sick 604, needs help

[jonboy2448]

I have a 604 with about 20 races since it was freshened. It all of sudden one night started popping. It idles good and sounds good till ya rev it to about 2500 then it starts popping. It still has decent power. The car will run top ten outta 20+ cars. I have tried about all I know to do (been through the fuel system cell to carb, the ignition system- new plugs wires and what wasnt replaced was changed out and another tried) I am wondering what else to check. Trying to avoid the big Fastrack rebuid. Any advice would be appreciated as I am a novice racer and even less of an engine man.

[Racer63]

Cracked header and or leak?

[Matt49]

Is it running hotter than usual?
Leaking header gasket or cracked header would be my first guess. Hopefully it's nothing more major than that. If it was a burnt valve you would likely hear a popping at idle also and you would notice a drop off in power.
If you haven't already, you might want to pull your plugs and see what they look like. That could tell you something. One or more fouled spark plugs could cause the problem you describe. You didn't flood it or run it real rich by chance did you?
I'm no engine expert but we pull our plugs every week just to make sure nothing off the wall is going on. I'd rather find out in the shop than at the track.
There are guys on here that know a lot more about these motors than I do though so one will likely chime in.

[dirty white boy]

is it poping out exhaust or carb??? if exhaust id be looking for cracked headers an blown header gaskets,..if its poping out carb an you done been over carb an dizzy,...id be looking at valve train...

[joedoozer]

Yup sounds like a header gasket. I had one leak last season and man did it sound bad.

[jonboy2448]

Its popping out the exhaust. I have not checked the headers or gaskets. I will b tonight after work though. Thanx for the tips.

[dirty white boy]

how bout a broken valve spring or a rocker come loose?
sometimes these, that ive mentioned will still sound good at idle.
actually a broken single spring will miss at idle and clear up as it gains rpm.
so mayb its not a spring.. but i wouldnt rule it out.ive seen it go both ways.
could be a loose rocker..

bent push tube,...i pushed a tube threw a stock rocker one time an it was poping back threw carb so hard i could see the air filter jump......