so my truck (1996 4.9l) has been making a ticking/hissing sound for about 2 months now and i finally got fed up with it and decided to diagnose the problem. I thought that it could be a leak in my exhaust manifold but as i spent some time searching, i found that it was a hole in an unknown part. this "unknown part" is a hollow bolt (about 1/2" dia) that mounts into the head right by the interface of the valve cover (there are 6 of them down the passenger side of the head). this hollow bolt had a hole in the top of it but the other 5 were fine. my truck is throwing a 411 code which is a secondary air code.. could this have something to do with that?? I took it out, sealed it with high temperature epoxy, and the hissing/ticking went away but the code did not.. what is this mystery part!?

 

that is the air injection system, and they are known to leak. you can order a new one, good luck getting the old parts out. you can also weld the holes shut.( this is what i did-must remove the head though-(this i didnt do)

 

Six 1/4" NPT plugs will take care of the holes, but you can't do it if your truck is inspected.

 

they came out easily surprisingly.. what exactly are they called? and how much per part? i doubt that high heat epoxy is going to hold very long...

 

It's the air injection pipe, and it's one piece.

 

i think LMC has them

 

ok, are the holes yall are talking about the ones that would be on the back of both heads on a v8 model???

 

yep those are the holes

and actually it is 7 pieces, 6 "nuts" plus the pipe assembly lol

page 45 in the current lmc.com site catalog

and i have no idea where to get replacement "nuts"

 

yeah. ive got a 351. i just stuck spark plugs in the holes. works great.

 

It's one piece, the fittings don't come off the pipe unless you ruin it.