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1983 720 4x4 King Cab Build Thread

Jon's AD3 720

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ok. im not loosing it i promise. i thought i already posted this issue. i let a friend borrow my truck and he drove it on the freeway at 70mph. i never take it over 55. now it is running rough and leaking a lot of oil. the oil is not coming from the top end as far as i can tell. no oil in the water and vise versa. replaced head gasket a year ago or so. it is a Z24 with a Z22 head. rear main maybe, but why is it running rough also? am i dealing with two problems or one? webber carb. i will look into front cover leaking as well as the sender. should i compression check?i was checking to see if a spark plug was not working by pulling plug wires one by one and didnt change how it runs. i have some dye that i can put in the oil that shows up under black light.  i can degrees and black light for the leak. does the leak explain  running rough though? any further advice?

Edited by Jon's AD3 720
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Sounds like a soon to be ex friend to me.  Unless it was a life or death run.


Front cover leaking?  Oil pressure sender vibrate loose?


Maybe stirred some junk in the tank up and got in carb?

Edited by bilzbobaggins
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Running it faster won't hurt it but internal parts will throw oil harder. Probably the valve cover gasket, maybe even at the back where it's hard to look. But I agree, power wash the engine and let it dry. Inspect often to see where it may be leaking.


Other places...


Oil pressure senders do fail and seep a little oil. It's on side of block above the oil filter and under the intake manifold.

Engine vent tube where it exits the side of the block behind the exhaust manifold.

Dip stick handle seal.


Most other gaskets will leak about the same no matter how fast you drive.



Running rough...

Combustion chambers and spark plugs will self clean themselves as you drive. If you normally drive slow and easy, deposits will build up and then if you really DRIVE it they will begin to shed and can even melt onto the porcelain forming a slightly conductive layer. They can even fuse across the plug gap and the plug not fire. You have dual plugs so the engine will run though not at the best. You can simply clean them and put back in.

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Running rough first look for vacuum leaks. The extra vibration may have been enough to loosen or crack a hose. Also Weber's are notorious for leaking at the base gaskets if not torqued properly. This is not a sign of engine failure this will probably be something small.

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I live just outside of Everett and have 2 720's currently. I would be happy to check yours out if you don't have any luck. I am almost obsessive with how many of these trucks I have worked on/owned! as far as vacuum leaks, any thing from the intake side of the head and on... the old trick with carb cleaner and spraying it on various parts is still a decent technique. 

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