hey, sorry for asking i know there is a bunch of threads on this topic but i wanna be sure.

I checked ccmpression with engine warm and all plugs out on my 78 280z and all numbers came out 150-158 range. i know from reading previous posts that that is the minimum range for them to be at. but some people also say around 160-170 is what they look for. Do i have anything to be worried about?

The problem is i parked my car for about a year and now when it runs it blows a small amount of light greyish/blue smoke out the tailpipe. (whats odd is that it doesnt do it all the time, its off and on)

I took all necesary precautions before starting it i'm just worried cause it seems like its running a little rougher than it did before (thinking it might b timing) and im trying to trouble shoot.

thankyou

sam

You probably have a sticky valve. Not unusual for an engine that has sat for so long. It should improve with frequent running. Use a light oil (10w-30) in the engine until it goes away.

The compression test you conducted is just about useless. A differential compression test is a true diagnostic tool. This type of test can provide you with information such as which valve may be sticking, if the rings are bad and a host of other useful information.

It's the difference between cylinders that is important on a cylinder pressure test. 150/158 = ~95%. That's in spec. and pretty good. 80% is the worry point according to the FSM.

The volume inside the gauge can have a big effect on the pressure numbers. That's why the actual pressure reading is not too important.

I had puffs of smoke on startup and between shifts. What fixed it for me was new valve stem seals. While I did pull the head and did the valve seals at the same time, it is possible to do the seals w/o pulling the head.

I had puffs of smoke on startup and between shifts. What fixed it for me was new valve stem seals. While I did pull the head and did the valve seals at the same time, it is possible to do the seals w/o pulling the head.

A second to valve stem seals Lee. I was getting a bit of smoke after a down hill on a trailing throttle. then accelerating, which is symptomatic of valve stem seals gone hard.

I did the job in a couple of hours with the head in place. You need a spring compressor that hooks under the cam, and stuff as much cord into the cylinder as you can to hold the valves closed. Or compressed air into the spark plug hole. via a special fitting in place of the spark plug. to hold the valves closed..

Your comp is OK.

Brian.

Edit. If you havn't done many miles on it, you could find the comp. might improve as the rings settle down again. There could have been some surface rust on the cylinders walls. This could also account for some smoke.

Edited July 15, 201212 yr by olzed

I am curious, are the stem seals just a rubber part so they just pull off once the spring is compressed? If they are metal do they just unscrew to get them out?

http://www.geocities.com/inlinestroker/seals.html