Changed my cast Iron intake with a edelbrock performer back in april and changed all gaskets, along with the gasket between the intake and waterpump

In august I noticed some coolant on the front edge of my valley pan below the intake
I made sure the thermostat waterneck was tight and no leaks

I already loosened the intake bolts and the long bolt into the intake and tightened everything up (but didnt want to OVERTIGHTEN the long bolt)

I'm still getting coolant

Is there anything I am missing? Is there an easy way to change out the gasket without making a mess?

Thanks!

No easy fix. I'd get a hold of a pressure tester. Pump it up and figure out where it's leaking. If it is the joint between the intake and waterpump, no choice but to either remove the intake or remove the timing cover to reach it. I wouldn't rule out the rad hose or neck as the leak. I fought a leak at the rad hose neck for years.

So that E-brock came with a gasket for that location? The original used a rubber o-ring type seal. If you end up pulling the intake (which I suspect you will have too) Try and get your hands on the rubber seal if you can (that's even if it would work with the E-brock) Or you can just get some gasket material and make a new one and USE 3M Super weather strip adhesive liberally on the gasket. When you put the manifold back on, only snug the bolts up and then use that long water pump bolt with the tab to pull the two mating surfaces together...then torque the manifold 45 ft lbs i think.

Yes the Performer has the rubber seal, I put a light film of silicone on each end to help sealing.

loosen the intake bolts then tighten the long bolt then retorque the intake bolts

Why i always recommend separating the water x-over from the intake before installing.
Other is to get better intake to cylinder head alignment.

This.

And I usually just start to thread, definitely not snug, a couple of intake bolts before I tighten the long bolt in front. Now that the intake has already been torqued down you might need to lift it up before it will move forward. And I do what Mike says as well but I do it to make intake swaps cleaner, I never had a problem with a leak there but it's a good idea.