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Discussion Starter #1
saw this in my local paper
91 300zx twin turbo, 5sp, 95k, runs, low compression, $4k

I was wondering if what causes there could be any how major. I'm no dummy to engines just have no exp. with turbos. I can think of the standard rings, valves, head gasket. anything I'm missing?
 

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I'd just expect a complete overhaul. Internals, everything. Check it out and if everything else is in good shape (not too good of chance though, probably burnt out clutch, weak tranny, worn suspension parts) since low compression before even 100k miles means something was neglected in maint. IMO. Turbo's can still have life in them but in this case i doubt it. Just check if it boosts hard and any smoke coming out, or any particular noises associated with the turbos or the region in which they lie. Good luck!
 

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Here's some of answers I got

Author: MaxDoc (---.omaha.radiks.net)
Date: May 9, 7:32am

I always have a problem with heavily modded TTs or any Z32. That means the car was modded to be abused. But thats me. Anyhow I am always concerned with a "low" compression cylinder. Before buying the car check the compression of ALL cylinders. Actually a blown headgasket would be the best case scenario. Worst case is rings or valves. That is big bucks. Quantify what the dude calls "low" compression. The TT should have 171psi per cylinder with no more than 14psi variance between the cylinders. A TT will function with a range of 140-171 because it is forced inducted. TTs have a habit of "cooking" the #5 and #6 cylinder due to a casting flaw in the water jackets for these cylinders. Under normal driving this flaw usually does not cause problems. Now when the car is driven hard for any long period of time the temps in these two cylinders gets red hot and usually causes the rings to score the cylinders. This causes the low compression. Once that is done its re-build time and expect a bill of $3-4k. If this car has low compression on multiple cylinders either pass on it or subtract 3-4k from the market value of the car.
The compression test also needs to be done both dry and wet. Dry meaning a fully warmed up engine, all the plugs pulled, and at wide open throttle. Wet is the same but you ad about a tablespoon of oil to each cylinder then test. If the compression variance between wet and dry is over 20psi the rings are gone. If the compression remains basicly the same 3-8psi difference, its a valve train problem. If the compession is low on two side by side cylinders, its a headgasket.
MaxDoc
 

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low compression....either valve damage or bad rings. either way,youre talking an engine rebuild.BUT,if the body is straight,and the tranny and turbos are good,i still think its a steal at 4k.



Post Edited (Nov 11, 6:35pm)
 
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