chris walrod

11.3:1 is the mechanical compression ratio by design, 200 is a dynamic pressure in PSI. These cars tend to range from 180 to 210 psi depending upon condition and warmth of the engine when the test was completed.

1-2% IIRC means the leakdown test showed that amound of static leakage in a percentage which is a great result. IIRC= if I recall correctly.

Land Jet

Still not hearing about the symptoms observed before having to redo the top end. Is it only the compression test or are there other tell tale signs? Because my car had a SCharger put on with about 80000 miles and no known rebuilds, a couple mechanics said I'm driving a time bomb and to be careful taking it to the track,etc. Wonder if they are trying to create work? I'll get a compression test next time I go in the shop.

fetus

Knock on plastic but my car has 80k and no motor issues yet. $1500 to fix the top and a couple thousand for the 60k maintenance, dash lights, trunk shocks, etc. And then the most important mods, HD Bilstein MO30 kit and 996 steering wheel. That set me back another couple of thousand but well worth it. I thought the stock steering wheel looked like my wife's SUV steering wheel.

VNTGSPD

My understanding is that the best evaluation of guides (apart from pulling the valve covers and checking each valve stem) is to track oil consumption. You can also un-scientifically check them by accelerating in 3rd year to high rpm, then coast down to low rpm before getting hard on the throttle again. During this exercise you will be looking for smoke from the exhaust.

The compression and leakdown tests are a good indication of the overal health of the engine but they don't do much for assessing valve guides, unless of course they are so bad that the valve won't seat properly.

Just drive it!

Caveman

88k miles and still, touch wood, all OK including shocks and clutch. I thinbk some of the lower mileage US cars go early due to your higher extremes of hot and cold plus the cars not being used enough...

deltawedge

As Chris mentioned the 200 psi is the pressure in the cylinder after compression. With a compression ratio of 11.3 and average atmospheric at 14.7 psi, this gives 166 psi (assuming 100% cylinder filling). The difference between 166 psi and 200 psi is due to the air in the cylinder getting hotter as it is compressed.

Steve Weiner-Rennsport Systems

Hi:

There are two reliable and accurate ways to determine whether one needs an upper-end rebuild or not: oil consumption and leakdown testing.

When oil consumption reaches 700-800 miles per quart (or litre), its time. Guides are worn out, valve stems are worn down to spec, and one usually finds a multitude of assorted oil leaks.

Leakdown testing shows the ability of each cylinder to hold a predetermined pressure and shows the percentage of leakage. Further, leakdown testing shows WHERE the leakage is coming from and thats something compression testing doesn't do. Pressurizing each cylinder while listening to the intake, exhaust pipes, and the oil filler tube tells the technician the general condition of intake valves, exhaust valves, & ring sealing.

I don't think those mechanics were misleading you or trying to generate business and I'd advise regular leakdown tests as well as careful tracking of oil consumption.