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Discussion Starter · #1 ·
I did a compression test on my '83 280zxnt, and the results are pretty weird--I don't know what to make of them. The manual says 171 psi is normal, but my results range, on a more or less even gradient, from 181 psi on #6 cylinder to 198 psi on #1 cylinder. I've pulled the cylinder head off, and there's not that much carbon in the head or on the pistons. To add to the mix of weird things, #1 has had some difficulty in the past--even after replacing all six plugs, pulling #1 plug wire had no effect on the engine, even though I could see a spark between the wire and the distributor terminal while pulling it. The engine has had a rough idle at least since I first saw it. Any ideas about what's going on?

Another strange thing is that the cylinder head gasket doesn't actually cover the mating surface right around the cylinders, only around the outside. The metal in the area the gasket doesn't cover is slightly higher than the rest, so it and the gasket form a flat plane to hook up with the head. I have no prior experience with these engines, but it seems that a metal-to-metal contact would tend to leak between cylinders. Is this how it's supposed to be?
 

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Sounds like either the block or the head has been milled to increase the compression. I don't know of any practical way to confirm this, except maybe with a micrometer. Also, sounds like the #1 injector is bad or the connection is weak (also likely). The 280zx block does not normally have a metal ridge around each cylinder. There should be about a 1.5mm area around each cylinder that the gasket does not cover, 86mm bore, 89mm head gasket. Turbo engines are often prepped with a metal O-ring on the block or head to strengthen the seal, but I don't know why a non turbo Z would have this unless maybe it's to help with the higher compression.
 

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I agree with the previous comment by eboling about both the cause of the higher compression and the number one cylinder issue. One other thought on the compression - are you sure of the accuracy of your guage? You might try another to see if there is a difference.

Tom D.
 

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Discussion Starter · #4 ·
I don't know if the gauge is accurate, but it is new. What would I measure to check if it's been milled? Also, any thoughts on why I'm getting a gradient between #1 and #6?

BTW, a loose connection on the injector is a definite possibility, since the engine has had leaky injectors in the past, and the connectors don't look that good. Where could I get replacement connectors to solder/crimp on?
 

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Your local parts store carries the connectors, but you may have to order them since they usually don't keep many in stock. The price varies between about $6 and $13 each, depending on brand (Bosch is most expensive). You can also buy them online at www.advanceautoparts.com and probably other places. If your car still has the original connectors, I'd replace them all because they get loose and intermittent with age. There are 11 total (6 injectors plus CSV, thermotime switch, water temp sensor, air injector, and distributor advance).
 

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Well I owe you an apology for sending you on a wild goose chase. I could have sworn I saw it there about a month ago but I can't find it either. After searching online, the only site where I found it is:

http://catalog.eautopartscatalog.co...nnector&usemake=&appDescription=_any&usemake=

However, I can't figure out whose web site that is so it's not much good to you. When I bought my connectors, I went to two local parts stores (Vans and Pep Boys). Both places carried them but each only had 1 or two in stock and had to order the rest. Try calling your local parts houses and you'll probably get a hit. They came on blister-pack cards at one store and were behind the parts counter at the other and Vans even had two different brands of the same part. The ones I bought had the two wires already connected, but there is no rubber boot. I think the more expensive ones come with boots to keep the connections clean. The same connectors are used on lots of import cars, because they fit most (maybe all) fuel injectors made by Bosch. Good luck.
 
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