Hi. I have a question about my Edelbrock 1806 Thunder Series 650cfm carb. I was wondering if should change the secondary jets first or the primary jets? I am trying to see if I can pick up a little more power on the top end. It runs good now, but I am just experimenting. I just want to test whether or not I can pick up some power. Right now it has the pink rod spring which I believe is 7hg. It has the .065 x .042 metering rods and the stock jets. Those being primary(.095) and secondary(.098). Aren't the primaries usually larger than the sencondaries? Thanks for the help.

I am going to a dyno day and was wondering if anyone has any suggestions on what to change first? Mains or secondaries? Thanks.

the dyno guy will know. The stock jets are small, mine ran very lean even when it was a 327!

Ended up with 101's primary, .098 secondary, I forget which rods.

The primary's are bigger cause they have those metering rods stuck down thru them, closes the hole up a bit.

According to the Edelbrock website, the Thunder series 650 has a smaller primary and a larger secondary. Unfortunately the dyno runs are not for tuning. It's simply to see what the car will make. I get three runs. Forst one is power, second one is torque, and the third is A/F ratio.

According to the Edelbrock website, the Thunder series 650 has a smaller primary and a larger secondary. Unfortunately the dyno runs are not for tuning. It's simply to see what the car will make. I get three runs. Forst one is power, second one is torque, and the third is A/F ratio.

huh? Dyno will give all of those at the same time on one run.

That's what I thought, but that's what I was told.

IMHO, dyno time without tuning is kinda a waste of money.

Thats's how I feel. I am going to ask before I throw down $70. My Edelbrock takes a matter of seconds to change metering rods/springs and not that much longer to change jets. If I am going to pay $70/3 runs then I am going to get some tuning out of it. I was told they would give you suggestions after the pulls, but how am I supposed to know if they work or not? It sounds like a way to make money.

When would it be necessary to change the secondary jets? I have an Edelbrock and I also have their calibration kit, but it only gives main jet changes. It doesn't say anything about secondary.

At least theoretically, you tune the primary side for best all around driveability, and the secondary side for best WOT AFR.

According to the Edelbrock tuning guide that they include with the carb, all the increases are to the main jets. They show power and cruise being adjusted from the mains. I don't see how both can be from the mains. I thought the power was made by the secondaries, but they show you can go 12% richer on the power side by changing just the metering rods. Perhaps anything above 12% requires a secondary jet change? It's hard to know because when I called the Edelbrock tech line, the guy acted like he didn't want to be bothered with my questions.