Head Replacement

[Dan1raysouth]

I have a 1998 GMC Yukon with 230000 miles. It’s running a cylinder 4 Misfire. Me and my buddy at work looked inside cylinder 4 spark hole and seen a tiny spot of rust on the right side valve so we’re thinking it’s a stuck because the other side was pretty wet. I’m pretty low on money so I’m wondering if I can replaced the head with one from the junkyard and if so will I be able to get by without taking the head to a machine shop? Or is it possible to have a successful end with out taking it to a machine shop?

 

[Schurkey]

WHAT ENGINE??? Diesel? Big-Block? V-6?

BEFORE you rip the head off, perform at least a cranking compression test, and--if possible--also a leakdown test.

Seeing "a tiny spot of rust" doesn't sound like a proper diagnosis.

 

[Dan1raysouth]

5.7l Vortec L31

 

[Dan1raysouth]

I’ve replaced the distributor, cap and rotor I have newer injectors, spark plug and wires, crankshaft sensor, cam shaft sensor. I hooked up a spark plug tester to see if the spark to the plug and i did see spark. Here’s misfire data.

 

[0xDEADBEEF]

If you can't get your hands on a compression tester, pull the valve cover. If it is stuck you may be able to free it up with some lube and various heavy instruments.

 

[Dan1raysouth]

Is that compression any good

 

[RichLo]

Not great but compare it to the other cylinders. It could just be how your running the test... be sure you pull the fuel pump fuse, have the battery fully charged and on a charger if possible, hold the throttle wide open and crank until the needle stops moving. Do that for all cylinders and compare the numbers. it should be +/- 10 or 15psi

 

[Dan1raysouth]

I checked the the opposite side of cylinder 4 I got 120

 

[Dan1raysouth]

Ok I’m going to do that when I get home today

 

[PlayingWithTBI]

be sure you pull the fuel pump fuse, have the battery fully charged and on a charger if possible, hold the throttle wide open and crank until the needle stops moving.

And remove all 8 spark plugs.