The head is off. What now?

Little recap of my problem. In August just before a run, the check engine light came on and it started idling rough. At the end of the week long run when I pulled into the gas station at home I noticed the rough idle was MUCH worse, but I didn't notice it on the trail (well, maybe the last day). The engine code was multiple misfires code. After changing the TPS, the distributor cap (which was already new), the coil, etc I decided I better check the compression. #6 was very low (~34psi) and #1 was ~134 psi, the rest were 150-160. Wet compression tet in #6 jumped the compression to 110psi so I figure it has bad rings. Over the last few month's I've been taking the heads off in my spare time.

So, here are the pics of the head and cyclinder. I have no idea what I'm looking at, so any suggestions would be great.

I'm hoping to just replace the rings and put it back together, however that is best done (all rings, just #6, new bearings etc???). What I want to avoid is completely disassembling the engine and getting everything mchined, if possible. This vehicle is soon to become trail/trip only for the mst part.

Thanks

http://pages.sbcglobal.net/basalt51/Engine/

I wish I had a chance to talk to you before you pulled the head. Most likely the rings on #6 simply got stuck. There are ways to unstick them with them on the vehicle, but not so much with the head off.

At this point, I would see how much of a ring land there is at the top of the cylinder and if it is not bad, you can pull the piston out from the top, unstick the rings and replace the piston. If the ring land is pretty high you will need to get a reamer and take the land down a bit to accomplish this.

While it is always better to replace with new parts and bore the cylinders, if it is going to be a trail rig only, I wouldn't waste the $$$. Once you get the piston out verify that you don't have any broken rings. The pix of the cylinder walls does not show any galling so most likely they are simply stuck. I would put the piston face down in a pan of Castrol Super Clean over night and let that stuff disolve the deposits on the rings. That should loosen them so you can remove them without breaking and clean the gunk out of the grooves. I would lightly hone the cylinder then put the piston back together and insert it. Don't forget to put a dab of oil on the cylinder walls before starting. It wouldn't hurt to put a tablespoon of ATF in the other cylinders and let it sit for a few days before starting. It will tend to loosen the gum holding the rings since it is highly detergent.

Castrol Super Clean is the most amazing thing for removing those hardened oil and varnish deposits you will find.

I would then run a can of BG44K through the gas to help remove deposits on the rest of the pistons. More than likely that will cure or at least significantly help your compression problem. If not you are looking at pulling the engine and doing an overhaul.

Also remember if you hone, to try and trap as much of the residue as possilble and then pull the pan plug and drain the oil. With the piston out, I might even pour a quart or two of diesel through to rinse out the pan before putting oil back in.

If you find a broken ring and the cylinder still looks fine, you can hone the cylinder more and just replace the rings. Do not use chrome rings for this, use the plain old iron rings, otherwise you will most likely never get it to seat. Since you can't buy rings for only one cylinder, you might think about a complete rering job. I have mixed feelings on doing a cylinder that has good compression. Leave a sleeping dog lie.

Doesn't look too nasty in there - you can probably get away with a re-ring job.

Clean the head deck and block deck with Scotch-Brite, and you might want to give the pistons a scrub as well. You should be able to get discs and a backup pad to use in your drill - the 2" size is probably best. Get medium and fine grade.

You will also want a cylinder hone - I couldn't see much detail, but the cylinder walls look pretty shiny now so I'm assuming your original cross-hatch patters is worn off. You need that to seat the rings, or your compression won't be up to scratch. You run the cylinder hone in and out, working to get about 60* off the vertical between lines on the pattern. You probably son't need anything stronger than fine stones for that.

While you are in there, I'd mike out the crankpins and change the rod bearings. I say to mike out the crankpins because you may need a slight undersize, or have a crank that was reground from the factory (it happened.)

5-90

Thanks for the responses. I'll start with getting the piston out and go from there. It would have been nice to unstick the ring without taking the head off but too late now

Do you think there is any point in getting a valve job at this point?

And how do I get the coolant drain plug out of the block? It's a square drive but my 3/8" is too big and the 1/4" is too small.

also, if you hone it, to help with the residue, wipe the cylinder down with a paper towel and WD40, it will pick up alot of the little stuff and help to prevent any rust, if your not sealing it up right away.
For the valve job, I wouldnt necessarily worry about a valve job. but it the heads of, you could get everything hot tanked and the surface cut. a mild cut so that you dont gain to much compression or loose too much valve clearance. But it all depends on how long and how much you drive this... its always easier to do everything at once, than when you have problems down the road...

You must ream the ridges! If you don't new rings will brake very quickly running into the ridges. Also it'll be very difficult to get the pistons out past the ridges.


Been there
JoBo