Long story short, the engine is out of the car. Loose head/cylinder studs are the suspected culprit. I'm planning on pulling the cylinders to lap them into the heads before I put it all back together. Will this necessitate re-ringing? The rings have about 8,000 miles on them.

Thanks for y'all's help!

Konrad

10Kmi is the recommended interval that I have read in the manuals. It is not expensive, and "while you are in there" you might as well. Hone the cylinders, though or they wont seat.

Buy the girl a new ring/don't use the old one. Woops, wrong thread.

If ya use new rings, you should at least hone the cyls

Wait did you just say that 10,000 miles is the recomended interval to replace the piston rings?

Ring it if they're worn out, and hone the cylinders if you ring it. DO NOT USE A BALL HONE!!! I suspect the rings will be fine at 8K miles, unless they got really hot. Have the heads surfaced if they're the least bit "iffy". Lapping them in is a joke, and lapping them without milling the surface is downright criminal. When you cut the heads, shim the cylinders to compensate for the cut. Loose head studs are rare on a T4 unless they've gotten REALLY hot, and even then it hardly ever happens.

The Cap'n

What is the issue that you were having?

If you are rebuilding the top end, it would be silly NOT to hone and re-ring. its so easy on these cars since you can just slip the jugs out and hone them.

Zach

IF the jugs are pulled, the recommended interval is 10Kmi. I see where that could be confusing how I stated it before. You do not need to change the rings on an engine that is assembled every 10Kmi

John, why not use a ball hone?

A good machinist will set the cylinders up in a fixture to assure the hone is centered, round, and even. Not all that easy.

The Cap'n

Here's the background:

The driver's side lost compression on both cylinders. The head checks out ok, no dropped/burnt valves. No apparent cracks or voids. This leads me to believe that the studs have backed out a little. They are not loose by hand, but I suspect they have turned enough to break the seal between the cylinder and head.

The motor is a 2.0 Porsche case with 2.0 bus heads. My plan is to use this as a weekend driver until I can put a 6 in it, so I want to have a reliable engine, but without putting a whole lot of $$$ into it.

Konrad

How much compression? What was the leakdown, and where did it go? Are the valves seating? What do the gaskets look like (if there were any)? Was there any popping or other noise before you tore it down? Did it get hot? How hot, and for how long? If the loss was from the head/cylinder interface, you'd hear it and you could see where it was going.

The Cap'n

The leakdown cold went to 0 almost immediately. When it was warm, it would intermittently hold compression, but no leakdown was done while it was warm, so I don't have any numbers for you. I don't remember any popping sounds, but this was about 2 years ago. It definitely didn't sound like it was running right. It never got hot. I don't have any numbers, but my melt-off warranty tag has always been in place.

Thanks for your help Capt'n!

Also, valves are seating fine. The gaskets, around the combustion chamber (if they are gaskets and not shims) have some carbon build-up but aren't scored or torn up.

If you suspect head studs, did you re-torque and try the tests again?

Zach

to answer the original question.
re-ring it...hone the cylinders and do it.
Simpler now than later.

Rich