1979 280zx L28 Engine Rebuild

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I recently got my car back from the mechanic, he did a compression test and determined off of my very low 60-60-61-60-62-67 results that I need a new engine, or I should rebuild mine. I live in California, so paying a mechanic to do it is just outrageous (~$85/hr) I've never done anything like this before, but I do have my dad to help me and it would be a fun bonding experience to rebuild the L6 on my Z. I'm all-for rebuilding the engine, but I'm wondering if there is a way I can test whether it's the valves, or whether it's the rings that are leaking. I'm assuming it's the rings, since that's what the mechanic suggested. It's hard for me to grasp exactly how long this will take, how much money in tools and parts it will be, and what else I have to do, that I haven't accounted for.

I've done a bit of research and found that I would need to grind the vavles, get new seats, change the rings, get a rimmer and rim the block, as well as hone it. I'd need to mic-test the crankshaft and change the bearings, get the bearing tension correct, buy an engine lift/cherry picker, and a complete gasket kit. Someone said I should "Get my heads done" I'm not certain I know what that means. My budget is about $2,000. My experience fixing cars has been valve-cover gasket replacement and changing my own oil (although, I've never had a car with a bad engine before so I never had the opportunity) The bad: She has 131,086 miles on it, I have no idea how long it will take to repair, 4 weeks? 6 weeks? the interior is pretty gross, and the electrical system has at least two separate families of gremlins living in it, it's an automatic, too which = yuck.

I'd like some advice as to where to start with this terrible news from my mechanic. Should I try some "engine restorer snake-oil" first? or would it more worth my time to buy a different (turbo or n/a) 280zx engine from a local wholesaler/ebay. I originally bought this car to drive for only about 10 months, which I would then later buy a car I would keep for a long time. The 280zx is that neo-classic style that no one really appreciates because it's got the 80's styling, Un-like the 240z-280z which is truely a 70's classic car. I'm certain it would be worth fixing if it were the old body style, but there are other 280zx's on craigslist for $900-$1200 with minor problems.

I can rebuild the motor, replace the motor, or replace the whole car. Tips/tricks/advice 2cents are appreciated. If I rebuild the motor, or do any major engine work on the car at-all, I'm going to keep it longer than the initial 10 month plan.

[240260280z]

This is a great read to help you: http://datsunzgarage.com/rebuild/index.htm

and this: http://www.biopatent.com/engine.html

btw: Black Dragon sell Grant Cast Piston Rings

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This is a great read to help you: http://datsunzgarage.com/rebuild/index.htm

and this: http://www.biopatent.com/engine.html

btw: Black Dragon sell Grant Cast Piston Rings

Thanks

[Arne]

My gut feel without seeing the car? From your description I'd say bag it. You might be able to rebuild your engine within your budget, but if so, only barely. These jobs are always more expensive than they first seem. And it sounds to me as if the rest of the car probably isn't worth the investment, unless you decide that you really like the ZX with automatic and are willing refresh it and keep it for a long while.

[LeonV]

The numbers are even cylinder-to-cylinder making me think gauge error, or the test was performed incorrectly. You don't even mention if the car runs or not. If it drives fine, then it is a test error. At 60psi, that engine would be extremely down on power. Something like cam timing can greatly affect cranking compression values across all cylinders.

If your compression is actually that low then I'd say the rings are the most likely to wear so evenly and drop compression. Perform a leak down test to be sure.

Worst case is the engine must be removed, best case is it's fine. Maybe you need to adjust cam timing to compensate for timing chain stretch, but that sure is a lot simpler than an engine rebuild.

[Gary in NJ]

I'm wondering if there is a way I can test whether it's the valves, or whether it's the rings that are leaking.

A leak down tester is the tool you are looking for. You'll need an air compressor to use this.

I'm with Leon on this, if the engine is running it sounds like test error.

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Yes, she runs .... Although, you have to push the pedal to the floor to get her to go anywhere, and while driving you can hear *POP*(s) at random. Which leads me to think it's blowby into the crankcase, or it's exhaust gases going passed poorly sealed valves.

I'll start this Saturday with a compression test of my own, and a leak down test. Hopefully I don't have to do the bottom end. In this book it says that defective piston rings make a chattering sound that is most noticeable during acceleration. I don't notice any sounds like that while driving, just lack of power and the popping noise.

Here's hoping it's not <em>too</em> broken...

[ezzzzzzz]

The leak down test is best but you can try this too. Warm the engine up to temp. Do a compression test on each cylinder noting the readings. Squirt about a table spoon of heavy oil into one cylinder at a time and retest that cylinder compression. A significantly higher reading indicates worn rings. Minimal change usually indicates bad valve guides and seals.

That said, you might go looking for another car in the $2000 price range. It would be easier to find a decent 280ZX in that range than an earlier Z. Keep yours for parts to sell, barter or use.

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ezzzzzzzzzz, Thanks for the advice, I actually just found this 280zx on Craigslist. .

http://sfbay.craigslist.org/eby/cto/2258209238.html Looks pretty decent to me, and hey; It's manual AND the engine is already rebuilt...

[borini63]

I think you have a timing issue!!

[Captain Obvious]

I think you have a timing issue!!

Haha! Speaking of timing issue...

You know this thread is like over three years dormant, right? :laugh: