode strap was spotless. So, I think I have solved the running rich issue.

I am now wondering what to watch for to determine if I need to fatten the primaries if it is too lean in normal cruising. I want to get that right before I start trying to tune for best ET! :D

Look at this post I where I put up an atical from Lars on holly setup

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=5;t=003050

One thing to look for is surging. If it surges (or seems like it is a little bit) while holding steady at 45-50 mph, its probably lean. I suppose you can back down a few jet sizes from where you are if its not surging- but I bet you wind up back where you are at. Dont make changes of more than 2 sizes at a time though- at least thats the "rule". You cant tell what the jets are doing at idle on a Holley- unless, your idling at 1200.

Really, though, like the LARS article says, do a full bore run and shut it off at the end with no idling. THEN check the plugs. IF they are that clean, quite frankly, Id leave it alone. Idle and Jets are two separate circuits on a HOlley, unless of course your idling on the jets tongue.gif , which it doesnt sound like you are doing.

If you have access to a strip just make a couple passes and record your MPH. Then lean it out in front and make another pass. If the MPH went up, you made more power and you should try leaning it out again (now go smaller in back - keep the jet number spread front-back close to what it was stock). When the MPH goes down, you know you went past the optimum ratio.

Reading plugs is pretty tough, I prefer to test at a dragstrip.

i have a 750 vac sec holley 3310-2 and my bbc i run 72 primary's and 76 sec........the rear was converted to a block........anyway.......i felt the effect of lean when i shoved 66 jets in the primary...did it just to see what it would do.............makes the car feel spongy you step into it you really not going anywhere......

im at about 1500 above sea level........and at the race track going from 70 to 76 in the primary didnt make much difference in my e.t. or my mph where it counts.......

and with the sec. i ran 76 to 80 with out alot of nothing going on........so for now im running 72 and 76 jets.......and seem to be just fine...........until i can get some more track time to dial it in alittle better.......