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Discussion Starter · #1 ·
Hello, i have some questions about a 2.6L trooper. I got this thing not too long ago for $700. Its a 90 5speed 4x4 and a 2.6L that is missing a bit. The owner told me it was probly a burnt valve but the motor still makes good power(i drove it home after buying it, about 14miles in town and trafic and it did awsome). Could this still be the case? I am planning a tune up (have all the parts in my shop) so a compresions check will tell me all i need to know about the valves right? And also how many PSI should a good cylinder hold? Anything to look out for when timing the motor? Thanks for help guys, this is my first injected motor i have ever worked on.
 

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You should definitely perform a compression test on your engine. You should see roughly 125 psi. from a good cyl. If your problem is a burnt valve, it'll most likely be Cyl. #3 exhaust valve. Also, have the cyl. head checked for cracks (if you need to remove the head for valve repair). '88 models had LOTS of problems with cracked heads and even some '89s... can't recall any problems with '90 but just be safe and get it checked out. If compression is good, you may have an ignition skip....if this is the case, make sure you use factory ign. parts (dist. cap, rotor, wires, and plugs)....have found aftermarket parts to be junk. Hope this helps.
 

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Discussion Starter · #3 ·
well im starting on the motor rebuild next week. I did a compression check when i changed the plugs. the comp check confirmed what you said, #3 had about 69psi dry and 90psi wet. The other 3 were around 100psi. So im thinking its time for a rebuild :lol:
 

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vinroc is absolutely correct regarding the head problems. my head gasket blew and after a bit of research on the 'net i discovered that it's pretty useless to even deal with the old head. i got a new AMC head with valves from aluminumheads.com (actually, i'm expecting it to arrive today). I don't remember where i found this info., but i read somewhere that the first bunch of heads for this engine were just made poorly...something about being poured from each end of the casting, so by the time the two ends met in the middle, there was a significant weak spot. i dunno about all that, but in any event, the heads on '88s are junk.
on a more positive note, my trooper has 168K and the A/C still blows cold and there's no oil getting by the piston rings, so that's pretty cool.
 

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Discussion Starter · #5 ·
are the 90 heads good? i dont have much money(the rebuild will be pushing it). Well thanks for help guys, as soon as i finish the front end rebuild on my 80 pick up the trooper gets some attnetion.
 

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Just an FYI: I have a '90 LS, and the head was replaced due to blown head gasket right before I bought it (~173,000). I would say check the milage on the engine before you use its head.

Just my .02
 

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You gotta get it right, brother. New truck and 3 new message boards. Look around in all the other places you've been posting... :lol: :wink:

Edit: Oh yeah, if you can afford it, go with a new head casting. That means cash, but peace of mind too.
 

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i've gotta a '90 and my head gasket let go around 160k on #3, go figure
decked and checked the head fine, blew the gasket a again 5k miles later
story=pulling out a blazer over 150 ft in soft hatteras sand (for 3rd time in a row) and blew my lower radiator hose
good news i can replace a head gasket blindfolded
 

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mepr said:
well im starting on the motor rebuild next week. I did a compression check when i changed the plugs. the comp check confirmed what you said, #3 had about 69psi dry and 90psi wet. The other 3 were around 100psi. So im thinking its time for a rebuild :lol:
You might also try a valve adjustment first. I know my '88 had one cylinder reading really low at one point. Valve adjustment fixed it, and gave it back a little pep as well.

Adam
 

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Discussion Starter · #11 ·
Well it failed emmsions so im just going to rebuild it. This will enshure its reliability anyway and give me a better idea of how it works :D
 
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