Cracked header or more?

[Mel]

Our boat was running fine till the last day of vacation. We have wet headers and the drivers side header started leaking where the four pipes go into one. A new sound appeared kinda like a popping. Is this awfull noise just my cracked header or should I suspect anything else?? http://free.***boat.net/ubb/confused.gif

[MoJetBoPar]

Hi Mel,
I was gonna e-mail ya and saw this.
That sounds like a back-fire from air getting sucked into the exhaust from reversion. Did it happen when decelerating, letting off the gas? If your motor has a performance cam with high overlap it can do that. There is a very brief moment when both the exhaust & intake valve are open and a dose of unspent CO (carbon monoxide) or in your case oxygen that is leaking in will go into the combustion chamber and cause a lean condition or pre-ignition.
Are you guys gonna take your boat out again this year?

[Mel]

Hey Mo Jo,
The sound is there durring acceleration and holding a steady speed.. We would be taking her out again if we get a new set of headers just that I would be really sick if invested in the pipes and the sound was still there!! Yes we have a high preformance cam can't remember the durration tho did too many engines since this one. One thing for sure tho sound wasn't there untill we sprung a leak and the sound is as loud as the headers themselves kinda reminds you of a machine gun.

[Jetboatguru]

Mel check to see if the headers are cracked anywhere else, especially near or on the flange. If so, you are sucking air and that will create a backfire. Had the problem before. If so, go get them welded or drop the $700 spank

[MoJetBoPar]

Just a thought here Mel,
If that motor is making that noise all the time, even under load, ya might want to check and see if maybe something else weird is going on. Like when the 5 & 7 plug wires, that are adjacent to each other, they like to crossfire. Or pull the plugs and check to see if all seem to be firing. No carbon tracking under the distributor cap. If the plugs look white you may be very lean, vacuum leak or carb problem. Maybe it's a bad header gasket leak between the head and header.
That's allot to throw at ya but it's hard to tell without hearing/seeing it in person.

[Mel]

Hey Mo,
Forgot to mention that I changed all the plugs and wires at the lake as soon as I heard the noise. I also checked compression it was fine.. the popping was still there.. it seems to me the noise is comming from the side the header is cracked on.. No chance of welding where it is cracked.. There is no carbon under the cap and the plugs were not white. I guess I will just have to put a new set of headers on ! http://free.***boat.net/ubb/cool.gif If the boat wasn't so loud it would be easier to figure out!! http://free.***boat.net/ubb/eek.gif