I'm running a 327-.030 over w/comp 268H grind cam, Pro topline heads, Edelbrock Performer RPM intake, and Edelbrock 600CFM carb. I want to get some opinions on opening the carb up to match my combo. I am running the 600 carb stock, and have read posts where a small jump up in jetting and a decreased metering block size can really "wake up" the carb. Anyone running a combo close to this? Is it worth it when I'm running such a mild build?

Thanks-Dano :beers:

I think the only accurate way to tell if you need to re-jet, is by running an wideband air/fuel meter. Most chassis dyno's have this option. Or buy an in car type.

Or you can do the trial an error method at the drag strip. Jet up until your mph stops to raise. But track conditions must be identical from run to run.

Another option would be to read the plugs. Do a WOT pass, shut the car off, and read the plugs that way.

If the car seems to be running fine, it's probably set pretty close to ideal.

Thanks Mark! I'm going to get the car dyno'd this weekend, but wanted to see if there is a "normal" metering block or jet size to try first...

Dano

While dyno runs and WOT will tell you how much TOTAL jetting you will need for the primary and secondary.....and thus to the floor power, it doens't tell you squat about all the other issues on the street. While you may have a WOT perfect setting, if it bogs real bad off the line or off the roll then you lose anyway! Ya got to to the tuning to get it right.

"opening the carb up to match my combo."
Never heard of this before and you certainly can't do anything but change jets/rods/springs/pumps and mixture screws.

The AFB has five distinct metering circuits. Idle, primary, secondary, transition, and pump circuits.

First, get the timing correct and USE VACUUM ADVANCE. You will thank me later. Set the mechanical vacuum with your tach then go back and use a vacuum gauge as per the manual to accomplish the "perfect" idle mix.

Second, if this is a relatively new carb.......change the step-up springs that boost the rods out of the jets. These carbs come with an "orange" spring and I would start with a silver or stiffest spring if you have over 14" of vacuum. This will help the throttle tip-in bog that comes with not enough boost. This is the most common bolt on complait of these carbs.....and is easily corrected with the stiffer springs. Oh yeah...buy a calibration kit for your carb.

Third....don't worry about throttle issues yet.......go and spend 15 minutes at cruising speeds on the highway. No stops or traffic. Then pull into a safe place and read..read...read the plugs. Should be "light sand brown". See this.... http://cochise.uia.net/pkelley2/sparkplugreading.html

After getting the primaries dialed in....then time for transition circuits. If you do not have a bog or hesitation then leave it alone. If you do, richen the boost springs or increase the pump dump. Usually the transition circuit will be very close with your cam. To really accurately get the secondaries dialed in......then take it to the dyno to complete the perfect dial-in. If this is a chassis dyno you may be able to set the primaries up too.

Thank You! That was exactly what I was looking for. I will buy the kits and read, and have my mechanic (friend) help out. As for "opening up the carb"...You have never heard of it, because I just blurted it out for lack of knowing how to word it. I guess I meant change the mechanical parts of the carb to suit the rest of my engine/drivetrain. Anyway, I will get to it!

Dano :beers: