Pops in exhaust after replacing valley pan

[7dcuda]

I just installed the FelPro valley pan on my 440 that has the blocked heat crossover.  Now when it's cold, at idle, I can hear small pops in the exhaust that go away once it warms up.  It wasn't doing this prior to changing the valley pan and the only change done was replacing the valley pan.  What would be causing this?

[edison1970]

I would check for vaccum leak.

[HP2]

x2. You sucking in unmetered air and leaning out the mix in the cylinder.

[7dcuda]

That was my initial thought but I'm pretty confident in my pan install.  If it was a vacuum leak wouldn't it do it all the time though?

[jimynick]

Take a can of brake cleaner and squirt the manifold/head junction and see if the rpm changes. WD40 also works but leaves a residue. A non lit propane torch also works. Good luck. 

[7dcuda]

I had already done that and no leaks were detected...have since found the problem tho....the carb idle mixtures screws were adjusted too lean. 

[jimynick]

Great! All's well, that ends well, eh?