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Two questions: 1978 280Z

896 Views 11 Replies 8 Participants Last post by  steves280
Just a couple questions today....How far should we go on the engine rebuild...burns a little oil, but compression test shows 157-161 on all cylinders. I suppose the seals and rod bearing since we have it out, but do I need to do valves? engine is dirty, bad gaskets around oil pan, and other items. Hate to spend a bunch if I don't need to. Many years ago I read that something can get clogged and increase the oil consumption...anyone know?

Second question...this is a California car from 78. Looks like smog pump has been removed......how may other components can I remove? Catalytic converter will be history.
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Just do the gaskets and bearings, re tap all the threads and chuck new bolts and screws. If it burns a little oil but has pretty consistant compression, you might only need to re do the valve stem seals.

Cheapest you might just have to replace the stem seals and sump gasket, cheap and easy.

ALL THE WAY. It would be crazy not to go ahead and get the head redone since it will be off. Also since you will be into the engine, go ahead and do all the bearings and the rings. The stuff is so cheap once you are inside the engine, just replace all the wear items. New injectors and a water pump too would probably keep it going another 20 years.
If you do a half ass rebuild expect half ass performance.
The rule of thumb is that if you have the head off and it's been 40K miles, have the valves and seats reground and of course new valve stem seals.
A '78 Z won't have a smog pump. One of the reasons Datsun went to fuel injection was to meet EPA rules, and the fuelie cars burned clean enough not to need smog pumps.

I agree with the above rebuild advice, except that with the compression #s you're talking about, I have a hard time believing the engine burns much oil. If it's "using" oil, I'm betting its leaking it somewhere. Unless you have the motor out and/or apart already, try just replacing seals and gaskets. 160 psi is excellent compression. Why spend all the time and $$$ on a rebuild if it doesn't need it. Do you have any symptoms that indicate oil burning? Puffs of smoke on startup, oily exhaust, etc?
Have you cleaned the PCV "stuff"? Do that first, fix the leaks and clean.
Then watch for leaks (which would also be vacuum leaks!) and monitor your oil.
These engines should go 200K+ without "rebuilding". To rebuild a otherwise sound engine is just throwing away money that could be better used somewhere else. I guess some people don't know how to tell if an engine needs to be rebuilt or not so just rebuild them anyway to "be safe"? My original engine had way over 200 and still ran strong.

The 78Z's had steel valve seats so the head shouldn't need anything. Many machine shops will sink the valves into the head etc and just make things worse! Sounds like you want to just pull the pan to reseal it and replace the rod bearing while you're there?

The only other problem you may have with the oil burning is stuck oil rings. If the engine is cruddy under the valve cover, it could be a problem. Also worn rob bearing can make them use oil so if they are down to the copper, you might have found the problem.

When you say "using some oil" what are you talking, a quart every 2000 or every 500? How many miles does it have on it? Need more info to advise what I'd try doing.
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Time means as much as miles on these engines. Rings can stick and start scoring the cyl walls, cams can rust from non-use, valve stem seals are long gone, guides are coked up.

For a few hundred dollars there is no reason to not REFURB it. Remember, it's a 1970's era engine with an unknown past. All new seals and an inspection is not asking too much for the poor engine.

Thank-you for the professional answer. I bought the car from a kid that only had it a couple months. I have no history on the motor, so I'm sceptical. No smoke, no idication of any problems. But, sinc I have it out (to get the tranny overhauled, and to tteach my 14 yr old son about cars......figured I'd do the smart things. I'd planned on bearings, oil pan gasket (it leaks) freeze plugs and valve stem seals. I'll know more this weekend when I open up the oil the pan and valve cover. I'm still determining whether I really want to take the head off.

Again, thanks
No, haven't started yet......I've never worked on one of these engines, so I'll get the illustrations out and identify all the emissions stuff.

Thanks for the support
Freeze plugs aren't the problem they seem to be with american cars. The originals are cadmium plated and I can't recall in 20 years of working on Z's ever seeing one rust through. Can't assume the problems a chevy has are universal!
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