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1984 nissan 720 4x4 head gasket repair


Cannabinoidgenes

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So this is my first post on ratsun. Last year I bought this truck. It ran poorly and could not hold an idle but I cleaned it up a bit and it improved. But I pulled a huge bone head move and took it for a long drive without checking my fluids. Turns out it was missing coolant over flow tank. Ran her outta coolant and blew the cap out of my head gaskets. I'm currently about to take the head off and figure how bad it is. But I want to make sure I don't screw up the timing. So I am just wondering how I set tdc in terms a newbie could undestand. I bought the power built wedge so the tensioner doesn't pop out by the way.

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Coolant over flow tank won't cause it to run dry. You have to check the rad yourself.

 

Take valve cover off and turn engine until the front two valves are closed and the cam lobes pointing downward at about 8 and 4 o'clock as viewed from the front.  Now take a look down near the alternator, at the timing scale where is is close to the rear pulley. You should find nearby a small notch on it. When the notch is on the 0 (zero) on the timing scale you are at TDC.

 

NOTE: To get the most accurate TDC, turn clockwise up to and stop at the mark. If you overshoot, back up well before and do it again. May take 3-4 tries.

 

Be sure to mark the chain and cam sprocket position so it goes back together on the same tooth.

 

First thing is take the battery out.

 

To save time leave the intake on the head and with help lift it off with the head. If you need to remove the intake it's way easier off the engine. The exhaust is easily unbolted and it can just stay with the truck. OR leave it on and you won't have to disconnect the EGR tube running between the exhaust and intake behind the head.

 

When the head comes off look for and save the two alignment dowels. You'll need them when assembling it.

 

s-l225.jpg

 

Head bolts are totally reusable if undamaged. Just wire brush clean.

 

Head gasket does not need re-torquing till the next tune up. Be sure engine is cold from sitting over night. It's easy, just loosen only one bolt at a time and tighten to 60 ft pounds. Only then move to the next bolt. You can do them front to back, side to side any way you like but only one bolt at a time.

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You can bump the engine around near to TDC, then switch to the crank shaft bolt and turn it by hand. Never try to turn the cam sprocket, it has to be the crank shaft. I think it's a 27mm.

 

If you turn the cam sprocket it will not move the crank shaft until all the slack is removed from the right side of the chain. This will move the cam timing to the crank shaft position way out of whack. To keep the cam timing correct, move the cam exactly how it is moved by the engine, and that is the crank shaft.

 

All timing chain slack MUST be on the right hand (passenger) side. If you over shoot the TDC position turning clockwise on the crank shaft, back well up counter clockwise and try again or you will introduce slack to the left side. 

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So I finally got the head off. It's pretty rusty in there. All surface rust of course. My main concern is between the 3rd and 4th cylinder where the gasket was blown there was a slight indent in the surface of the block.it doesn't go all the way through though. Should I just put the gasket on and see how it goes? What are my options here?

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The erosion is from driving 20,000 miles with it blown! If you put a gasket over this pit in the surface there's a good chance it will blow again. I would MIG a small blob of weld on there and carefully file or grind down flat. Not hard to do just picky work to get it flat. 

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Well I've decided I'm just going to get the head resurfaced and put her back together. And maybe get a thousand or so miles out of it while I fix my other cars head gasket. Which is damaged much less than this I'm sure. Then when that's fixed I'm just going to get a reman motor put in. I desperatley need a new clutch. Anyways the old ones just to worn and rusty for me to want to deal with it anymore. Lesson learned. I should be able to get her out of the garage soon. I'll post pictures once she's running.

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