random misfire what could it be???

[Lestrey]

  i dont get it so my 83 gmc 2500 crate 350 starts misfiring while im about to change out the rear end so that being done i go n try n tackle the misfire check plug wires that i've never changed before and two had been burned up by the ex manifold so change those runs awesome but today after driving 100 plus miles 2 east tx seats for bout a few hour its starts misfiring again bad like multiple but after sitting 30mins its ok still misfiring just not bad enough to where i couldnt get home this one guy told me it could be because my exhaust donut could b causing it because of its not keepin compression which sounds off to me and he also said it could be cause one of my mufflers is missing ( broke student)
what could it be???     oh yea i got some plugs others should still be good i'll have to check the wires again

[Lt.Del]

without punctuation, this takes extremely too long to read to figure it out. 
That said, welcome to the site.  Check your plugs ensure no fouling.  Check plug wires again and make sure they are nowhere near the exhaust.  I'd put a new cap and rotor on it if just to rule it out. Check timing as well.

[Blazin]

What SgtDel says. Did you change all the wires, or just the burnt one? Your exhaust has nothing to do with compresion. Compresion is made in the cylinders.

[Lestrey]

yes changed all of them and now i'm going to check the cap, rotor, plugs and wires again and thx.

yea the whole compression thing sounded like hogwash.

[Lestrey]

changed everything ignition but the coil and the disturber itself , still missing so its up to the compression test now does anybody knw what it should be reading for good compression on a stock 350?

[Lt.Del]

do you have original exhaust manifolds?  The reason i ask is my dad's '76, many decades ago, developed a terrible engine problem and I worked on the timing, carb adjustment, everything i could think of.  Found out the right hand exhaust manifold had one of those valves that close shut and open for EPA stuff, recirculating hot exhaust air back throught the intake to warm it up.etc....
anyway, the valve was stuck closed from rust,e tc....cause a lot of backpressure which no doubt caused the rough running engine.  didn't find out til we took the 350 out and put a 327 in there....that thing was sweet. 

[VileZambonie]

If it's a random cylinder misfire and you checked all of the ignition secondary circuits then check the ignition module. If you have no way to test it then just replace it.