I have a 1995 cavalier with a 2.2l engine and a 5spd trans. What is the maximum amount you can shave off the cylinder head and still use the stock pushrods?

William Riley wrote:I have a 1995 cavalier with a 2.2l engine and a 5spd trans. What is the maximum amount you can shave off the cylinder head and still use the stock pushrods?

The issue is that the geometry of the valve train uses fixed dimensions on the 2.2. We are assuming here that the GM engineers did their homework and that when the STOCK head/block/valvetrain are assembled, the lifter is centered in its hydraulic travel.

The hydraulic lifter uses a piston inside the lifter body that is pushed upward by oil pressure. A one way valve allows oil to be trapped inside the lifter body and the valve train is automatically adjusted. The piston/lifter body fit is very precise so that when the cam moves the lifter/push-rod/rocker arm/valve/spring, it doesn't lose much, if any of the oil in the lifter that is taking up the space. The valve spring is strong enough to prevent the oil pressure from over filling the lifter, as long as the RPM's are kept within reason. Over revving can cause inertia of the valve/spring to open up a small gap in the valve train that allows oil pressure to "pump up" the lifters, which holds the valves open too far, causing a misfire, slowing the engine.

Let's assume there is .120 travel within the lifter. If the lifter is centered in its travel by the engineer's design being well done, then there is approximately .060 to be removed from the cylinder head surface before the lifter will "bottom out" and essentially become a solid lifter. The problem here would be that even when the cam is not pushing the lifter up, I.E. on the "base circle", the lack of hydraulic travel would still push the valve open slightly. I doubt that the engine came with super accurate dimension in the manufacturing process, but probably had a significant "fudge factor". It would be a good idea then to limit how much you shave the head.

Is the purpose to level the head after blowing a head gasket or are you looking to raise the compression ratio?

For just resurfacing the head a small amount because of a warp or corrosion, I guesstimate you could shave .010-.020 and still use the stock push-rods.

If you are looking to raise the compression ratio, the simplest way is to install pistons from the 98 and later 2.2. It is possible to do this without removing the engine from the car, too. They have a .030 higher compression height (the distance from the center of the piston pin to the top of the piston) and the dish, or cut out area on top of the piston is also smaller. You can do a search on the site for more info, but I believe the compression ration ends up around 10.8:1 if nothing else is changed. If you shave the head too, you could easily end up with a compression ratio over 11:1 You'll probably end up having to run premium fuel all the time to avoid detonation. One downside for the 95 year model is that nobody makes a programmer to modify the fuel/ignition computer settings.

On a side note, I've wondered if it would be possible to adjust the height of the rocker pivot studs with precision, hardened shims. One of the aircraft engines I used to overhaul used fixed geometry valve-train, but the lash was adjusted by shims. (Lycoming O-320H2AD)

hope this is helpful
dennis