BlacKnightsZ28

Alright, I'm still kinda new to this, so I need some input. I have the car listed in the signature, and I need to jet my carb for my altitude, and to eek out some extra performance. I'm at about 4500 feet, and according to my Edelbrock book that should put me about 6% lean. But the jet and rod combos they list to use are either 4% or 8% lean. So could I use a little bigger jets with a smaller rod to average out to 6%, or what should I do?
I had a mechanic try and jet it for me, but when I got it back it was running like crap. Come to find out he had only changed the primary jets, and had changed them about 12% lean and left the rest alone. Any ideas? Please help!

F-BIRD'88

You don't need a mechanic to change jets on these carbs.
They've got to be about the easiest to change jets and rods.
Start with the primary side and put in the jet and rod that is 8%
leaner. Make sure you have the right step up spring to match your cams idle vacuum characteristics.
Evaluate this with idle, light cruise and light accelorations
(not into the secondaries.) If it surges go to a slightly smaller rod
(richer). Once you're satified with the primary side work on the secondary side. (full throttle acceloration)
Be sure your timing is not over advanced. get a advance timing light. Use high octane gas.
Be patient and make one change at a time.

F-BIRD'88

Try a .107 primary jet witha .065x.047 rod
Both these are in the edelbrock tuning kit #1480

Allow the motor to reach full operating temp before you evaluate it. As u go leaner away from the stock jetting,
the need to fully warm up the motor first will increase
but at that altitude, in the summer it should run a lot cleaner.
If this is too lean still , go to a 4% setup.

BlacKnightsZ28

So would it be better to run a little lean or a little rich? Which would give me more power?

F-BIRD'88

A little leaner or richer than what?????

You always want to stay a little on the rich side
at Full throttle. It will only affect power a very small amount
and helps avoid detonation.
If you tune lean to get the absolute best power then your
car is much more likeley to "run with the weather"
meaning it will be too lean on cool, clear, high pressure days with low humidity.
Usually if you get beyond 4 jet sizes either eway from stock for any reason, you've done something wrong or something else is affecting your performance.
If you tune for average to cool nice weather days (near stock jetting) you'll only be slightly too rich on the worse hot muggy days (but safe) and so will everyone else.
If you tune for the worse days[lean it out] (hot muggy) then forget to "rejet" for a cooler day, you'll now be too lean now and risk damaging your motor. And it will "run like crap" The best time to "power tune" your car is in the spring or fall. Then in the hot summer just go 1 or 2 stages leaner in cruise mode (rod change). This is the best compomise with the least amount of fiddling and the least risk of engine damage.

It's really hard to evaluate wether you are actually getting more or less power. Some people really fool them selves and get crazy with jetting. Traction will vary a lot more; run to run than anything else. But again the conditions are the best in the spring or fall for tuning. Watch your MPH at the end of the quarter
not the ET to see if you've made more or less power.
Any one who claims to be able to read plugs by color is full of ****. About all you can look for are severe danger signs on a plug
like overheating, detonation (severe lean) or super rich or a missing cylinder.
As long as your tuning makes you go faster (MPH) and there are not danger signs, ignore the color of your plugs.