rosberg@ihuxi.UUCP (Rosberg) (11/05/85)
*Sorry...I lost the original posting from the person who thinks he needs to replace the rings in his engine, so I'll post it and hope he sees it. Apologees to those who are bored with this drivel. Are you sure it is the rings that are failing, and not the valve guides? If your exhaust puffs mostly (or only) when shifting, I assume you mean when the rpms are falling. If this is, in fact, the case, I would suspect the valve guides. The reason is that, when the rpms are falling (going down), the vacuum generated in the cylinders will have a tendency to pull oil down from the head (through the valve guides). (OK, I know it's a low pressure zone, and not a vacuum...no flames please). Before purchasing tools and/or parts, I would suggest you perform a compression check. You'll need a compression tester (a hose that generally screws into a sparkplug hole with a dial to register the pounds per square inch generated by the rising piston within the cylinder. Follow the instructions for using your tester (keep in mind that the closer to normal operating temperature the engine is, the closer to reality your readings will be). First, check the reading for all the cylinders (write them down, note any large changes between cylinders). Then, pour a teaspoon or so of engine oil through the sparkplug hole, and re-test the cylinder. If the reading goes up, your rings are shot (the oil helps seal the piston ring-cylinder wall interface). If the reading stays about the same, it the valve guides, and/or the associated oil seals. Replacing guides is generally something best left to machine shops and the like...it is very easy to turn a head into an expensive door-stop. Good luck. John Rosberg !ihuxi!rosberg
bcking@inmet.UUCP (11/08/85)
** this line up for grabs ** The oil trick worked fine for old flat heads but doesn't always do the trick in modern engines due to the shape of (some) of the combustion chambers and the placement of the sparkplug hole. For the price of a good compression tester you can get a serious tuneup shop to do a leak down test. Much more accurate. But in any case, the cost of the repair probably isn't worth the value of (this particular) car. R.M. Mottola Cyborg Corp. Newton, MA
rs55611@ihuxk.UUCP (Robert E. Schleicher) (11/08/85)
> *Sorry...I lost the original posting from the person who thinks he needs > to replace the rings in his engine, so I'll post it and hope he sees it. > Apologees to those who are bored with this drivel. > > Are you sure it is the rings that are failing, and not the valve guides? > > If your exhaust puffs mostly (or only) when shifting, I assume you mean > when the rpms are falling. If this is, in fact, the case, I would suspect > the valve guides. The reason is that, when the rpms are falling (going down), > the vacuum generated in the cylinders will have a tendency to pull oil down > from the head (through the valve guides). > > (OK, I know it's a low pressure zone, and not a vacuum...no flames please). > > Before purchasing tools and/or parts, I would suggest you perform a > compression check. You'll need a compression tester (a hose that generally > screws into a sparkplug hole with a dial to register the pounds per square > inch generated by the rising piston within the cylinder. > > Follow the instructions for using your tester (keep in mind that the closer > to normal operating temperature the engine is, the closer to reality your > readings will be). > > First, check the reading for all the cylinders (write them down, note any > large changes between cylinders). Then, pour a teaspoon or so of engine oil > through the sparkplug hole, and re-test the cylinder. If the reading goes up, > your rings are shot (the oil helps seal the piston ring-cylinder wall > interface). > > If the reading stays about the same, it the valve guides, and/or the associated > oil seals. Replacing guides is generally something best left to machine shops > and the like...it is very easy to turn a head into an expensive door-stop. > > Good luck. > > John Rosberg > !ihuxi!rosberg An added comment: To confirm a valve guide problem, go to some reputable repair place and ask for a cylinder leakage, or leak-down test. This involves blowing compressed air into each cylinder in turn, through the spark-plug hole, and checking for air escaping, either past rings, or past valve guides. With a stethoscope, the mechanic can usually pin-point the trouble area. This test, especially when done with a traditional compression check, should tell you where to concentrate. (I had very bad smoking during de-celeration with a Fiat Spider, and it was bad valve guides, not rings. Valve guides are especially troublesome with some kinds of overhead cam engines, depending on the way the cam "boxes" are designed. It is also fairly common for valve stem seals to be worn, even if the valve guides themselves are OK. Some designs rely totally on these rubber seals to keep oil burning low. Bob Schleicher ihuxk!rs55611 If you decide to replace valve guides yourself, get a good shop manual, as there are often lots of "tricks" that make this easy or impossible (things like heating the heads in an oil bath to remove press-fit guides; putting the new guides in the freezer to let them slide in easier, etc.) :wq