Sudden pinging/knocking help please!

[Firechief70]

ok i will start with what i drive...98 tahoe 4x4 4dr. 5.7 with 219365mi..
been starting a little hard when cold and when it startas it runs real rough for about a min. then evens right out...been gettin worse and worse for last month...then on my way to work sun. out of the blue at about 40mph it started running feal rough and started knocking/pinging on right upper bank of the engine....iol pressure still at 65lbs , not over heating and only dose it under load...put the truck in park and rev it up and cant hear it until i get to about 2000-2500rpms.....ok thats that...now i will tell you a little more about what has been done .....i changed the fuel pump on christmas day only because it just failed, was running rough before that went bad...also about every month to month in a half a have to change #4 and #6 spark plugs i get the missfire code for those cylinders...just those two.....so there you have it....i have done nothing to it since it started this on sun. so i am begging for some where to start on wed. morning...any help would be great!!!!!

 

[SunlitComet]

check compression on those cylinders. I think you just blew out the gasket seal between between them. Ironically mine did the the same two cylinders. just out of chance. http://www.tahoeyukonforum.com/forum/showthread.php?t=26610

You will find the pic on how the gasket blew in there.

 

[Firechief70]

update!!!!!

did a full compression check on all cyl. #1 #2 #3 #5 #7 #8 all 175 or a little above....cyl. #4 just 20 but bleeds right down and #6 big fat 0 psi.....guessing this is not good at all?

---------- Post added at 12:57 PM ---------- Previous post was at 12:54 PM ----------

would a blown head gasket make it ping or knock?....before i get into head job!