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gsgoingT

Probationary Member
13
0
Nov 14, 2007
urbandale, Iowa
my 91gsx has, from pass to driver side cylinder compression results 88,150,88,150. when I bought the car the valvecover bolts were loose not even tightened oil was leaking at the vc gasket, the car also came with 16g and manual boost valve. the car had no power it just drove as a nonturbo, I thought turbo was bad so I tried to check it out and when I detached the heathers there was a metal peace stuck inside the exhaust side of the turbo preventing turbo from working properly. I use this car as my daily comuter but I like it its awd so I'm trying to fix this compression problem, i'm trying to learn what should I expect with these compression results. I drove the car for a long time about a year I havent noticed any out of ordinary oil lacking when changing oil I take it as the car didn't burn oil. usually when changing oil there is always a bit less of old oil due to it's quality or whatever. the car does not smoke and runs just fine, there is also a clicking on passanger side of the engine at the very corner to the front of the car, so the corner closest to the front head light on the passanger side, other then that the car runs smooth. also at one day while driving I was at red light and at green i gassed it (when this happened I actually felt as if something sealed right and it now had the power) first 2nd 3rd gear and the car lost the power at the 4th gear and continued driving as it did before like a regular nonturbo car, though when I took off at light there was a giant black cloud behind, something that I never seen before nor again only at that time. I'm planing to do a valve job on this car so I wanted to see what are the possible parts that might be at failing with such compression results, and what might be of further use, I drive this car everyday so I'm not trying to make no batmobil or nothing like that, just fix it to work right. I appreciate any help and sorry about long ltr.
 
Low compression with no other engine failure symptom or driveability issues is normally caused by leaking exhaust valves, whether it be pitted valves or worn seats.

In the future, break your posts up a little using paragraphs so it's easier to read and respond to.
 
can I reuse my old valves and would valves from a nonturbo 2.0 work as well

as long as they are both 2.0 DOHC 4g63 heads you can swap the valves over

But you must have the valve face surfaced then you can lap the valve in if your going to be going cheap.

this will show you how a ground valve will look
http://www.dsmtuners.com/forums/newbie-forum/341288-why-have-your-valves-back-cut.html

then you can do this...
http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

make sure you check the head for flat
http://www.dsmtuners.com/forums/articles-engine-fuel/341627-how-check-head-warp.html


if it is warped you will need to have it surfaced...
DO NOT let the machine shop belt surface your head!!
http://www.dsmtuners.com/forums/cyl...0613-why-not-let-your-head-belt-surfaced.html

your head should look like this for mls or very close to this for a composite gasket
http://www.dsmtuners.com/forums/new...face-4g63t-cylinder-head-mls-head-gasket.html

your head should be measured for thickness before and after it is milled
New thickness is 5.200
if the head is thinner than 5.185 get a thicker head gasket to restore it to a height between 5.200-5.185
and you may want to do this oil port mod
http://www.dsmtuners.com/forums/newbie-forum/341028-4g63t-head-oil-port-mod.html
 
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