header leak or engine noise?

[fryedaddy]

i have a pecking or header leak i cant figure out.i have new header gaskets and i have a noise on the driver side.i pulled no. 7 plug wire and it almost stopped.it quietened down alot,could i have a crack in no 7 tube,headers are old and have cracked before or would it be a lifter or worn lobe on no 7?why did it get quiet when i pulled no 7 wire?

[cammerfe]

If the noise is purely mechanical---such as a lifter---the cylinder firing would make almost no difference. What you've described makes me lean toward a leak (crack?) in the header. if you 'crack' it in the dark you may be able to see something.

KS

[fryedaddy]

its pretty loud ,you can hear it over the exhaust,but when i pull the wire it gets so quiet you can barely hear it.put the wire back on and it gets loud again.i was worried about the lobes on the no 7 cyl. anyway because my cam is used and the engine i took it out of busted a sleeve in the no 7 cyl. i dont know if that would affect the cam or not by busting that cyl? a screw dropped down the carb and ended up in the no 7 cylinder of the other engine and ended up busting the cyl wall and beating up the piston,could that have hurt the cam and be causing the noise?i hope its a cracked header,im wanting some new ones anyway.how can i tell,im just a shade tree with few tools.

[cjshaker]

Like Ken said, it doesn't sound mechanical, and if you run it when it's really dark, goose the throttle, you may be able to see some flashing or flickers of light indicating escaping exhaust/flames from the combustion. Or if the engine is cold, start it and feel around the tube to see if you can feel any pulses of escaping air. You have to be pretty quick on that one though because the tube will heat up quick. If everything is clean enough, another way would be to look very closely for any dark sooty areas indicating escaping exhaust. You might have to crawl underneath to see the underside. If they've cracked before, chances are it's cracked again, or you've just got a bad gasket.

[Jim Comet]

I was helping a friend on his small block Falcon the other weekend an we had a ticking that we all swore was coming from the drivers side valve train. Pulled the cover and could not find anything wrong. Noticed a poor fit on the spark plug boot when we reassembled it and the noise was still there when we started it. We decided to address the spark plug boot fitment and when fixed the noise was gone. It was spark arcing to the header. Jim

[fryedaddy]

thanks guys,i really hope you are right about it being the headers.i will check the best i can for a leak tonight when it gets dark.i would love to put a new set of headers on and it cure the problem.thanks again.i hope its not the valve train on this new 433 fe

[shady]

a cracked piston skirt will stop knocking when a plug wire is pulled. usually worse when cold.

[fryedaddy]

i hope it aint a cracked piston skirt,i have a new set of speed pro forged alu. pistons in a fresh .30 over 428 block with less than 1000 miles on the engine.i think it gets worse when hot

[fryedaddy]

if you rev it up a little its less noticeable but still there

[Heo]

Dont think its valvetrain when it changes when you pull
the plug wire. Header leak,Bad bearing,bad piston pin bushing
cracked piston. To much  piston clerance in no 7

[fryedaddy]

after hearing all that,i sure hope its a problem with the exhaust

[fryedaddy]

i drained the oil and pulled the filter and cut it open,not a spec of medal nowhere in the oil pan or filter.i guess that tells maybe no spun bearing.if a compression test goes well too,maybe it could be a exhaust leak.

[C6AE]

Sometimes you can pinpoint a leaking exhaust joint by using a short length of heater hose as a stethoscope. Hold one end to your ear, move the other end basically from port to port. If it is an exhaust leak you can usually find it right away. (Sometimes the exhaust cross-over can leak, I found a manifold once with a pin hole burned clear through near the base of the carburetor)

[fryedaddy]

thank you,i have patched,scabbed,ground,and bent these old headers one time too many.time for a new set even if the problem turns out to be something else.

[Lenz]

I'm on board with a likely exhaust leak.  Experience has taught me that a leak can sound just like metal hammering metal.  Before you get any further you sure want to eliminate that end of it, everything else costs a lot more and might send you digging way deeper than you may need to.