update 84 720 4x4 running rough

[mattthruwalkin]

welllllll crap , i was gonna buy plugs n wires but figured i'd run a compression test on her first...... first cylinder (front of the motor) had 150, second cylinder has 150 and the third cylinder had 30 and the forth cylinder has 150 also , i have an exaust leek at the manafold where the pipe bolts in to the manifold , could this have burnt a valve , no water in the oil and she don't use water .... time for a rebuild ???? anyone know about how much that would cost to fix and what would cause m motor to lose pressure on the cylinder ? wondering cause i found a website to buy a new remanufactured z24 with a 4year warnenty or 1million miles for just under 2ooo$. (long block)

also how long will the ol truck last running on 3 cylinders ? happy holidays all

[Davezilla]

The exhaust leak could burn a valve but being it's from the manifold to the pipe makes it a little less likely unless it's a big leak and it's been driven on for a good bit at highway speeds or better... Let's not rule that out yet tho...
When you did the compression test in that cylinder did you try putting some oil into the cylinder and running the test again to see if the numbers went up significantly? If not, then put a small amount of oil into that cylinder (not too much, just enough to coat the top of the piston, like move that cylinder to TDC, then add oil) and run the test again.
If the compression goes up considerably it means the rings are shot but if it stays close to the same it's a valve issue be it burnt, bent, leaking etc.

That'll tell you rather to take the head off and do a valve job or to either do a complete overhaul or replace the engine.

[mattthruwalkin]

the exaust leak is a pretty sizable and i drove it over 300-400 miles from apalachacola fl to near orlando , i will try the oil trick tomarrow and post back ty for the tips or tricks and the speedy reply

[Davezilla]

I'd bet you burned the exhaust valve then if you drove it that far... That happened to me a few years back when my blazer blew an exhaust manifold gasket and I decided to drive it 10 miles to get it home instead of parking it and calling for help. Replaced the gasket and it ran rough with a noticeable power loss and sure enough... those nice stainless valves warp just as quick as the stock ones do...

You'll most likely end up having to replace that exhaust valve and getting a valve job done while the head is off and you'll be back up and running. The engine will run on 3 cylinders but I wouldn't recommend driving it that way... maybe from your house to the shop if you have to, otherwise, pull the head and take just the head to the shop if you can.